Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Y Trechol – The Dominant Hills of Wales – Hill Reclassifications

Y Trechol –The Dominant Hills of Wales are the Welsh P30 hills whose prominence equal or exceed half that of their absolute height, accompanying the Dominant list is a sub list entitled The Lesser Dominant Hills of Wales with the criteria for this sub category being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list commenced publication on Mapping Mountains on 03.012.15 with its initial Introduction giving details to its compilation and criteria.  

The list is authored by Myrddyn Phillips and the posts that have appeared on Mapping Mountains detailing the additions, reclassifications and deletions to the Dominant and Lesser Dominant list appear below presented chronologically in receding order.

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Trostrey Hill (SO 369 051) – Dominant reclassified to Lesser Dominant (70th reclassification)

Summit Relocations post for Trostrey Hill

There has been a reclassification to the list of the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Trostrey Hill (SO 369 051)

The criteria for the list that this reclassification applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Trostrey Hill and it is adjoined to the Mynyddoedd Duon group of hills which are situated in the eastern part of South Wales (Region C, Sub-Region C3), and it is positioned with the Afon Wysg (River Usk) and the B4598 road to its west, the A40 road to its north, the A472 road to its south and the A449 road to its east, and has the village of Raglan towards the east north-east and the town of Brynbuga (Usk) towards the south.

When the original Welsh 100m P30 list was published on Geoff Crowder’s v-g.me website this hill was listed with a 199m summit height based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and which is adjoined to a triangulation pillar positioned at SO 36917 05185.

Extract from the Ordnance Survey 1:25,000 Explorer map

When the P30 lists were standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 136m of drop based on the 199m summit height and an estimated bwlch height of c 63m.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and gives a 62m spot height on the area of this hill’s bwlch positioned at SO 389 089, and when coupled with this hill’s 199m map summit height gave this hill 137m of drop.  These details were transferred to the Dominants list when first compiled, with these values giving this hill 68.84% dominance.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

Therefore, the reclassification of this hill from Dominant to Lesser Dominant status is due to LIDAR analysis, resulting in a 199.3m summit height and a 129.1m bwlch height, with these values giving this hill 70.2m of drop and 35.23% dominance.  With the 199.3m summit height taken to remaining natural ground with LIDAR also giving a 199.5m height positioned at SO 36920 05184 to a raised field boundary that is excluded from the height of this hill as it is considered a relatively recent man-made construct. 

The full details for the hill are:

Group:  Mynyddoedd Duon

Name:  Trostrey Hill

OS 1:50,000 map:  161

Summit Height:  199.3m (LIDAR)

Summit Grid Reference:  SO 36920 05188 (LIDAR)

Bwlch Height:  129.1m (LIDAR)

Bwlch Grid Reference:  SO 37462 05935 (LIDAR) 

Drop:  70.2m (LIDAR)

Dominance:  35.23% (LIDAR) 

Myrddyn Phillips (March 2020)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Coed y Bwnydd (SO 366 069) – Lesser Dominant reclassified to Dominant (69th reclassification)

Significant Name Changes post for Coed y Bwnydd

Summit Relocations post for Coed y Bwnydd

Significant Height Revisions post for Coed y Bwnydd

There has been a reclassification to the list of the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Coed y Bwnydd (SO 366 069)

The criteria for the list that this reclassification applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Coed y Bwnydd and it is adjoined to the Mynyddoedd Duon group of hills which are situated in the eastern part of South Wales (Region C, Sub-Region C3), and it is positioned with the Afon Wysg (River Usk) and the B4598 road to its west, the A40 road to its north and the A449 road to its east, and has the village of Raglan towards the east north-east and the town of Brynbuga (Usk) towards the south south-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the main P30 list under the name of Clytha Hill and listed with a 196m summit height, based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map at SO 368 069.

Extract from the Ordnance Survey 1:25,000 Explorer map

When the P30 lists were standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 68m of drop based on the 196m summit height and an estimated bwlch height of c 128m.  These details were transferred to the Dominants list when first compiled, with these values giving this hill 34.69% dominance.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and gives a second 196m spot height on the summit area of this hill and positioned at SO 367 069.  This additional 196m spot height also appears on Ordnance Survey data available on the Magic Maps website.

Extract from the Magic Maps website

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR summit image of Coed y Bwnydd

LIDAR bwlch image of Coed y Bwnydd

Therefore, the reclassification of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 201.4m summit height and a 59.4m bwlch height, with these values giving this hill 142.0m of drop and 70.50% dominance.  With the 201.4m summit height taken to the remains of an embankment which forms a part of an ancient hill fort and the 59.4m bwlch height taken to a road cutting, and as ancient summit structures deemed permanent in nature and the depth of road and rail cuttings qualify under the criteria used within this list the dominance is sufficient for this hill to be reclassified to Dominant status.

The full details for the hill are:

Group:  Mynyddoedd Duon

Name:  Coed y Bwnydd

OS 1:50,000 map:  161

Summit Height:  201.4m (LIDAR)

Summit Grid Reference:  SO 36613 06919 (LIDAR)

Bwlch Height:  59.4m (LIDAR)

Bwlch Grid Reference:  SO 39308 08901 (LIDAR)

Drop:  142.0m (LIDAR)

Dominance:  70.50% (LIDAR) 

Myrddyn Phillips (February 2020)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Ash Wood (SO 480 122) – Lesser Dominant reclassified to Dominant (68th reclassification)

Significant Name Changes post for Ash Wood

There has been a reclassification to the list of the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Ash Wood (SO 480 122)

The criteria for the list that this reclassification applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

The name the hill is now listed by is Ash Wood and this was derived from contemporary Ordnance Survey maps with the name of the bounded land where the summit of the hill is situated confirmed via the Tithe map.  The hill is adjoined to the Mynyddoedd Duon group of hills which are situated in the eastern part of South Wales (Region C, Sub-Region C3), and it is positioned with the B4233 road to its north-east and the A40 road to its south, and has the town of Trefynwy (Monmouth) towards the east.

When the original 200m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised with interpolated heights and drop values this hill was listed with an estimated c 101m of drop based on an estimated c 206m summit height and an estimated c 105m bwlch height, with these heights derived from interpolation of 5m contouring on the Ordnance Survey 1:25,000 Explorer map.  When the original Dominants list was compiled this hill was listed as a Lesser Dominant based on the detail given above which gave this hill 49.03% dominance.  These values were later amended to an estimated c 207m summit height and an estimated c 104m bwlch height, giving this hill c 103m of drop and 49.76% dominance.  

Extract from the Ordnance Survey 1:25,000 Explorer map

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

LIDAR summit image for Ash Wood

LIDAR bwlch image for Ash Wood

Therefore, the reclassification of Ash Wood from Lesser Dominant status is due to LIDAR analysis, resulting in a 206.4m summit height positioned at SO 48011 12229 and a 97.6m bwlch height positioned at SO 46851 13845, with the latter taken to a track cutting which complies with the criteria used within this list, with the caveat that the natural 105.6m high bwlch is intact and positioned at SO 46851 13803, with these values giving this hill 108.8m of drop and 52.69% dominance, which is sufficient for Dominant status.

The full details for the hill are:

Group:  Mynyddoedd Duon

Name:  Ash Wood

OS 1:50,000 map:  161

Summit Grid Reference:  SO 48011 12229 (LIDAR)

Summit Height:  206.4m (LIDAR)

Bwlch Grid Reference:  SO 46851 13845 (LIDAR)

Drop Summit to Bwlch:  108.8m (LIDAR)

Drop Bwlch to ODN:  97.6m (LIDAR)

Dominance:  52.69% (LIDAR)

Myrddyn Phillips (January 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pandy Bank (SJ 336 538) – Lesser Dominant addition (67th reclassification)

Survey post for Pandy Bank

There has been an addition to the list of the Y Trechol – The Dominant Hills of Wales, with the summit height and it location confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips on the 5^th April 2016, and the bwlch height and its location, the drop, dominance and status of the hill confirmed by LIDAR analysis initially conducted by Chris Crocker and subsequently by Myrddyn Phillips.

Pandy Bank (SJ 336 538)

The criteria for the list that this addition applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

The name the hill is Pandy Bank and it is adjoined to the Bryniau Clwyd group of hills, which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned with the B5425 road to its west and the A483 road to its east with the Afon Alun (River Alyn) to its west and east, and has the town of Wrecsam (Wrexham) towards the south.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the main P30 list as contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps of the day did not give the hill any contours of note.  The hill is the bi-product of mine spoil deposited from the Gresford Colliery and therefore the practice used in these two mapping scales is to show such land as a blank space on the map. 

Extract from the Ordnance Survey 1:25,000 Explorer map

The details for this hill were re-examined when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping has many spot heights not on other publicly available Ordnance Survey maps, and for the area taking in this hill it has contours at 5m intervals with an uppermost contour of 105m and bwlch contouring between 70m – 75m, with interpolation giving this hill an estimated c 34m of drop.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map

The details on the Ordnance Survey Vector Map Local prompted a survey conducted with the Trimble GeoXH 6000, resulting in a 105.4m summit height and when coupled with an estimated bwlch height of c 71m it gave this hill c 34m of drop and 32.61% dominance.

However, it was not until LIDAR became available that the details for the bwlch of this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Pandy Bank

Therefore, the addition of Pandy Bank to Lesser Dominant status is due to LIDAR bwlch analysis coupled with a Trimble GeoXH 6000 summit survey, resulting in a 105.4m summit height positioned at SJ 33630 53882 and a 70.2m bwlch height positioned at SJ 33704 53783, with these values giving this hill 35.1m of drop and 33.34% dominance, which is sufficient for Lesser Dominant status.

The full details for the hill are:

Group:  Bryniau Clwyd

Name:  Pandy Bank

OS 1:50,000 map:  117

Summit Grid Reference:  SJ 33630 53882

Summit Height:  105.4m (converted to OSGM15)

Bwlch Grid Reference:  SJ 33704 53783 (LIDAR)

Drop Summit to Bwlch:  35.1m (Trimble summit and LIDAR bwlch)

Drop Bwlch to ODN:  70.2m (LIDAR)

Dominance:  33.34% (Trimble summit and LIDAR bwlch)

For details on the summit survey of Pandy Bank

Myrddyn Phillips (December 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Dinas Powys (ST 148 722) – Dominant addition (66th reclassification)

Significant Height Revisions post for Dinas Powys

There has been an addition to the list of the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Dinas Powys (ST 148 722)

The criteria for the list that this addition applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name the hill is listed by is Dinas Powys and it is adjoined to the Bro Morgannwg group of hills, which are situated in the southern part of South Wales (Region C, Sub-Region C2), and it is encircled by a number of A roads, with the A4232 to its north, the A4050 to its west, the A4231 towards its south and the A4055 to its east, and has the town of Y Barri (Barry) to the south-west and the town of Penarth towards the east.

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it did not meet the criteria then used in the main P30 list. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 29m of drop based on a c 62m interpolated summit height and the 33m spot height that appears at the bwlch on Ordnance Survey 1:25,000 Explorer maps which for this area has contours at 5m intervals.

Extract from the Ordnance Survey 1:25,000 Explorer map

The details for this hill were re-examined when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping has many spot heights not on other publicly available Ordnance Survey maps.

Extract from the Ordnance Survey Vector Map Local

The details for this hill were also re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has contours at 5m intervals which are proving consistently more accurate compared to the 5m contours that sometimes appear on Ordnance Survey 1:25,000 Explorer maps and the online Vector Map Local.  These re-assessments resulted in the hill being listed with an estimated c 30m of drop with the interpolated summit height increasing from c 62m to c 63m.

Extract from the OS Maps website

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The addition of Dinas Powys to Dominant status is due to LIDAR analysis, resulting in a 69.4m summit height positioned at ST 14823 72225 and a 33.6m bwlch height positioned at ST 14757 72333, with these values giving this hill 35.8m of drop and 51.57% dominance, which is sufficient for this hill to be classified as a Dominant hill.

The full details for the hill are:

Group:  Bro Morgannwg

Name:  Dinas Powys

OS 1:50,000 map:  171

Summit Grid Reference:  ST 14823 72225 (LIDAR)

Summit Height:  69.4m (LIDAR)

Bwlch Grid Reference:  ST 14757 72333 (LIDAR)

Drop Summit to Bwlch:  35.8m (LIDAR)

Drop Bwlch to ODN:  33.6m (LIDAR)

Dominance:  51.57%

Myrddyn Phillips (November 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Ash Tip (ST 031 663) – Dominant addition (65th reclassification)

Significant Name Changes post for Ash Tip

Significant Height Revisions post for Ash Tip

There has been an addition to the list of the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Ash Tip (ST 031 663)

The criteria for the list that this addition applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name the hill is now listed by is Ash Tip and this was derived from local enquiry, and it is adjoined to the Bro Morgannwg group of hills, which are situated in the southern part of South Wales (Region C, Sub-Region C2), and it forms a part of landscaped ground that once made up the Aberthaw quarry and lime works, and it is positioned with the B4265 road to its north, and has the small community of Sain Tathan (St Athan) towards the north-west.

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in either the main P30 list or the Hills to be surveyed sub list, as contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps of the day showed the area that now makes up this hill as having no ring contours of note.

Extract from the Ordnance Survey 1:25,000 Explorer map

This area was re-examined when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has contours at 5m intervals and for the majority of land comprising old mine workings it shows present day contours, as opposed to the blank space showed on the counterparts of the 1:50,000 Landranger and 1:25,000 Explorer maps.

Extract from the OS Maps website

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The addition of Ash Tip to Dominant status is due to analysis of data on the OS Maps website coupled with LIDAR analysis and inspection of imagery on Google Maps and Google Earth with the conclusion that this hill is solid and stable.  LIDAR analysis has resulted in a 50.0m summit height and a 12.4m bwlch height, with these values giving this hill 37.6m of drop and 75.20% dominance, which is sufficient for the hill to be classified as a Dominant.

The full details for the hill are:

Group:  Bro Morgannwg

Name:  Ash Tip

OS 1:50,000 map:  170

Summit Grid Reference:  ST 03170 66338 (LIDAR)

Summit Height:  50.0m (LIDAR)

Bwlch Grid Reference:  ST 03298 66735 (LIDAR)

Drop Summit to Bwlch:  37.6m (LIDAR)

Drop Bwlch to ODN:  12.4m (LIDAR)

Dominance:  75.20%

Myrddyn Phillips (October 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Deg Erw Llandafin (ST 003 731) – Lesser Dominant deletion (64th reclassification)

Significant Name Changes post for Deg Erw Llandafin

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Deg Erw Llandafin (ST 003 731)

The criteria for the list that this deletion applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name the hill is now listed by is Deg Erw Llandafin and this was derived from the Tithe map, and it is adjoined to the Bro Morgannwg group of hills, which are situated in the southern part of South Wales (Region C, Sub-Region C2), and it is positioned with the A4222 and A48 roads to its north with minor roads to its west, south and east, and has the town of Y Bont-faen (Cowbridge) to the north-west.

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it did not meet the criteria then used in the main P30 list. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with a 67m summit height based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map which is positioned outside of the uppermost 65m ring contour and an estimated bwlch height of c 37m based on interpolation of 5m contouring between 35m – 40m, with these values giving this hill an estimated c 30m of drop and 44.78% dominance.

Extract from the Ordnance Survey 1:25,000 Explorer map

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping has additional spot heights not available on any other form of Ordnance Survey publicly available map and its larger dimension enabled easier study.  It was at this stage that the 67m spot height was considered erroneous and the drop of the hill was listed as an estimated c 29m.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The summit height produced by LIDAR analysis is 66.4m and is positioned at ST 00313 73177 and ST 00315 73179, and the bwlch height is 37.2m and is positioned at ST 00721 73222, with these values giving this hill 29.2m of drop which is insufficient for it to be considered for Lesser Dominant status.

The full details for the hill are:

Group:  Bro Morgannwg

Name:  Deg Erw Llandafin

OS 1:50,000 map:  170

Summit Grid Reference:  ST 00313 73177 & ST 00315 73179 (LIDAR)

Summit Height:  66.4m (LIDAR)

Bwlch Grid Reference:  ST 00721 73222 (LIDAR)

Drop Summit to Bwlch:  29.2m (LIDAR)

Drop Bwlch to ODN:  37.2m (LIDAR)

Dominance:  N/A, less than 30m of drop

Myrddyn Phillips (October 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Old Castle Down (SS 898 758) – Lesser Dominant deletion (63rd reclassification)

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR summit image of Old Castle Down (SS 898 758)

The criteria for the list that this deletion applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name of the hill is Old Castle Down and it is adjoined to the Bro Morgannwg group of hills, which are situated in the southern part of South Wales (Region C, Sub-Region C2), and it is positioned with the B4265 road to its west, a minor road to its south and the Afon Alun to its east, and has the small community of Saint-y-brid (St Bride’s Major) towards the south south-west.

When the original 100m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised and interpolated heights also included, this hill was listed with 34m of drop and 33.33% dominance, based on the 102m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and the 68m bwlch spot height that appears on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website for the summit

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website for the bwlch

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR bwlch image of Old Castle Down

The summit height produced by LIDAR analysis is 102.0m and is positioned at SS 89898 75814, and the bwlch height is 68.9m and is positioned at SS 90383 73586, with these values giving this hill 33.1m of drop and 32.44% dominance which is insufficient for its continued inclusion as a Lesser Dominant hill.

The full details for the hill are:

Group:  Bro Morgannwg

Name:  Old Castle Down

OS 1:50,000 map:  170

Summit Grid Reference:  SS 89898 75814 (LIDAR)

Summit Height:  102.0m (LIDAR)

Bwlch Grid Reference:  SS 90383 73586 (LIDAR)

Drop Summit to Bwlch:  33.1m (LIDAR)

Drop Bwlch to ODN:  68.9m (LIDAR)

Dominance:  32.44% (LIDAR)

Myrddyn Phillips (September 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pt. 65.9m (ST 352 947) – Dominant reclassified to Lesser Dominant (62nd reclassification)

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Pt. 65.9m (ST 352 947)

The criteria for the list that this reclassification applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

As I do not know an appropriate name for this hill either from historic research or local enquiry it is being listed by the point (Pt. 65.9m) notation, and it is adjoined to the Cymoedd Gwent group of hills, which are situated in the eastern part of South Wales (Region C, Sub-Region C2), and it is positioned with the A4042 road to the west and the A449 road to the east, and has the town of Caerllion (Caerleon) towards the south.

When the original 30-99m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised with interpolated heights and drop values this hill was listed with a 66m summit height based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 36m based on interpolation of 10m contouring between 30m – 40m, with these values giving this hill an estimated c 30m of drop.

Extract from the Ordnance Survey 1:25,000 Explorer map

When the original Dominants list was compiled this hill was listed as a Dominant based on detail on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.  This mapping has additional spot heights not available on any other form of Ordnance Survey publicly available map and in the case of this hill it has a bwlch spot height and 5m contouring.  The bwlch spot height is 33m and when coupled with the 66m summit spot height it gives this hill 33m of drop and 50.00% dominance. 

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

The reclassification of Pt. 65.9m from Dominant to Lesser Dominant status is due to LIDAR analysis, resulting in a 65.9m summit height and a 34.3m bwlch height, with these values giving this hill 31.6m of drop and 47.93% dominance.

The full details for the hill are:

Group:  Cymoedd Gwent

Name:  Pt. 65.9m

OS 1:50,000 map:  171

Summit Grid Reference:  ST 35225 94717 (LIDAR)

Summit Height:  65.9m (LIDAR)

Bwlch Grid Reference:  ST 35297 94949 (LIDAR)

Drop Summit to Bwlch:  31.6m (LIDAR)

Drop Bwlch to ODN:  34.3m (LIDAR)

Dominance:  47.93% (LIDAR)

Myrddyn Phillips (September 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Coed Cae Maen (ST 362 998) – Lesser Dominant deletion (61st reclassification)

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Coed Cae Maen (ST 362 998)

The criteria for the list that this deletion applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name the hill is now listed by is Coed Cae Maen and this was derived from the Tithe map, and it is adjoined to the Cymoedd Gwent group of hills, which are situated in the eastern part of South Wales (Region C, Sub-Region C2), and it is encircled by minor roads with the A472 road further to its north and the A449 road further to its east, and has the town of Brynbuga (Usk) towards its north-east.

When the original 100m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised and interpolated heights also included, this hill was listed with an estimated c 34m of drop and 33.66% dominance, based on an estimated c 101m summit height and an estimated bwlch height of c 67m, with these heights based on 10m contour intervals on the Ordnance Survey 1:25,000 Explorer map.

Extract from the Ordnance Survey 1:25,000 Explorer map

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The summit height produced by LIDAR analysis is 101.0m and is positioned at ST 36203 99841, and the bwlch height is 67.6m and is positioned at ST 35963 99882, with these values giving this hill 33.5m of drop and 33.12% dominance which is insufficient for its continued inclusion as a Lesser Dominant hill.

The full details for the hill are:

Group:  Cymoedd Gwent

Name:  Coed Cae Maen

OS 1:50,000 map:  171

Summit Grid Reference:  ST 36203 99841 (LIDAR)

Summit Height:  101.0m (LIDAR)

Bwlch Grid Reference:  ST 35963 99882 (LIDAR)

Drop Summit to Bwlch:  33.5m (LIDAR)

Drop Bwlch to ODN:  67.6m (LIDAR)

Dominance:  33.12% (LIDAR)

Myrddyn Phillips (August 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pt. 77.7m (ST 129 775) – Lesser Dominant addition (60th reclassification)

There has been an addition to the list of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Pt. 77.7m (ST 129 775)

The criteria for the list that this addition applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

As I do not know an appropriate name for this hill either from historic research or local enquiry it is being listed by the point (Pt. 77.7m) notation, and it is adjoined to the Cymoedd Morgannwg group of hills, which are situated in the central part of South Wales (Region C, Sub-Region C2), and it is encircled by minor roads with the Afon Elái (Ely River) to its south, and is positioned on the edge of Fairwater which is a district in the west of the city of Caerdydd (Cardiff).

This hill was not included in the main P30 list or the accompanying Hills to be surveyed sub list when the original Welsh 30-99m P30 hills were published on Geoff Crowder’s v-g.me website, as it was considered not to meet the criteria then used for this list.  This list has now been standardised with drop values and interpolated heights also included in the main P30 and the accompanying sub list.

Extract from the Ordnance Survey 1:25,000 Explorer map showing the summit of this hill

After this list was standardised with interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 26m of drop, based on its 77m summit spot height adjoined to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated bwlch height of c 51m based on interpolation of 5m contouring between 50m – 55m on the Ordnance Survey 1:25,000 Explorer map.  However, this mapping shows that the critical bwlch of this hill could be placed in one of two positions with the farthest position from its summit now being part of land that forms a dismantled railway cutting.   

Extract from the Ordnance Survey 1:25,000 Explorer map showing the bwlch of this hill

The details for this hill were re-examined when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has contours at 5m intervals and for the majority of land comprising old mine and quarry workings, and rail and road cuttings it shows present day continuous contours, as opposed to the broken contours on the 1:25,000 Explorer map.  This map has bwlch contours for this hill between 45m – 50m but its critical bwlch could still be placed in one of two positions.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR bwlch image of Pt. 77.7m

The confirmation of this hill’s addition to Lesser Dominant status is due to LIDAR analysis, resulting in a 77.7m summit height and a 44.4m bwlch height, with these values giving this hill 33.3m of drop and 42.82% dominance. 

The inclusion of this hill to Lesser Dominant status is dependent upon using the height of rail or road cuttings if lower on the hill to hill traverse in preference to the height and position of any natural col that may still exist. 

The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Pt. 77.7m

OS 1:50,000 map:  171

Summit Grid Reference:  ST 12931 77574 (LIDAR)

Summit Height:  77.7m (LIDAR)

Bwlch Grid Reference:  ST 11808 79174 (LIDAR)

Drop Summit to Bwlch:  33.3m (LIDAR) 

Drop Bwlch to ODN:  44.4m (LIDAR)

Dominance:  42.82% (LIDAR)

Myrddyn Phillips (August 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Mynydd Machen (ST 223 900) – Dominant deletion (59th reclassification)

There has been a deletion to a hill that is listed in the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Mynydd Machen (ST 223 900)

The criteria for the list that this deletion applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name of the hill is Mynydd Machen and it is adjoined to the Cymoedd Gwent group of hills, which are situated in the eastern part of South Wales (Region C, Sub-Region C2), and it is positioned with the A467 road to its north and the A468 road to its south, and has the town of Rhisga (Risca) towards its north-east.

When the original Welsh 300m height band of P30 hills published on Geoff Crowder’s v-g.me website were standardised with interpolated heights and drop values this hill was listed with an estimated c 193m of drop, based on the 362m summit spot height adjoined to a triangulation pillar on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated bwlch height of c 169m based on interpolation of 10m contouring between 160m – 170m.  Therefore, when the original Dominants list was compiled this hill was listed with 53.31% dominance.

Extract from the Ordnance Survey 1:25,000 Explorer map showing detail for Mynydd Machen

Extract from the Ordnance Survey 1:25,000 Explorer map showing detail for Mynydd y Grug

The details for this hill were re-assessed when it was noted that Mynydd y Grug (ST 177 906) which is an adjacent and connecting hill is given a 375m summit spot height on the Ordnance Survey Vector Map, however as this spot height applied to land that has been artificially raised from mine spoil a lengthy discussion developed on whether such a summit should be included in preference to a natural summit such as Mynydd Machen.  As artificially raised summits through mine spoil are included in the Dominants list if considered solid and stable, which that of Mynydd y Grug is, it meant that as Mynydd y Grug is now considered higher than Mynydd Machen their respective bylchau are swapped and their new drop values resulted in the deletion of Mynydd Machen from Dominant status.    

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Mynydd y Grug (ST 177 906)

LIDAR image for what was once the critical bwlch of Mynydd Machen and what is now the critical bwlch of Mynyd y Grug (bwlch positioned at ST 167 951)

The confirmation of this hill’s deletion from Dominant status is due to LIDAR analysis, resulting in a 363.2m summit height and a 250.6m bwlch height, with these values giving this hill 112.7m of drop and 31.01% dominance.  With LIDAR analysis of Mynydd y Grug resulting in a 374.2m summit height and a 169.85m bwlch height, with these values giving this hill 204.3m of drop and 54.61% dominance.

The full details for the hill are:

Group:  Cymoedd Gwent

Name:  Mynydd Machen

OS 1:50,000 map:  171

Summit Grid Reference:  ST 22381 90013 (LIDAR)

Summit Height:  363.2m (LIDAR)

Bwlch Grid Reference:  ST 19887 90335 (LIDAR)

Drop Summit to Bwlch:  112.7m (LIDAR)

Drop Bwlch to ODN:  250.6m (LIDAR)

Dominance:  31.01% (LIDAR)

Myrddyn Phillips (July 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Warren Hill (SS 736 940) – Dominant addition (58th reclassification)

There has been confirmation of an addition to the list of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Warren Hill

The criteria for the list that this addition applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name of the hill is Warren Hill and it is adjoined to the Cymoedd Morgannwg group of hills, which are situated in the central part of South Wales (Region C, Sub-Region C2), and it is encircled by major roads and a river with the A48 to its immediate north and the M4 to its immediate south and the Afon Nedd (River Neath) to its west, and has the town of Castell-nedd (Neath) towards its north.

This hill was not included in the original Welsh 30-99m height band of P30 hills published on Geoff Crowder’s v-g.me website, either in the main P30 or the Hills to be surveyed sub list, this was an oversight on my part as under the criteria used when this list was first compiled this hill qualified for the sub list.

Extract from the Ordnance Survey 1:25,000 Explorer map

The details for this hill were re-assessed after the sub list was standardised, and interpolated heights and drop values also included for the main P30 and the sub list, when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; this mapping is entitled the Interactive Coverage Map, and its larger scale enabled a better judgement for the drop value of this hill and it was subsequently included in the P30 list with an estimated c 31m of drop and 70.45% dominance.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The confirmation of this hill’s addition to Dominant status is due to LIDAR analysis, resulting in a 44.5m summit height and a 13.2m bwlch height, with these values giving this hill 31.3m of drop and 70.35% dominance.

The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Warren Hill

OS 1:50,000 map:  170

Summit Grid Reference:  SS 73667 94066 (LIDAR)

Summit Height:  44.5m (LIDAR)

Bwlch Grid Reference:  SS 73596 94201 (LIDAR)

Drop Summit to Bwlch:  31.3m (LIDAR) 

Drop Bwlch to ODN:  13.2m (LIDAR)

Dominance:  70.35% (LIDAR)

Myrddyn Phillips (June 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Mynydd y Glyn (ST 031 896) – Lesser Dominant reclassified to Dominant (57th reclassification)

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales, with the bwlch height and its location confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR bwlch image of Mynydd y Glyn

The criteria for the list that this reclassification applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name of the hill is Mynydd y Glyn and it is adjoined to the Cymoedd Morgannwg group of hills, which are situated in the central part of South Wales (Region C, Sub-Region C2), and it is positioned with the Afon Rhondda Fawr (Rhondda River) and the A4058 road to its north and the A4233 road to its west, and has the town of Pontypridd towards its east.

When the original Welsh 300m height band of P30 hills published on Geoff Crowder’s v-g.me website were standardised with interpolated heights and drop values this hill was listed with an estimated c 182m of drop, based on the 377m summit spot height and an estimated bwlch height of c 195m based on interpolation of 10m contouring between 190m – 200m that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

Summit extract from the Ordnance Survey 1:25,000 Explorer map

Bwlch extract from the Ordnance Survey 1:25,000 Explorer map

When the original Dominants list was compiled this hill was listed as a Lesser Dominant with 48.28% dominance based on the 377m summit height and the estimated c 182m drop value, as detailed above.

The drop value for this hill was next re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; this mapping is entitled the Interactive Coverage Map, and this resulted in the estimated drop value of c 182m remaining the same.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The reclassification of Mynydd y Glyn from Lesser Dominant to Dominant status is due to LIDAR bwlch analysis, with LIDAR not covering the summit of this hill, resulting in a 187.7m bwlch height, which when coupled with the 377m summit height gives this hill 189m of drop and 50.20% dominance.

The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Mynydd y Glyn

OS 1:50,000 map:  170

Summit Grid Reference:  ST 03193 89647

Summit Height:  377m

Bwlch Grid Reference:  ST 00330 90578 (LIDAR)

Drop Summit to Bwlch:  189m (LIDAR bwlch) 

Drop Bwlch to ODN:  187.7m (LIDAR)

Dominance:  50.20% (LIDAR bwlch)

Myrddyn Phillips (May 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pt. 63.3m (SH 491 760) – Lesser Dominant deletion (56th reclassification)

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales, with the bwlch height and its location confirmed by LIDAR analysis, and a subsequent summit survey with the Trimble GeoXH 6000 confirming its drop and status, both conducted by Myrddyn Phillips with the latter taking place on the 22^nd October 2018.

LIDAR image of Pt. 63.3m (SH 491 760)

The criteria for the list that this deletion applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The hill is now being listed by the point (Pt. 63.3m) notation as I do not know an appropriate name for it either from historic research or local enquiry.  The hill is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is encircled by minor roads with the B5420 to its south-west and the B5109 to its north-west, and has the town of Llangefni towards its west.

When the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the Hills to be surveyed sub list, as it did not at that stage meet the criteria used for the main P30 list. 

When the sub list was standardised, and interpolated heights and drop values also included for the P30 and sub list this hill was listed with an estimated c 30m of drop, based on the 64m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 34m based on interpolation of 5m bwlch contouring between 30m – 35m that appears on the Ordnance Survey 1:25,000 Explorer map.

Extract from the Ordnance Survey 1:25,000 Explorer map

When the original Dominants list was compiled this hill was listed as a Lesser Dominant with 46.875% dominance based on the 64m summit spot height and the estimated drop of c 30m.

The drop value for this hill was next re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; this mapping is entitled the Interactive Coverage Map, and the estimated drop value of c 30m remained the same.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR bwlch image of Pt. 63.3m (SH 491 760)

The deletion of Pt. 63.3m from Lesser Dominant status is due to LIDAR bwlch analysis and a subsequent summit survey with the Trimble GeoXH 6000 conducted by Myrddyn Phillips, resulting in a 63.3m summit height and a 35.1m bwlch height, with these values giving this hill 28.2m of drop which is insufficient for it to retain its Lesser Dominant status.

The Trimble GeoXH 6000 gathering data at the summit of Pt. 63.3m (SH 491 760)

The full details for the hill are:

Group:  Ynys Môn

Name:  Pt. 63.3m

OS 1:50,000 map:  114, 115

Summit Grid Reference:  SH 49157 76080

Summit Height:  63.3m (converted to OSGM15)

Bwlch Grid Reference:  SH 49043 76701 (LIDAR)

Drop Summit to Bwlch:  28.2m (Trimble summit and LIDAR bwlch)

Drop Bwlch to ODN:  35.1m (LIDAR)

Dominance:  N/A, insufficient drop (LIDAR)

For details on the summit survey of this hill

Myrddyn Phillips (May 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Coed Darcy (SS 711 955) – Lesser Dominant deletion (55th reclassification)

Significant Name Changes post for Coed Darcy

Significant Height Revisions post for Coed Darcy

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, its location, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Coed Darcy (SS 711 955)

The criteria for the list that this reclassification applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name the hill is listed by is Coed Darcy and it is adjoined to the Fforest Fawr group of hills, which are situated in the northern part of South Wales (Region C, Sub-Region C2), and it is positioned with the B4290 and M4 roads to its east, and has the town of Castell-neth (Neath) towards the north-east.

When the original 30—99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill appeared in the accompanying Hills to be surveyed sub list as it did not meet the criteria then used for the main P30 list; however this sub list has now been standardised with drop values and interpolated heights also included in the main P30 and the accompanying sub list.

After this list was standardised and interpolated heights also included this hill was listed with 31m of drop and 37.35% of dominance, based on the 83m summit spot height that appears on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map and a bwlch height of 52m based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

However, it was not until LIDAR became available that the details for this hill were next re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The summit height produced by LIDAR analysis is 80.4m and is positioned at SS 71147 95565, and the bwlch height is 53.0m and is positioned at SS 71330 95324, with these values giving this hill 27.4m of drop which is insufficient for consideration for either Dominant or Lesser Dominant status.

The full details for the hill are:

Group:  Fforest Fawr

Name:  Coed Darcy

OS 1:50,000 map:  170

Summit Grid Reference:  SS 71147 95565 (LIDAR)

Summit Height:  80.4m (LIDAR)

Bwlch Grid Reference:  SS 71330 95324 (LIDAR)

Drop Summit to Bwlch:  27.4m (LIDAR)

Drop Bwlch to ODN:  53.0m (LIDAR)

Dominance:  N/A, insufficient drop (LIDAR)

Myrddyn Phillips (March 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pantau (SN 648 226) – Lesser Dominant deletion (54th reclassification)

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, its location, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Pantau

The criteria for the list that this reclassification applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

When the original Welsh 100m P30 list that was published on Geoff Crowder’s v-g.me website was standardised and interpolated height and drop vales added, this hill was listed with c 41m of drop based on an estimated c 118m summit height and an estimated c 77m bwlch height.

These values were re-assessed when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online, and this map gives this hill a 117m summit spot height and a 77m spot height on the area of its bwlch, with these values giving this hill 40m of drop and 34.19% dominance.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

The name of the hill is Pantau and it is adjoined to the Y Mynydd Du group of hills, which are situated in the north-western part of South Wales (Region C, Sub-Region C1), and it is positioned with the Afon Tywi (River Towy) and the A40 road to its north-west, and has the small town of Llandeilo towards the west.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of designated open access land and has no public footpaths that approach it, for those wishing to do so an approach from the convenience of a minor road towards the south may be the best option.

The summit height produced by LIDAR analysis is 115.8m and is positioned at SN 64809 22669 and SN 64816 22665, and the bwlch height is 77.3m and is positioned at SN 65097 22612, with these values giving this hill 38.6m of drop and 33.31% dominance, which is insufficient for this hill to be classified as a Lesser Dominant.

The full details for the hill are:

Group:  Y Mynydd Du

Name:  Pantau

OS 1:50,000 map:  159

Summit Grid Reference:  SN 64809 22669 and SN 64816 22665 (LIDAR)

Summit Height:  115.8m (LIDAR)

Bwlch Grid Reference:  SN 65097 22612 (LIDAR)

Drop Summit to Bwlch:  38.6m (LIDAR)

Drop Bwlch to ODN:  77.3m (LIDAR)

Dominance:  33.31% (LIDAR)

Myrddyn Phillips (February 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Cae Ddu Main (SN 622 983) – Lesser Dominant addition (53rd reclassification)

Significant Name Changes post for Cae Ddu Main

Summit Relocations post for Cae Ddu Main

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, its location, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cae Ddu Main

The criteria for the list that this reclassification applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

When the original Welsh 100m P30 list was published on Geoff Crowder’s v-g.me website the summit location of this hill was given to the 102m spot height that is positioned at SS 619 984 on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps.  When this list was standardised with interpolated height and drop values included this hill was listed with c 30m of drop based on the 102m spot height, with these values insufficient for Lesser Dominant status.  However, the 1:25,000 Explorer map has a small uppermost 105m ring contour to the east of the 102m spot height, which prompted the summit relocation of this hill.

The name of the bounded land where the summit of this hill is situated is Cae Ddu Main and this was derived from the Tithe map, and it is this name that the hill is now listed by.  The hill is adjoined to the Mynydd Penlle’rcastell group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and is positioned with the A483 road to its immediate west and the A48 and M4 to its north, and has the village of Penlle’r-gaer to its north.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of designated open access land, for those wishing to do so an approach from the north may be feasible.

LIDAR summit image of Cae Ddu Main

The summit height produced by LIDAR analysis is 106.9m to remaining natural ground and is positioned at SN 62212 98337, this position is approximately 290 metres east from where the summit was originally listed at the position of the 102m spot height, with the height produced by LIDAR to the natural bwlch being 69.1m positioned at SN 62051 00000, with these values giving this hill 37.8m of drop and 35.34% dominance, which is sufficient for this hill to be classified as a Lesser Dominant.

LIDAR bwlch image of Cae Ddu Main

The full details for the hill are:

Group:  Mynydd Penlle’rcastell

Name:  Cae Ddu Main

OS 1:50,000 map:  159

Summit Grid Reference:  SN 62212 98337 (LIDAR, remaining natural high point)

Summit Height:  106.9m (LIDAR, remaining natural high point)

Bwlch Grid Reference:  SN 62051 00000 (LIDAR, natural bwlch)

Drop Summit to Bwlch:  37.8m (LIDAR)

Drop Bwlch to ODN:  69.1m (LIDAR, natural bwlch)

Dominance:  35.34% (LIDAR)

Myrddyn Phillips (February 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Bryn (SH 426 361) – Dominant addition (52nd reclassification)

Survey post for Bryn

Significant Name Changes post for Bryn

Summit Relocations post for Bryn

There has been confirmation of an addition to the list of Y Trechol – The Dominant Hills of Wales, with the P30 status that initiated this addition suggested by Chris Pearson in February 2018 and its P30 status confirmed by LIDAR analysis conducted by Chris Crocker.  The hill was subsequently analysed using LIDAR and surveyed with the Trimble GeoXH 6000 by Myrddyn Phillips, with the latter taking place on the 10^th September 2018.

LIDAR image of Bryn

The criteria for the list that this addition applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

When the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill appeared in the accompanying Hills to be surveyed sub list as it did not meet the criteria then used for the main P30 list; however this sub list has now been standardised with drop values and interpolated heights also included in the main P30 and the accompanying sub list.

When this list was standardised and interpolated heights also included this hill was listed with an estimated c 28m of drop, based on the 36m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 8m based on interpolation of bwlch contouring between 0 – 10m. 

Extract from the Ordnance Survey 1:25,000 Explorer map

These values were re-evaluated when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online, and as this map has 5m contour intervals the bwlch contouring was reassessed.  However, as there is a rail line passing through this bwlch the contours on this map are not continuous and could in affect be between 0 – 5m or between 5m – 10m at the critical point of the bwlch, they were taken as being between 5m – 10m with an estimated c 7m height for the bwlch, giving this hill c 29m of drop which is still insufficient to consider for Dominant status.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

The locally known name of the hill is Bryn, and this is the name it is now listed by, and it is adjoined to the Pen Llŷn group of hills, which are situated in the western part of North Wales (Region A, Sub-Region A1), and is positioned overlooking the sea to its south and the A 497 road to its north, and has the town of Pwllheli towards the west.

As the summit of this hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so a public footpath approaches the hill from its north and access to the summit is relatively easy from here via its north-west which avoids the majority of gorse on its upper slopes.

Prior to the Trimble GeoXH 6000 survey this hill’s summit and bwlch contours were analysed with LIDAR, with the conclusion that the hill is not a natural P30 as LIDAR bwlch contouring implies that the natural bwlch would once have been over 7m in height.  This bwlch is now reduced in height due to a railway cutting.

An appropriate name for the hill was also researched via the Tithe map, finding that the upper section of the hill which now comprises one field, used to comprise two, with the boundary between each showing as a slight elevation on LIDAR.  This boundary although old, is not ancient, and would be a man-made construction.  LIDAR also shows that the natural summit of this hill still exists, close to the old field boundary.  Therefore I wanted to take data sets from the slightly raised field boundary, and the natural summit with LIDAR giving two potential positions for this, with one adjacent to the old field boundary and the other a few metres distant from it.

                                                                  

LIDAR image of Bryn with the old raised field boundary on the right

Therefore, three data sets were taken with the Trimble GeoXH 6000 from the summit area of this hill, resulting in:

1^st survey:  36.750m at SH 42673 36171 (raised old field boundary)

2^nd survey:  36.5965m at SH 42668 36171 (average of two surveys)

3^rd survey:  36.675m at SH 42656 36173 (natural summit)

Therefore, the height produced by the Trimble GeoXH 6000 survey to the natural summit of this hill is 36.7m and is positioned at SH 42656 36173, with LIDAR analysis giving a 6.6m bwlch height positioned at SH 43103 36535, with these values giving this hill 30.0m of drop and 81.88% dominance, these values confirm this hill’s addition to Dominant status.

Gathering data with the Trimble GeoXH 6000 at the summit of Bryn

The full details for the hill are:

Group:  Pen Llŷn

Name:  Bryn

OS 1:50,000 map:  123

Summit Height:  36.7m (converted to OSGM15) (natural summit)

Summit Grid Reference:  SH 42656 36173 (natural summit)

Bwlch Height:  6.6m (LIDAR)

                                      

Bwlch Grid Reference:  SH 43103 36535 (LIDAR)

Drop Summit to Bwlch:  30.0m (Trimble summit and LIDAR bwlch)

Drop Bwlch to ODN:  6.6m (LIDAR)

Dominance:  81.88%

My thanks to Chris Pearson for suggesting this hill as a P30 and to Chris Crocker for initial LIDAR analysis

For details on the survey that confirmed the Dominant status of this hill

Myrddyn Phillips (February 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Cae Ffwyn Uchaf (SN 588 005) – Dominant reclassified to Lesser Dominant (51st reclassification)

Significant Name Changes post for Cae Ffwyn Uchaf

Summit Relocations post for Cae Ffwyn Uchaf

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, its location, drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cae Ffwyn Uchaf

The criteria for the list that this reclassification applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

Prior to LIDAR analysis this hill was listed with 50.75% dominance based on a c 34m drop value, with a 67m summit spot height on the Ordnance Survey 1:50,000 Landranger map and an estimated bwlch height of c 33 based on interpolation of bwlch contouring between 30m – 35m.

The bounded land where the summit of this hill is situated is named Cae Ffwyn Uchaf on the Tithe map and this is the name the hill is now listed by.  The hill is adjoined to the Mynydd Penlle’rcastell group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and is positioned with the B4296 immediately to its east with the M4 and the Afon Lliw beyond, and has the town of Gorseinon towards the south.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of designated open access land, for those wishing to do so the summit is positioned relatively close to a B road which could give access towards the summit from its east.

The reclassification of Cae Ffwyn Uchaf to Lesser Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.   The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The DTM LIDAR analysis gives the hill the following details:

Name:  Cae Ffwyn Uchaf

Summit Height:  66.6m

Summit Grid Reference:  SN 58825 00532

Bwlch Height:  36.0m (natural bwlch)

Bwlch Grid Reference:  SN 59731 00951 (natural bwlch)

Drop:  30.6m

Dominance:  45.90%

LIDAR bwlch image of Cae Ffwyn Uchaf

Therefore, the 66.6m LIDAR analysis for the summit position at SN 58825 00532 and the 36.0m LIDAR analysis for the bwlch position at SN 59731 00951 gives this hill 30.6m of drop and 45.90% dominance, which is insufficient for its continued Dominant status, with LIDAR also giving a 65.9m height at SS 58625 99765 which is to the old listed summit of this hill.

LIDAR image of the old listed summit at SS 58625 99765

The full details for the hill are:

Group:  Mynydd Penlle’rcastell

Name:  Cae Ffwyn Uchaf

OS 1:50,000 map:  159

Summit Grid Reference:  SN 58825 00532 (LIDAR)

Summit Height:  66.6m (LIDAR)

Bwlch Grid Reference:  SN 59731 00951 (LIDAR, natural bwlch)

Drop Summit to Bwlch:  30.6m (LIDAR)

Drop Bwlch to ODN:  36.0m (LIDAR, natural bwlch)

Dominance:  45.90% (LIDAR)

Myrddyn Phillips (February 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Brandy Hill (SN 213 133) and Castell Meherin (SN 146 117) – Dominant re-twinning (50th reclassification)

Survey post for Brandy Hill

Survey post for Castell Meherin

Significant Name Changes post for Castell Meherin

Approaching the summit of Brandy Hill

The summit of Castell Meherin

There has been a re-twinning of two hills in the Y Trechol – The Dominant Hills of Wales list, with their summit height, their location and drop initially confirmed by LIDAR analysis and subsequently by summit surveys with the Trimble GeoXH 6000 which were conducted by Myrddyn Phillips, with the latter taking place on the 1^st August 2018.

The criteria for the listing that this re-twinning applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those addition Welsh P30 hills whose prominence is 33.33% or more and below 50% of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

When the Y Trechol - The Dominant Hills of Wales list was first compiled these two hills were listed as twin summits based on their 205m summit heights on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and which are both adjoined to triangulation pillars.

Extract from the Ordnance Survey 1:25,000 Explorer map

Extract from the Ordnance Survey 1:25,000 Explorer map

The two summits are a part of the Brandy Hill group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and are positioned with the A 477 road to their south, and the A 40 road to their north, with the B 4328 nearer and to the summit of Brandy Hill to its north-west and the B 4314 nearer and to the summit of Castell Meherin to its north.

These two hills were then separated and de-twinned based on the flush bracket heights adjoined to their trig pillars, resulting in Brandy Hill being listed as the higher hill and therefore the hill included in the Dominants list.  The flush bracket height for each hill is given below:

Brandy Hill:  206.047m at SN 21342 13381

Castell Meherin:  205.258m at SN 14646 11773

However, the trig pillar on Brandy Hill is positioned on a raised embankment that forms part of a field boundary.  Whereas the trig pillar on Castell Meherin is positioned on the raised embankment of an ancient hill fort.  As raised field boundaries are considered a recent man-made construct and not a part of the natural height of a hill and ancient hill forts are considered as permanent in nature and now a part of the hill, the highest natural ground at the base of the field boundary on Brandy Hill was taken for the height of this hill, and this is also where LIDAR analysis places this hill’s summit, whereas ground at the base of the trig pillar on Castell Meherin was taken as the height of this hill’s summit.  The results of each Trimble survey and their measurement offsets are given below:

Brandy Hill:  205.477 – 0.40m offset = 205.077m

Castell Meherin:  206.257m – 1.18m offset = 205.077m

Remarkably the Trimble GeoXH 6000 gave the height of each hill as equal to the nearest millimetre.  However, although these hills are now considered as Dominant twin summits, Brandy Hill is being prioritised for the drop value given in the 200m Twmpau list and the values associated with this are also given below.      

Gathering data at the summit of Brandy Hill

Gathering data at the summit of Castell Meherin

Therefore, as the Trimble GeoXH 6000 survey resulted in each summit having the same 205.077m height Brandy Hill and Castell Meherin are now re-twinned.

The full details for each hill are:

Group:  Brandy Hill

Name:  Brandy Hill

OS 1:50,000 map:  158

Summit Grid Reference:  SN 21352 13359

Summit Height:  205.1m (converted to OSGM15)

Bwlch Grid Reference:  SN 14049 17973 (LIDAR)

Drop Summit to Bwlch:  151.6m (Trimble summit and LIDAR bwlch)

Drop Bwlch to ODN:  53.5m (LIDAR)

Dominance:  73.92% (Trimble summit and LIDAR bwlch)

Group:  Brandy Hill

Name:  Castell Meherin

OS 1:50,000 map:  158

Summit Grid Reference:  SN 14646 11773

Summit Height:  205.1m (converted to OSGM15)

Bwlch Grid Reference:  SN 18517 12805 (LIDAR, natural bwlch)

Drop Summit to Bwlch:  42.8m (Trimble summit and LIDAR bwlch)

Drop Bwlch to ODN:  162.2m (LIDAR, natural bwlch)

Dominance:  20.89% (Trimble summit and LIDAR bwlch)

For details on the survey of Brandy Hill

For details on the survey of Castell Meherin

Myrddyn Phillips (January 2019)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

THIS HILL HAS SUBSEQUENTLY BEEN DELETED FROM LESSER DOMINANT STATUS

Mynydd Pencarreg (SN 575 432) – Lesser Dominant addition (49th reclassification)

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to a combination of LIDAR analysis conducted by Aled Williams and a summit survey with the Trimble GeoXH 6000 conducted by Myrddyn Phillips, with the latter taking place on the 31^st July 2018.

The summit of Mynydd Pencarreg (SN 575 432)

The criteria for the list that this reclassification applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those addition Welsh P30 hills whose prominence is 33.33% or more and below 50% of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

Prior to LIDAR analysis and the summit survey with the Trimble GeoXH 6000 this hill was listed with an estimated c 138m of drop based on the 415m summit height given to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated bwlch height of c 277m based on interpolation of bwlch contouring between 270m – 280m on these two maps and partial 5m contouring that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, with these values giving this hill 33.25% dominance.

                               

The name of the hill is Mynydd Penycarreg and it is the highest hill in own grouping of hills, which are situated in the central part of Mid and West Wales (Region B, Sub-Region B2), and it is positioned between the B 4337 road to the south-west and the A 482 road towards the north-east, and has the town of Llanbedr Pont Steffan (Lampeter) towards the north.

As the summit of the hill is a part of designated open access land permission to visit does not have to be sought, however this open access land is almost an island without any public footpaths leading to it and with only one recognised access point from a minor road to the south-west of the summit.

The addition of Mynydd Pencarreg to Lesser Dominant status is due to LIDAR analysis conducted by Aled Williams coupled with a Trimble GeoXH 6000 summit survey conducted by Myrddyn Phillips.   The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

The survey with the Trimble produced a summit height of 414.9m (converted to OSGM15), whilst the LIDAR analysis produced a bwlch height of 276.2m, with these values giving this hill 138.7m of drop and 33.43% dominance, which confirms its addition to Lesser Dominant status.

The Trimble GeoXH 6000 gathering data at the summit of Mynydd Pencarreg

The full details for the hill are:

Group:  Mynydd Pencarreg

Name:  Mynydd Pencarreg

OS 1:50,000 map:  146

Summit Grid Reference:  SN 57560 43215

Summit Height:  414.9m (converted to OSGM15)

Bwlch Grid Reference:  SN 60011 44082 (LIDAR)

Drop Summit to Bwlch:  138.7m (Trimble summit and LIDAR bwlch)

Drop Bwlch to ODN:  276.2m (LIDAR)

Dominance:  33.43% (Trimble summit and LIDAR bwlch)

For details on the summit survey of this hill

Myrddyn Phillips (December 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Five Acres (SS 537 932) – Lesser Dominant deletion (48th reclassification)

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With an accompanying sub list entitled Y Trechol - The Lesser Dominant Hills of Wales, with the criteria for this sub category being those additional Welsh P30 hills whose prominence is 33% or more and below 50% of their absolute height.

Prior to LIDAR analysis this hill was listed with 33.86% dominance based on an estimated c 43m drop value, with an estimated c 127m summit height based on an uppermost 125m ring contour and an estimated c 84m bwlch height based on interpolation of 5m contouring between 80m – 85m on the Ordnance Survey 1:25,000 Explorer map. 

Extract from the Ordnance Survey 1:25,000 Explorer map

The bounded land where the summit of this hill is situated is named Five Acres on the Tithe map and this is the name the hill is now listed by.  The hill is adjoined to the Gŵyr group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and is positioned between the B roads of the 4295 to the north-west and 4271 to the south, and has the village of Pen-clawdd towards the north.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of designated open access land, for those wishing to do so the nearest public footpath is to its south, with other possibilities via gated fields to the east.

The deletion of Five Acres from Lesser Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.   The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of the summit of Five Acres with the natural summit shown and the field boundary's being prominent on the image

LIDAR image of Five Acres

The 1m DTM LIDAR analysis gives the hill the following details:

Name:  Five Acres

Summit Height:  125.1m (natural summit)

Summit Grid Reference:  SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297 (natural summit) (LIDAR gives a 125.2m high raised field boundary positioned at SS 53791 93318 which is considered a relatively recent man-made construct)

Bwlch Height:  84.3m

Bwlch Grid Reference:  SS 56307 93757

Drop:  40.8m

Dominance:  32.59%

Therefore, the 125.1m LIDAR analysis for the summit gives four positions of equal height at SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297 and the 84.3m LIDAR analysis for the bwlch position at SN 56307 93757 gives this hill 40.8m of drop and 32.59% dominance, with is insufficient for Lesser Dominant status.

The full details for the hill are:

Group:  Gŵyr

Name:  Five Acres

Dominance:  32.59% (LIDAR)

OS 1:50,000 map:  159

Summit Grid Reference:  SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297 (LIDAR) 

Summit Height:  125.1m (LIDAR)

Bwlch Grid Reference:  SS 56307 93757 (LIDAR)

Drop Summit to Bwlch:  40.8m (LIDAR)

Drop Bwlch to ODN:  84.3m (LIDAR)

Myrddyn Phillips (November 2018)






Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Cae (SN 560 038) – Lesser Dominant deletion (47th reclassification)

Significant Name Changes post for Cae

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cae (SN 560 038)

The criteria for the list that this addition applies to are: 

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Cae and this was derived from the Tithe map, and it is adjoined to the Mynydd Sylen group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and is positioned between the stream valleys of the Afon Morlais to its west and the Afon Gwili to its east, and has the towns of Llanelli to the south-west and Pontarddulais to the east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list with a 119m summit height, based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.

 

Extract from the Ordnance Survey 1:25,000 Explorer map

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 40m of drop, based on the 119m summit spot height and an estimated c 79m bwlch height, based on interpolation of 5m contouring between 75m – 80m, resulting in a dominance value of 33.61%, which was sufficient for Lesser Dominant status.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.  

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 119.0m summit height and an 80.0m bwlch height, with these values giving this hill 39.0m drop and 32.79% dominance, which is insufficient for Lesser Dominant status.

The full details for the hill are:

Group:  Mynydd Sylen

Name:  Cae

OS 1:50,000 map:  159

Summit Height:  119.0m (LIDAR)

Summit Grid Reference:  SN 56069 03819 (LIDAR)

Bwlch Height:  80.0m (LIDAR)

Bwlch Grid Reference:  SN 55961 04021 (LIDAR)

  

Drop:  39.0m (LIDAR)

Dominance:  32.79% (LIDAR)

Myrddyn Phillips (November 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Hidden Slabs Stack (SS 119 982) – Dominant deletion (46th reclassification)

There has been confirmation of a deletion to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

This hill was included in the original Welsh P30 lists that were published on Geoff Crowder’s v-g.me website and given an estimated summit height of c 30m.  When these P30 lists were standardised and interpolated heights and drop values also included this hill was listed with c 30m of drop and when the Dominant list was originally compiled this hill was listed with 100.00% dominance.

When compiling the original Welsh P30 lists I contacted Dave Viggers in relation to sea stacks positioned around the Pembrokeshire coast, regarding their height, location and name.  Dave is now a Vice President of the Climber’s Club and gave me information including the location of this hill, its approximate height and its name, which he advised was known as Hidden Slabs Stack.  However, site visits to this location by a number of people including Jon Glew, Douglas Law, Rob Woodall and Adrian Rayner have brought in to doubt the existence of a prominent sea stack at this point, and if anything did exist its prominence was estimated to be far lower than the listed c 30m.  

The name of this hill is Hidden Slabs Stack, and as its name and LIDAR analysis implies it is a sea stack.  The hill is adjoined to the Brandy Hill group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and is positioned with the coast to its immediate south and has the A 4139 road and the small community of Penally to its north-west.

If wanting to visit this hill permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so the Pembrokeshire Coast Path is positioned to the north of the hill, but caution is advised as the easiest approach may necessitate some form of climbing.

The confirmation of the deletion of Hidden Slabs Stack from Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 2m DTM LIDAR image of Hidden Slabs Stack

The 1m DSM LIDAR image of Hidden Slabs Stack

The 1m DSM LIDAR analysis gives the hill the following details:

Name:  Hidden Slabs Stack

Summit Height:  6.5m

Summit Grid Reference:  SS 11902 98247

Bwlch Height:  N/A

Bwlch Grid Reference:  N/A

Drop:  6.5m

Dominance:  not applicable as under 30m prominence

Therefore, the 6.5m LIDAR analysis for the summit position at SS 11902 98247 gives this hill 6.5m of drop, which is insufficient for Dominant status.

LIDAR image of the summit of Hidden Slabs Stack

The full details for the hill are:

Group:  Brandy Hill

Name:  Hidden Slabs Stack

Dominance:  not applicable as under 30m prominence

OS 1:50,000 map:  158

Summit Grid Reference:  SS 11902 98247 (LIDAR)

Summit Height:  6.5m (LIDAR)

Bwlch Grid Reference:  N/A

Drop Summit to Bwlch:  6.5m (LIDAR)

Drop Bwlch to ODN:  N/A

Myrddyn Phillips (October 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

No Name Stack (SR 975 932) – Dominant deletion (45th reclassification)

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

Prior to LIDAR analysis this hill was listed with 30m of drop based on the 30m spot height that appears on the Ordnance Survey 1:25,000 Explorer map, with the height of the bwlch accepted as that for Ordnance Datum Newlyn (sea level), however map data indicates that this hill is adjoined to the mainland and is not tidal, indicating that its status as a P30 was debatable.

When the original Welsh P30 lists were compiled I contacted Dave Viggers in relation to sea stacks positioned around the Pembrokeshire coast, regarding their height, location and name.  Dave is now a Vice President of the Climber’s Club and gave me invaluable information including the location of this hill, its approximate height and its name, which he advised was known as No Name Stack.

Although the name of this hill implies that it is a sea stack, it is adjoined to the mainland.  The hill is adjoined to the Brandy Hill group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and is positioned with the coast to its immediate south-east and has St Govan’s Head to its south and Broad Haven towards its north north-east, and has the village of Bosherston towards its north-west.

If wanting to visit this hill permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so caution is advised as the easiest approach will necessitate some form of climbing.

The deletion of No Name Stack from Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of the bwlch of No Name Stack

LIDAR image of the summit of No Name Stack

The 2m DSM LIDAR analysis gives the hill the following details:

Name:  No Name Stack

Summit Height:  31.1m

Summit Grid Reference:  SR 97567 93273

Bwlch Height:  2.6m

Bwlch Grid Reference:  SR 97553 93308

Drop:  28.5m

Dominance:  not applicable as under 30m prominence

Therefore, the 31.1m LIDAR analysis for the summit position at SR 97567 93273 and the 2.6m LIDAR analysis for the bwlch position at SR 97553 93308 gives this hill 28.5m of drop, which is insufficient for Dominant status.

LIDAR image of No Name Stack

The full details for the hill are:

Group:  Brandy Hill

Name:  No Name Stack

Dominance:  not applicable as under 30m prominence

OS 1:50,000 map:  158

Summit Grid Reference:  SR 97567 93273 (LIDAR)

Summit Height:  31.1m (LIDAR)

Bwlch Grid Reference:  SR 97553 93308 (LIDAR)

Drop Summit to Bwlch:  28.5m (LIDAR)

Drop Bwlch to ODN:  2.6m (LIDAR)

Myrddyn Phillips (September 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Ynys Deullyn (SM 844 340) – Dominant addition (44th reclassification)

Significant Height Revisions post for Ynys Deullyn

There has been confirmation of an addition to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

This hill did not appear in the main P30 list or the accompanying Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website, as it was thought not to have 30m of drop and therefore was not considered for Dominant status.

This hill was included as a P30 and a Dominant hill shortly after the Ordnance Survey Interactive Coverage Map became available on the Geograph website, and prior to LIDAR analysis it was listed with 30m of drop based on the 30m summit spot height that appears on this map.

2m DTM LIDAR image of Ynys Deullyn (SM 844 340)

The name of the hill is Ynys Deullyn and as its name implies it is an island, or more strictly speaking a tidal island that is attached to mainland Wales at low tide.  The hill is adjoined to the Carn Llidi group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), with the island being positioned on the northern part of the Pembrokeshire coast, and has the small community of Abercastell towards its west south-west.

If wanting to visit the island permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so caution is advised as the easiest approach will probably necessitate some form of scramble.

The confirmation of the addition of Ynys Deullyn to Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 2m DSM LIDAR analysis gives the hill the following details:

Name:  Ynys Deullyn

Summit Height:  32.6m

Summit Grid Reference:  SM 84479 34095

Bwlch Height:  2.1m

Bwlch Grid Reference:  SM 84513 34087

Drop:  30.5m

Dominance:  93.51%

2m DSM LIDAR image of Ynys Deullyn (SM 844 340)

Therefore, the 32.6m LIDAR analysis for the summit position at SM 84479 34095 and the 2.1m LIDAR analysis for the bwlch position at SM 84513 34087 gives this hill 30.5m of drop and 93.51% dominance, which is sufficient for Dominant status.

The full details for the hill are:

Group:  Carn Llidi

Name:  Ynys Deullyn

Dominance:  93.51% (LIDAR)

OS 1:50,000 map:  157

Summit Grid Reference:  SM 84479 34095 (LIDAR)

Summit Height:  32.6m (LIDAR)

Bwlch Grid Reference:  SM 84513 34087 (LIDAR)

Drop Summit to Bwlch:  30.5m (LIDAR)

Drop Bwlch to ODN:  2.1m (LIDAR)

Myrddyn Phillips (September 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Gewni (SM 796 236) – Dominant addition (43rd reclassification)

There has been confirmation of an addition to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

This hill did not appear in the main P30 list or the accompanying Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website, as it was thought not to have 30m of drop and therefore was not considered for Dominant status.

Gewni (SM 796 236)

This hill was included as a P30 and a Dominant hill shortly after the Ordnance Survey Interactive Coverage Map became available on the Geograph website, and prior to LIDAR analysis it was listed with 35m of drop based on the 35m summit spot height that appears on this map.

The name of the hill is Gewni and it is a tidal island that is attached to mainland Wales at low tide.  The hill is adjoined to the Carn Llidi group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), with the island being positioned to the west of where the Afon Solfach (River Solva) enters the sea, and has the village of Solfach (Solva) towards its north-east.

If wanting to visit the hill it is a part of designated open access land, for those wishing to do so caution is advised as the easiest approach will probably necessitate some form of scramble.

The confirmation of the addition of Gewni to Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 1m DTM LIDAR analysis gives the hill the following details:

Name:  Gewni

Summit Height:  35.7m

Summit Grid Reference:  SM 79696 23606

Bwlch Height:  0.3m

Bwlch Grid Reference:  SM 79689 23698

Drop:  35.3m

Dominance:  99.11%

LIDAR image of Gewni

Therefore, the 35.65m LIDAR analysis for the summit position at SM 79696 23606 and the 0.3m LIDAR analysis for the bwlch position at SM 79689 23698 gives this hill 35.3m of drop and 99.11% dominance, which is sufficient for Dominant status.

The full details for the hill are:

Group:  Carn Llidi

Name:  Gewni

Dominance:  99.11% (LIDAR)

OS 1:50,000 map:  157

Summit Grid Reference:  SM 79696 23606 (LIDAR)

Summit Height:  35.7m (LIDAR)

Bwlch Grid Reference:  SM 79689 23698 (LIDAR)

Drop Summit to Bwlch:  35.3m (LIDAR)

Drop Bwlch to ODN:  0.3m (LIDAR)

Myrddyn Phillips (August 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pen Twmp (SM 988 329) – Lesser Dominant reclassified to Dominant (42nd reclassification)

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With an accompanying sub list entitled Y Trechol - The Lesser Dominant Hills of Wales, with the criteria for this sub category being those additional Welsh P30 hills whose prominence is 33% or more and below 50% of their absolute height.

This hill was initially listed as a Dominant hill based on interpolation of bwlch contours and later reclassified to Lesser Dominant status based on the 109m spot height that appears on the area of this hill’s bwlch on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

A locally known name of the hill is Pen Twmp and it is adjoined to the Mynydd Preseli group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4).  The hill is positioned with the A 40 road to its west and the B 4313 road to its north and has the Nant y Bugail to its south-west and the River Aer to its north-north-east, and has the town of Abergwaun (Fishguard) towards the north-west.

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so a public footpath passes to the west of the summit and can be accessed from either the north or south-west.

The reclassification of Pen Twmp to Dominant status is due to LIDAR bwlch analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

The 2m DTM LIDAR analysis gives the hill the following details:

Name:  Pen Twmp

Summit Height:  217m

Summit Grid Reference:  SM 98820 32984

Bwlch Height:  108.3m

Bwlch Grid Reference:  SM 99284 32968

Drop:  109m

Dominance:  50.09%

LIDAR image of Pen Twmp

LIDAR image of the bwlch of Pen Twmp

Therefore, the 217m summit spot height and the 108.3m LIDAR analysis for the bwlch position at SM 99284 32968 gives this hill 109m of drop and 50.09% Dominance, which is sufficient for it to be reclassified to a Dominant hill.

The full details for the hill are:

Group:  Mynydd Preseli

Name:  Pen Twmp

Dominance:  50.09%

OS 1:50,000 map:  157

Summit Grid Reference:  SM 98820 32984

Summit Height:  217m

Drop Summit to Bwlch:  109m

Drop Bwlch to ODN:  108.3m

Myrddyn Phillips (August 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pen Twmp (SM 988 329) – Dominant reclassified to Lesser Dominant (41st reclassification)

THIS HILL HAS SUBSEQUENTLY BEEN RECLASSIFIED BACK TO DOMINANT STATUS

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales due to data on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.  This reclassification is retrospective as it was initiated when data on this mapping was first analysed.

The criteria for this list are:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With an accompanying sub list entitled Y Trechol - The Lesser Dominant Hills of Wales, with the criteria for this sub category being those additional Welsh P30 hills whose prominence is 33% or more and below 50% of their absolute height.

During 2006 and 2007 drop values were added to the Welsh P30 lists that had been published on Geoff Crowder’s v-g.me website, this hill was then listed with an estimated c 110m of drop based on the 217m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 107m based on interpolation of bwlch contouring between 105m – 110m, with these values giving this hill 50.69% Dominance, and it was listed as such when this section of the Dominant list was completed in late January / early February 2012.

Extract from the Ordnance Survey 1:25,000 Explorer map

A locally known name of the hill is Pen Twmp and it is adjoined to the Mynydd Preseli group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4).  The hill is positioned with the A 40 road to its west and the B 4313 road to its north and has the Nant y Bugail to its south-west and the River Aer to its north-north-east, and has the town of Abergwaun (Fishguard) towards the north-west.

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so a public footpath passes to the west of the summit and can be accessed from either the north or south-west.

Shortly after Pen Twmp was first listed as a Dominant hill I was informed on how to access what is now known as the Ordnance Survey Interactive Coverage Map that is hosted on the Geograph website.  The larger scale interactive map on this website gives many spot heights that are not shown on other publicly available mapping, and when the details for this hill were analysed this map shows a 109m spot height on the area of this hill’s bwlch, and when coupled with the 217m summit spot height, these values gave the hill 108m of drop and 49.77% Dominance and it was therefore reclassified from a Dominant to a Lesser Dominant hill.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

The full details for the hill are:

Group:  Mynydd Preseli

Name:  Pen Twmp

Dominance:  49.77%

OS 1:50,000 map:  157

Summit Grid Reference:  SM 988 329

Summit Height:  217m

Drop Summit to Bwlch:  108m

Drop Bwlch to ODN:  109m

Myrddyn Phillips (August 2018)






Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Ynys Ddu (SM 886 388) – Dominant addition (40th reclassification)

There has been confirmation of an addition to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

This hill did not appear in the main P30 list or the accompanying Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website, as it was thought not to have 30m of drop and therefore was not considered for Dominant status.

Ynys Ddu (SM 886 388).  Photo: Jon Glew

It was Mick Moore who brought the attention of this hill’s P30 status to the hill bagging community and prior to LIDAR analysis the hill was listed with an estimated summit height of c 32m based on a small 30m uppermost contour ring on Ordnance Survey 1:25,000 Explorer maps.

The name of the hill is Ynys Ddu and as its name implies it is an island, or more strictly speaking a tidal island that is attached to mainland Wales at low tide.  The hill is adjoined to the Mynydd Preseli group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), with the island being positioned on the western part of Pen-caer (Stumble Head), and has the town of Abergwaun (Fishguard) towards the east south-east.

The summit of Ynys Ddu.  Photo: Jon Glew

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so caution is advised as the easiest approach will probably necessitate a scramble.

The confirmation of the addition of Ynys Ddu to Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 2m DSM LIDAR analysis gives the hill the following details:

Ynys Ddu

Summit Height:  31.9m

Summit Grid Reference:  SM 88673 38869

Bwlch Height:  0.5m

Bwlch Grid Reference:  SM 88721 38853

Drop:  31.3m

Dominance:  98.28% 

LIDAR image of Ynys Ddu

Therefore, the 31.9m LIDAR analysis for the summit position at SM 88673 38869 and the 0.5m LIDAR analysis for the bwlch position at SM 88721 38853 gives this hill 31.3m of drop and 98.28% Dominance, which is sufficient for Dominant status.

The full details for the hill are:

Group:  Mynydd Preseli

Name:  Ynys Ddu

Dominance:  98.28%

OS 1:50,000 map:  157

Summit Grid Reference:  SM 88673 38869 (LIDAR)

Summit Height:  31.9m (LIDAR)

Drop Summit to Bwlch:  31.3m (LIDAR)

Drop Bwlch to ODN:  0.5m (LIDAR)

My thanks to Jon Glew for permission to reproduce his photos of Ynys Ddu

Myrddyn Phillips (July 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Fegla Fach (SH 638 153) – Dominant addition (39th reclassification)

Survey post for Fegla Fach

Significant Height Revisions post for Fegla Fach

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis, an on-site visit and a survey with the Trimble GeoXH 6000 which took place on the 17^th May 2018, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

This hill did not appear in the accompanying Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria for this sub category; however this sub list has now been standardised including the addition of interpolated drop values and heights.

Prior to LIDAR analysis, an on-site visit and the Trimble GeoXH 6000 survey this hill was listed with 25m of drop based on the 28m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 3m spot height that appears on the area of this hill’s bwlch on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

The name of the hill is Fegla Fach and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), with the hill being positioned between the Afon Mawddach to its west and north and the A 493 road to its south-east, and has the village of Y Friog (Fairbourne) to the south-west.  

Fegla Fach from across the Afon Mawddach

Fegla Fach from its connecting bwlch

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so the minor road to the south of the hill joins a public footpath that then heads toward it.

The addition of Fegla Fach to Dominant status is in part due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 1m DTM LIDAR analysis gives the hill the following details:

Fegla Fach

Summit Height:  31.5m

Summit Grid Reference:  SH 63818 15311

Bwlch Height:  1.6m

Bwlch Grid Reference:  SH 63691 15131 and SH 69693 15130

Drop:  29.9m

This hill and others in the vicinity used to be tidal islands before sea defences were constructed, with the Afon Mawddach positioned to the immediate north, west and east of the hill, this has resulted in this hill now being landlocked by its connecting bwlch which is a part of the larger Arthog Bog. 

The area of the connecting bwlch of this hill is complicated to analyse via LIDAR as it is low lying and the land has been terraformed with embankments and drainage ditches.  However, extensive LIDAR analysis pinpoints the position of what can be construed as this hill’s remaining natural bwlch to be on or just below what is now a small land bridge.

LIDAR image of Fegla Fach (top right corner) and the land making up the Arthog Bog

This land bridge crosses one of many drainage ditches in the Arthog Bog and this position was surveyed using the Trimble GeoXH 6000, with three measurement offsets noted, the first to ground making up the land bridge, the second to water level in the drainage ditch and the third to ground mid-way between the land bridge and the water level, the survey results appear below:

1^st survey, land bridge:  1.577m

2^nd survey, water level in drainage ditch:  1.337m

3^rd survey, mid-point between land bridge and water level:  1.457m

The Trimble GeoXH 6000 gathering data at the bwlch of Fegla Fach

When these survey results are combined with the LIDAR result for the summit of this hill the drop values for each of the three points at the bwlch are:

1^st survey, land bridge:  29.912m

2^nd survey, water level in drainage ditch:  30.152m

3^rd survey, mid-point between land bridge and water level:  30.032m

The summit of this hill was analysed using the 1m DTM LIDAR model and as the high point consists of a large rock with a number of trees growing directly beside it, it is probable that the LIDAR technique did not model the very highest part of this rock, and when coupled with the result produced by the Trimble bwlch survey it is deemed sufficient to list this hill with a drop value of 30m, which when coupled with the summit height produced by LIDAR analysis gives this hill 95.37% Dominance.

The summit of Fegla Fach

The full details for the hill are:

Group:  Cadair Idris

Name:  Fegla Fach

Dominance:  95.37%

OS 1:50,000 map:  124

Summit Grid Reference:  SH 63818 15311 (LIDAR)

Summit Height:  31.5m (LIDAR)

Drop Summit to Bwlch:  30.0m (LIDAR summit and Trimble bwlch)

Drop Bwlch to ODN:  1.5m (LIDAR summit and Trimble bwlch)

For details on the survey of Fegla Fach

Myrddyn Phillips (July 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Rhos Ymryson (SN 460 500) – Dominant reclassified to Lesser Dominant (38th reclassification)

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales initiated by re-evaluation of the summit height of the hill and subsequent LIDAR bwlch analysis, resulting in this hill being reclassified to the Lesser Dominant list. 

The criteria for this listing are:

Y Trechol – The Dominant Hills of Wales - Welsh P30s whose prominence equal or exceed half that of their absolute height, with the criteria for Lesser Dominant status being those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

Prior to this re-evaluation it was listed as a Dominant hill based on the 327m summit spot height  and the 163m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map, these values gave this hill 164m of drop and 50.15% Dominance.  Importantly the 327m summit spot height is given to the top of a covered reservoir; these constructions are not included in the criterion for summit height within this list, with ground at the immediate base of such constructions considered natural ground and therefore the point at which the height of the summit should be taken.  The ten figure grid reference reported for the highest remaining natural ground of this hill is at SN 46038 50017, this is extremely close to where a 1062ft (323.7m) levelled height appears on the Ordnance Survey 1906 Six-Inch map which matches the 324m rounded up height on the Ordnance Survey 1:50,000 Landranger map, and it is this height that is being taken as that for the highest remaining natural ground of this hill.

However, it was not until LIDAR became available that the bwlch details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

The name of the hill is Rhos Ymryson and it is the highest point in its own group of hills which are situated in Mid and West Wales (Region B, Sub-Region B3).  The hill overlooks the B 4338 road which is to its north, with the small community of Talgarreg to its west north-west and Mydroilyn towards its north.

As the summit of the hill is not on designated open access land permission to visit should be sought, for those wishing to do so an access track to the covered reservoir leaves the convenience of the B 4338 road to the north of the summit with a public footpath leaving this same road to the west of the access track.

The reclassification of Rhos Ymryson from Dominant to Lesser Dominant hill is due to the re-evaluation of its summit height and as the 327m spot height that appears on the Ordnance Survey 1:25,000 Explorer map is given to the top of a covered reservoir, it is the old levelled height on the Ordnance Survey Six-Inch map which matches the rounded up 324m height on the Ordnance Survey 1:50,000 Landranger map that is being taken as the summit height of this hill, and when coupled with the 162.5m bwlch height derived from LIDAR analysis, these values give this hill 161m of drop and 49.83% dominance, which is insufficient for it to be classified as a Dominant hill.

The full details for the hill are:

Group:  Rhos Ymryson

Name:  Rhos Ymryson

Dominance:  49.83%

OS 1:50,000 map:  146

Summit Grid Reference:  SN 46038 50017

Summit Height:  324m

Drop Summit to Bwlch:  161m

Drop Bwlch to ODN:  162.5m 

Myrddyn Phillips (June 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pt. 70.3m (SH 309 297) – Lesser Dominant deletion (37th reclassification)

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales due to analysis of data produced by LIDAR and which was initially conducted by Chris Crocker, and subsequently by Myrddyn Phillips, with the details relating to this hill taken from the latter’s analysis.

The criteria for inclusion to the Dominant list are all Welsh P30 hills whose prominence equal or exceed half that of their absolute height, whilst the criteria for the Lesser Dominant list are those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

Prior to analysis of data produced via LIDAR this hill was listed with 42.25% Dominance based on an estimated summit height of c 71 and the 41m bwlch spot height that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, with these values giving this hill c 30m of drop.

As the author does not know a local or historical name for this hill it is being listed by the point (Pt. 70.3m) notation, and it is positioned in the Pen Llŷn group and placed in the North Wales region (Region A, Sub-Region A1), and is situated between the small communities of Llanbedrog to the north-east, Mynytho to the north-west and Abersoch to the south.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of designated open access land, however the hill has a number of public footpaths encircling it that start from the A 499 road to its east and the network of minor roads to its north and west.

The deletion of Pt. 70.3m from Lesser Dominant status is due to analysis of data produced by LIDAR initially conducted by Chris Crocker, and subsequently by Myrddyn Phillips, with the details from the latter’s analysis being presented below.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The analysis of data produced via LIDAR gives the hill the following details:

Pt. 70.3m

Summit Height:  70.3m

Summit Grid Reference:  SH 30993 29739

Bwlch Height:  40.7m

Bwlch Grid Reference:  SH 31021 30355

Drop:  29.6m

Dominance:  not applicable

Therefore, the 70.267m data produced via LIDAR for the summit position at SH 30993 29739 and the 40.710m data produced via LIDAR for the bwlch position at SH 31021 30355 gives this hill 29.557m of drop, with the drop value insufficient for qualification to the Dominant list.

The full details for the hill are:

Group:  Pen Llŷn

Name:  Pt. 70.3m

Dominance:  not applicable

OS 1:50,000 map:  123

Summit Grid Reference:  SH 30993 29739 

Summit Height:  70.3m (data via LIDAR)

Drop Summit to Bwlch:  29.6m (data via LIDAR)

Drop Bwlch to ODN:  40.7m (data via LIDAR)

My thanks to Chris Crocker for initial LIDAR analysis and bringing the details of this hill to my attention

Myrddyn Phillips (April 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Coed y Garth (SH 660 165) – Lesser Dominant deletion (36th reclassification)

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales due to analysis of data produced by LIDAR and which was initially conducted by Chris Crocker and George Gradwell, and subsequently by Myrddyn Phillips, with the details relating to this hill taken from the latter’s analysis.

The criteria for inclusion to the Dominant list are all Welsh P30 hills whose prominence equal or exceed half that of their absolute height, whilst the criteria for the Lesser Dominant list are those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

Prior to analysis of data produced via LIDAR this hill was listed with 35.63% Dominance based on the 87m summit spot height that appears on the Harvey 1:25,000 Cadair Idris Superwalker map and the 56m bwlch spot height on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, with these values giving this hill 31m of drop.

The name of the hill is Coed y Garth and it is positioned in the Cadair Idris group and is placed in the North Wales Region (Region A, Sub-Region A3), and is situated between the small communities of Arthog to the south-west and Abergwynant to the east north-east.

As the hill is situated in conifer plantation a route to its summit may prove problematic, for those wishing to visit access from the track that crosses its bwlch to the north-east may offer the quickest approach.

The deletion of Coed y Garth from Lesser Dominant status is due to analysis of data produced by LIDAR initially conducted by Chris Crocker and George Gradwell, and subsequently by Myrddyn Phillips, with the details from the latter’s analysis being presented below.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The analysis of data produced via LIDAR gives the hill the following details:

Coed y Garth

Summit Height:  83.4m

Summit Grid Reference:  SH 66061 16545

Bwlch Height:  56.2m

Bwlch Grid Reference:  SH 66291 16811

Drop:  27.1m

Dominance:  not applicable

Therefore, the 83.372m data produced via LIDAR for the summit position at SH 66061 16545 and the 56.238m data produced via LIDAR for the bwlch position at SH 66291 16811 gives this hill 27.134m of drop, with the drop value insufficient for qualification to the Dominant list.

The full details for the hill are:

Group:  Cadair Idris

Name:  Coed y Garth

Dominance:  not applicable

OS 1:50,000 map:  124

Summit Grid Reference:  SH 66061 16545 

Summit Height:  83.4m (data via LIDAR)

Drop Summit to Bwlch:  27.1m (data via LIDAR)

Drop Bwlch to ODN:  56.2m (data via LIDAR)

My thanks to Chris Crocker and George Gradwell for initial LIDAR analysis and bringing the details of this hill to my attention

Myrddyn Phillips (April 2018)