Wednesday, 6 November 2019

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau


30-99m Twmpau – Hill Reclassifications

The 30-99m Twmpau (thirty welsh metre prominences and upward) are the Welsh hills at or above 30m and below 100m in height that have a minimum drop of 30m.  Accompanying the main P30 list are two sub lists entitled the 30-99m Sub-Twmpau with the qualification to this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, and the Double Sub-Twmpau with the qualification to this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop.

The list is authored by Myrddyn Phillips and the posts that have appeared on Mapping Mountains detailing the additions, reclassifications and deletions to the main P30 list and the sub lists appear below presented chronologically in receding order.








Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

The Knoll (ST 424 904) – 30-99m Twmpau reclassified to 100m Twmpau (53rd reclassification)


There has been a reclassification to the list of 30-99m Twmpau and 100m Twmpau, 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 The Knoll (ST 424 904)

The criteria for the two listings that this reclassification applies to are:

30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The name the hill is listed by is The Knoll, and it is adjoined to the Gwent Is Coed group of hills which are situated in the south-eastern part of South Wales (Region C, Sub-Region C3), and it is positioned with the A48 road to its north and the M4 motorway to its south, and has the city of Casnewydd (Newport) towards the west south-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 main P30 list and listed with a c 90m summit height, based on its uppermost contour that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

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

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with c 51m of drop, based on an estimated c 94m summit height based on interpolation of 5m contouring and a 43m bwlch spot height that appears on 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 close-up image of The Knoll

Therefore, the reclassification of this hill from 30-99m Twmpau to 100m Twmpau status is due to LIDAR analysis, resulting in a 101.9m summit height and a 43.1m bwlch height, with these values giving this hill 58.7m of drop and 57.66% dominance.  With the summit height of this hill sufficient for it now to be classified as a 100m Twmpau.


The full details for the hill are:

Group:  Gwent Is Coed

Name:  The Knoll

OS 1:50,000 map:  171, 172

Summit Height:  101.9m (LIDAR)

Summit Grid Reference:  ST 42467 90424 (LIDAR)

Bwlch Height:  43.1m (LIDAR)

Bwlch Grid Reference:  ST 42135 90345 (LIDAR)

Drop:  58.7m (LIDAR)


Myrddyn Phillips (July 2020)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Long Park (SS 072 984) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (52nd reclassification)



There has been a reclassification of a hill in the listing of the 30-99m Twmpau, 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 Long Park (SS 072 984)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The name the hill is listed by is Long Park and this was derived from the Tithe map and it 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 south, the A4139 road to its north and the B4585 road to its west and south, and has the village of Maenorbŷr (Manorbier) towards the south-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 was considered not to meet the criteria then used in the main P30 category. 

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 an estimated c 80m summit height and an estimated bwlch height of c 51m, with both heights based on interpolation of 5m contouring that appears on Ordnance Survey 1:25,000 Explorer maps.

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 had many spot heights not on other publicly available Ordnance Survey maps.  As no additional information was shown on this mapping, the details for the hill 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 for Long Park

The reclassification of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 79.2m summit height and a 48.0m bwlch height, with these values giving this hill 31.1m of drop which is sufficient for 30-99m Twmpau status.  With the 48.0m bwlch height taken to a railway cutting which meets the criteria used in this list.


The full details for the hill are:

Group:  Brandy Hill

Name:  Long Park

OS 1:50,000 map:  158

Summit Height:  79.2m (LIDAR)

Summit Grid Reference:  SS 07255 98449 (LIDAR)

Bwlch Height:  48.0m (LIDAR)

Bwlch Grid Reference:  SS 06985 99391 (LIDAR)

Drop:  31.1m (LIDAR)


Myrddyn Phillips (May 2020)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Caerau (ST 134 748) – 30-99m Sub-Twmpau addition (51st reclassification)



There has been an addition of a hill to the listing of the 30-99m Twmpau, 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 Caerau (ST 134 748)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The name the hill is listed by is Caerau 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 A48 road to its north-west and the A4232 road to its immediate south and east, and has the district of Ely in the western fringes of the city of Caerdydd (Cardiff) towards the north.

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 the Hills to be surveyed sub list that accompanied the main P30 list, as it did not meet the criteria then used in this sub category.  

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 28m of drop based on an c 81m interpolated summit height and an estimated bwlch height of c 53m.

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

This reassessment was reliant upon the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.  This mapping has many more spot heights compared to other publicly available Ordnance Survey maps, and the OS Maps website which 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.

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. 

Close up LIDAR image of Caerau

Therefore, the addition of Caerau to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in an 80.9m summit height positioned at ST 13476 74874 and a 51.4m bwlch height positioned at ST 13446 74765, with these values giving this hill 29.5m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau.


The full details for the hill are:

Group:  Bro Morgannwg

Name:  Caerau

OS 1:50,000 map:  171

Summit Height:  80.9m (LIDAR)

Summit Grid Reference:  ST 13476 74874 (LIDAR)

Bwlch Height:  51.4m (LIDAR)

Bwlch Grid Reference:  ST 13446 74765 (LIDAR)

Drop:  29.5m (LIDAR)


Myrddyn Phillips (November 2019)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Dinas Powys (ST 148 722) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (50th reclassification)

Significant Height Revisions post for Dinas Powys



There has been confirmation of a reclassification of a hill to the listing of the 30-99m Twmpau, 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 Dinas Powys (ST 148 722)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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 more spot heights compared to 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 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 confirmation of the reclassification of Dinas Powys to 30-99m Twmpau 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, which is sufficient for this hill to be classified as a 30-99m Twmpau.


The full details for the hill are:

Group:  Bro Morgannwg

Name:  Dinas Powys

OS 1:50,000 map:  171

Summit Height:  69.4m (LIDAR)

Summit Grid Reference:  ST 14823 72225 (LIDAR)

Bwlch Height:  33.6m (LIDAR)

Bwlch Grid Reference:  ST 14757 72333 (LIDAR)

Drop:  35.8m (LIDAR)


Myrddyn Phillips (November 2019)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ynys y Barri (ST 120 668) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (49th reclassification)



There has been confirmation of a reclassification of a hill to the listing of the 30-99m Twmpau, 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 Ynys y Barri (ST 120 668)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The name the hill is listed by is Ynys y Barri 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 as its name implies it is an island, which is now joined to the mainland by the A4055 road, and has the town of Y Barri (Barry) to its immediate north.

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. 

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

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 36m of drop based on the 42m summit height derived from information received from David Purchase relating to a height on the Ordnance Survey series of 1:10,000 maps and an estimated bwlch height of c 6m.

Extract from the Ordnance Survey series of 1:10,000 maps

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.  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 the reclassification of Barry Island to 30-99m Twmpau status is due to LIDAR analysis, resulting in a 41.6m summit height and a 2.9m bwlch height, with these values giving this hill 38.7m of drop, which is sufficient for this hill to be classified as a 30-99m Twmpau.


The full details for the hill are:

Group:  Bro Morgannwg

Name:  Ynys y Barri

OS 1:50,000 map:  171

Summit Height:  41.6m (LIDAR)

Summit Grid Reference:  ST 12019 66818 (LIDAR)

Bwlch Height:  2.9m (LIDAR)

Bwlch Grid Reference:  ST 10943 66794 (LIDAR)

Drop:  38.7m (LIDAR)


Myrddyn Phillips (November 2019)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ash Tip (ST 031 663) – 30-99m Twmpau addition (48th reclassification)

Significant Name Changes post for Ash Tip

Significant Height Revisions post for Ash Tip



There has been an addition of a hill to the listing of the 30-99m Twmpau, 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 Ash Tip (ST 031 663)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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 30-99m Twmpau 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, which is sufficient for this hill to be classified as a 30-99m Twmpau.


The full details for the hill are:

Group:  Bro Morgannwg

Name:  Ash Tip

OS 1:50,000 map:  170

Summit Height:  50.0m (LIDAR)

Summit Grid Reference:  ST 03170 66338 (LIDAR)

Bwlch Height:  12.4m (LIDAR)

Bwlch Grid Reference:  ST 03298 66735 (LIDAR)

Drop:  37.6m (LIDAR)


Myrddyn Phillips (October 2019)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Deg Erw Llandafin (ST 003 731) – 30-99m Twmpau reclassified to 30-99m Sub-Twmpau (47th reclassification)

Significant Name Changes post for Deg Erw Llandafin



There has been confirmation of a reclassification to a hill listed in the 30-99m Twmpau, 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 Deg Erw Llandafen (ST 003 731)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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.

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 became available online; 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 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 confirmation of the reclassification of this hill to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 66.4m summit height and a 37.2m bwlch height, with these values giving this hill 29.2m of drop, which is insufficient for continued 30-99m Twmpau status. 


The full details for the hill are:

Group:  Bro Morgannwg

Name:  Deg Erw Llandafin

OS 1:50,000 map:  170

Summit Height:  66.4m (LIDAR)

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

Bwlch Height:  37.2m (LIDAR)

Bwlch Grid Reference:  ST 00721 73222 (LIDAR)

Drop:  29.2m (LIDAR)


Myrddyn Phillips (October 2019)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 65.9m (ST 352 947) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (46th reclassification)



There has been confirmation of a reclassification to a hill listed in the 30-99m Twmpau, 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:

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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 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 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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; 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. 

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 the reclassification of this hill to 30-99m Twmpau 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, which is sufficient for 30-99m Twmpau status. 


The full details for the hill are:

Group:  Cymoedd Gwent

Name:  Pt. 65.9m

OS 1:50,000 map:  171

Summit Height:  65.9m (LIDAR)

Summit Grid Reference:  ST 35225 94717 (LIDAR)

Bwlch Height:  34.3m (LIDAR)

Bwlch Grid Reference:  ST 35297 94949 (LIDAR)

Drop:  31.6m (LIDAR)


Myrddyn Phillips (September 2019)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 77.7m (ST 129 775) – 30-99m Twmpau addition (45th reclassification)



There has been an addition to the list of 30-99m Twmpau, 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. 77.7m (ST 129 775)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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 30-99m Twmpau 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. 

The inclusion of this hill to 30-99m Twmpau 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 Height:  77.7m (LIDAR)

Summit Grid Reference:  ST 12931 77574 (LIDAR)

Bwlch Height:  44.4m (LIDAR)

Bwlch Grid Reference:  ST 11808 79174 (LIDAR)

Drop:  33.3m (LIDAR)


Myrddyn Phillips (August 2019)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ynys Fach (SM 707 237) – Double Sub-Twmpau addition (44th reclassification)


There has been an addition to the list of 30-99m Twmpau, with the summit height and its location, the drop and status of the hill confirmed by LIDAR analysis conducted by Aled Williams.

Ynys Fach (SM 707 237)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, this height band of hills has two accompanying sub lists, the first of which is entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, and the second sub category is entitled the Double Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The name of the hill is Ynys Fach, and as its name implies it is an island, and it 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), and is positioned adjacent to the central eastern coastline of Ynys Dewi.

This hill did not appear in 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 did not meet the criteria then used for this sub category, however this sub list has now been standardised, with interpolated drop values and interpolated summit heights also included.

It was not until LIDAR became available that the details for this hill could be accurately 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 Ynys Fach (SM 707 237); 1m contour (black), 10m contour (red) and sea level (yellow)

The addition of this hill to Double Sub-Twmpau status is due to LIDAR analysis conducted by Aled Williams, resulting in a 25.7m summit height and with its bwlch at sea level this is also the drop value for the hill, which is sufficient for it to be classified as a Double Sub-Twmpau.


The full details for the hill are:

Group:  Carn Llidi

Name:  Ynys Fach

OS 1:50,000 map:  157

Summit Height:  25.7m (LIDAR)

Summit Grid Reference:  SM 70712 23702 (LIDAR)

Bwlch Height:  N/A, sea level

Bwlch Grid Reference:  N/A, sea level

Drop:  25.7m (LIDAR)


My thanks to Aled Williams for forwarding his LIDAR analysis of this hill

Myrddyn Phillips (July 2019)


© Crown: CHERISH PROJECT 2019. Produced with EU funds through the Ireland Wales Co-operation Programme 2014-2020. All material made freely available through the Open Government Licence.







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 23.8m (SM 706 236) – Double Sub-Twmpau deletion (43rd reclassification)


There has been a deletion to the list of 30-99m Twmpau, with the summit height and its position determined by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips which took place on the 15th May 2016, and subsequent LIDAR analysis for summit and bwlch height and the status of the hill conducted by Aled Williams.

Pt. 23.8m (SM 706 236)


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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, this height band of hills has two accompanying sub lists, the first of which is entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, and the second sub category which this hill has been deleted from is entitled the Double Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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. 23.8m) notation, and it 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), and it is positioned in the central eastern part of Ynys Dewi.

This hill did not appear in 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 did not meet the criteria then used for this sub category, however this sub list has now been standardised, with interpolated drop values and interpolated summit heights also included.

The summit of this hill was subsequently surveyed with the Trimble GeoXH 6000 resulting in a 23.8m summit height, and with an estimated bwlch height of c 2m it was included as a Double Sub-Twmpau with c 22m of drop.

The Trimble GeoXH 6000 gathering data at the summit of Pt. 23.8m (SM 706 236)


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 Pt. 23.8m (SM 706 236).  1m contour (black), 10m contour (red) and sea level (yellow)

The deletion of this hill from Double Sub-Twmpau status is due to LIDAR analysis conducted by Aled Williams, resulting in a 23.8m summit height and a 5m bwlch height based on LIDAR contouring, with these values giving this hill 18.8m of drop which is insufficient for it to retain its Double Sub-Twmpau status.


The full details for the hill are:

Group:  Carn Llidi

Name:  Pt. 23.8m

OS 1:50,000 map:  157

Summit Height:  23.8m (converted to OSGM15)

Summit Grid Reference:  SM 70677 23686

Bwlch Height:  5.0m (based on LIDAR contouring)

Bwlch Grid Reference:  SM 70634 23719 (based on LIDAR contouring) 
  
Drop:  18.8m (Trimble summit and LIDAR summit and bwlch)



My thanks to Aled Williams for forwarding his LIDAR analysis of this hill



Myrddyn Phillips (July 2019)


© Crown: CHERISH PROJECT 2019. Produced with EU funds through the Ireland Wales Co-operation Programme 2014-2020. All material made freely available through the Open Government Licence.







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Redding (ST 087 776) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (42nd reclassification)

Significant Name Changes post for Redding



There has been confirmation of a reclassification to the list of 30-99m Twmpau, 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 Redding

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The name of the bounded land where the summit of this hill is situated is Redding, and this was derived from the Tithe map and it is this name that the hill is now being listed by.  The hill 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 has the M4 towards its north-west and the A4232 road to its east, and has the city of Caerdydd (Cardiff) towards its east.

This hill was included in 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 did not meet the criteria then used for the main P30 list.  The sub list has now been standardised and interpolated drop values and interpolated summit heights have also been included in the main P30 and sub list.

When interpolated heights were used in this list this hill was listed with an estimated c 30m of drop, based on the 81m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 51m based on interpolation of bwlch contouring between 50m – 55m.

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 became available online; this mapping is entitled the Interactive Coverage Map, and its larger scale enabled a better assessment of bwlch contouring, this resulted in the same estimated c 51m bwlch height giving this hill the same estimated drop value of c 30m.

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 reclassification to 30-99m Twmpau status is due to LIDAR analysis, resulting in an 80.3m summit height and a 49.05m bwlch height, with these values giving this hill 31.3m of drop.


The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Redding

OS 1:50,000 map:  170

Summit Height:  80.3m (LIDAR, natural summit)

Summit Grid Reference:  ST 08782 77683 (LIDAR, natural summit)

Bwlch Height:  49.05m (LIDAR)

Bwlch Grid Reference:  ST 08551 79827 (LIDAR)

Drop:  31.3m (LIDAR)


Myrddyn Phillips (June 2019)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 85.8m (SS 748 953) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (41st reclassification)



There has been confirmation of a reclassification to the list of 30-99m Twmpau, 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. 85.8m (SS 748 953)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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. 85.8m) 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 has the A474 road to its west and the B4287 road to its north-east, and has the town of Castell-nedd (Neath) towards its north.

This hill was included in 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 did not meet the criteria then used for the main P30 list, however interpolated drop values and interpolated summit heights have now been included and the sub list has also been standardised.

When interpolated heights were used in this list this hill was listed with an estimated c 33m of drop, based on an estimated summit height of c 85m and an estimated bwlch height of c 52m, with both heights based on interpolation of 10m contouring on the Ordnance Survey 1:25,000 Explorer map.

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 became available online; this mapping is entitled the Interactive Coverage Map, and its larger scale and use of 5m contour intervals enabled a better judgement for the drop value of this hill and it was subsequently listed with an estimated c 34m of drop.

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 reclassification to 30-99m Twmpau status is due to LIDAR analysis, resulting in an 85.8m summit height and a 53.4m bwlch height, with these values giving this hill 32.4m of drop.


The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Pt. 85.8m

OS 1:50,000 map:  170

Summit Height:  85.8m (LIDAR)

Summit Grid Reference:  SS 74860 95395 (LIDAR)

Bwlch Height:  53.4m (LIDAR)

Bwlch Grid Reference:  SS 74976 95453 (LIDAR)

Drop:  32.4m (LIDAR)


Myrddyn Phillips (June 2019)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 22.2m (SM 701 226) – Double Sub-Twmpau addition (40th reclassification)

Significant Height Revisions post for Pt. 22.2m


There has been an addition to the list of 30-99m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Aled Williams.

Pt. 22.2m (SM 701 226)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, this height band of hills has two accompanying sub lists, the first of which is entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, and the second sub category which this hill is a part of is entitled the Double Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

As the authors do not know an appropriate name for this hill either from historic research or local enquiry it is being listed by the point (Pt. 22.2m) notation, and it 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), and it is positioned in a small sheltered bay on the southern side of Ynys Dewi.

This hill did not appear in 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 did not meet the criteria then used for this sub category, however this sub list has now been standardised, with interpolated drop values and interpolated summit heights also included.

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

Even when this sub list was standardised contemporary Ordnance Survey 1:25,000 Explorer maps do not give it any contour ring.  The lack of contour rings is also applicable to the Ordnance Survey Vector Map Local hosted on the Geograph website which is entitled the Interactive Coverage Map.

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

The details for this hill were re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has 5m contour intervals.  It was not subsequently included as a Double Sub-Twmpau as this mapping gives this hill an uppermost 15m ring contour.

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.

LIDAR image of Pt. 22.2m; 1m contour (black), 10m contour (red) and sea level (yellow)

Close up LIDAR image of Pt.  22.2m; 1m contour (black), 10m contour (red) and sea level (yellow)

The addition of this hill to Double Sub-Twmpau status is due to LIDAR analysis conducted by Aled Williams, resulting in a 22.2m summit height and as this is also its drop value as the connecting bwlch is below sea level, this confirms its addition to Double Sub-Twmpau status.


The full details for the hill are:

Group:  Carn Llidi

Name:  Pt. 22.2m

OS 1:50,000 map:  157

Summit Height:  22.2m (LIDAR)

Summit Grid Reference:  SM 70180 22696 (LIDAR)

Bwlch Height:  N/A, sea level

Bwlch Grid Reference:  N/A, sea level 
  
Drop:  22.2m (LIDAR)


Myrddyn Phillips (June 2019)


© Crown: CHERISH PROJECT 2019. Produced with EU funds through the Ireland Wales Co-operation Programme 2014-2020. All material made freely available through the Open Government Licence.






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Warren Hill (SS 736 940) – 30-99m Twmpau addition (39th reclassification)



There has been confirmation of an addition to the list of 30-99m Twmpau, with the summit height, its location, 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:

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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.

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. 

LIDAR summit image of Warren Hill

The confirmation of this hill’s addition to 30-99m Twmpau 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.


The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Warren Hill

OS 1:50,000 map:  170

Summit Height:  44.5m (LIDAR)

Summit Grid Reference:  SS 73667 94066 (LIDAR)

Bwlch Height:  13.2m (LIDAR)

Bwlch Grid Reference:  SS 73596 94201 (LIDAR)

Drop:  31.3m (LIDAR)


Myrddyn Phillips (May 2019)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 63.3m (SH 491 760) – 30-99m Twmpau reclassified to 30-99m Sub-Twmpau (38th reclassification)

Survey post for Pt. 63.3m



There has been a reclassification to a hill that is listed in the 30-99m Twmpau, with the bwlch height and its location confirmed by LIDAR analysis, and a subsequent summit survey with the Trimble GeoXH 6000, both conducted by Myrddyn Phillips with the latter taking place on the 22nd October 2018.

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

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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

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 reclassification of Pt. 63.3m to 30-99m Sub-Twmpau 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 30-99m Twmpau 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 Height:  63.3m (converted to OSGM15)

Summit Grid Reference:  SH 49157 76080

Bwlch Height:  35.1m (LIDAR)

Bwlch Grid Reference:  SH 49043 76701 (LIDAR)

Drop:  28.2m (Trimble summit and LIDAR bwlch)



Myrddyn Phillips (April 2019)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Coed Darcy (SS 711 955) – 30-99m Twmpau reclassified to 30-99m Sub-Twmpau (37th reclassification)

Significant Name Changes post for Coed Darcy

Significant Height Revisions post for Coed Darcy



There has been a reclassification to the listing of 30-99m Twmpau, 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:

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The name the hill is now 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.

Extract from the Ordnance Survey 1:25,000 Explorer map from 1998

After this list was standardised and interpolated heights also included this hill was listed with 31m of drop, 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 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 Darcy

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 continued 30-99m Twmpau status.


The full details for the hill are:

Group:  Fforest Fawr

Name:  Coed Darcy

OS 1:50,000 map:  170

Summit Height:  80.4m (LIDAR)

Summit Grid Reference:  SS 71147 95565 (LIDAR)

Bwlch Height:  53.0m (LIDAR)

Bwlch Grid Reference:  SS 71330 95324 (LIDAR)

Drop:  27.4m (LIDAR)


Myrddyn Phillips (April 2019)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cae Doctor (SH 304 399) – 30–99m Sub-Twmpau reclassified to 30-99m Twmpau (36th reclassification)

Survey post for Cae Doctor

Significant Name Changes post for Cae Doctor


There has been confirmation of a Hill Reclassification to the list of 30-99m Twmpau, with the summit height, its location, the drop and status of the hill confirmed by LIDAR analysis, with the bwlch LIDAR analysis initially conducted by Aled Williams, and a subsequent summit survey with the Trimble GeoXH 6000 conducted by Myrddyn Phillips, with the latter taking place on the 3rd October 2018.

The summit of Cae Doctor (SH 304 399)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

When the original Welsh 30-99m height band of 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 with interpolated heights and drop values included this hill was listed with an estimated c 30m of drop based on the 68m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 38m based on interpolation of 10m bwlch contouring.

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

The details for this hill were reassessed when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online, and this map has a 37m spot height positioned at SH 30870 40378 on a minor road on the area of this hill’s bwlch, and if taken as a part of this hill’s drop this would give a value of 31m.

The locally known name for the bounded land where the summit of this hill is situated is Cae Doctor, and this is the name the hill is now listed by.  The hill 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 it has the A497 road to its immediate south-east and the B4417 road to its north-west, and has the small town of Nefyn to the north.

The confirmation of the reclassification of Cae Doctor to 30-99m Twmpau status is due to LIDAR analysis of the bwlch conducted by Aled Williams and a summit survey with the Trimble GeoXH 6000 conducted by Myrddyn Phillips, resulting in a 67.0m summit height and a 35.8m bwlch height, with these values giving this hill 31.2m of drop which is sufficient for it to be classified as a 30-99m Twmpau.

The Trimble GeoXH 6000 gathering data at the summit of Cae Doctor (SH 304 399)


The full details for the hill are:

Group:  Pen Llŷn

Name:  Cae Doctor

OS 1:50,000 map:  123

Summit Height:  67.0m (converted to OSGM15)

Summit Grid Reference:  SH 30425 39978

Bwlch Height:  35.8m (LIDAR)

Bwlch Grid Reference:  SH 30747 40107 (LIDAR)

Drop:  31.2m (Trimble summit and LIDAR bwlch)


My thanks to Aled Williams for initial LIDAR analysis of this hill’s bwlch


Myrddyn Phillips (February 2019)



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