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

Foel Caethle (SN 606 986) – Lesser Dominant addition

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 derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Foel Caethle (SN 606 986)

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 Foel Caethle and it is adjoined to the Tarren y Gesail group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with a minor road to its north and the A493 road to its west and south, and has the town of Tywyn towards the north-west.

After the original 100m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised and interpolated heights and drop values also included, this hill was listed with an estimated c 53m of drop, based on the 169m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 116m bwlch height, based on interpolation of 10m contouring between 110m – 120m, with these values giving this hill 31.36% 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.

Therefore, the addition of this hill to Lesser Dominant status is due to LIDAR analysis, resulting in a 168.8m summit height and a 112.1m bwlch height, with these values giving this hill 56.8m of drop and 33.62% dominance, which is sufficient for Lesser Dominant status. 

 

The full details for the hill are:

Group:  Tarren y Gesail

Name:  Foel Caethle

OS 1:50,000 map:  135

Summit Height:  168.8m (LIDAR)

Summit Grid Reference:  SN 60638 98682 (LIDAR)

Bwlch Height:  112.1m (LIDAR)

Bwlch Grid Reference:  SN 60846 98530 (LIDAR)

Drop:  56.8m (LIDAR)

Dominance:  33.62% (LIDAR)

 

Myrddyn Phillips (September 2024)

 

 

 

  

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

Mynydd Pencarreg (SN 575 432) – Lesser Dominant deletion

There has been a deletion 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 derived from a Trimble GeoXH 6000 summit survey conducted by Myrddyn Phillips and LIDAR bwlch analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

The summit area of Mynydd Pencarreg (SN 575 432)

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, 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 Mynydd Pencarreg and it is the highest point in its own grouping of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4337 road to its south-west and the A482 road to its north-east, and has the town of Llanbedr Pont Steffan (Lampeter) towards the north. 

Extract from the Ordnance Survey 1:50,000 Landranger map

After the original 400m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised and interpolated heights and drop values also included, this hill was listed with an estimated c 138m of drop, based on the 415m 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 c 277m bwlch height, based on interpolation of 10m contouring between 270m – 280m, with these values giving this hill 33.25% dominance. 

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

The summit of this hill was subsequently surveyed with the Trimble GeoXH 6000, resulting in a 414.9m height and with the bwlch having been analysed via 2m LIDAR, resulting in a 276.2m height, these values gave this hill 138.7m of drop and 33.43% domiance, which was sufficient for it to be classified as a Lesser Dominant hill. 

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

However, it was not until the latest 1m 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 Mynydd Pencarreg

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR bwlch analysis coupled with the summit height derived from the Trimble GeoXH 6000 survey, resulting in a 414.9m summit height and a 276.7m bwlch height, with these values giving this hill 138.2m of drop and 33.32% dominance, which is insufficient for Lesser Dominant status. 

 

The full details for the hill are:

Group:  Mynydd Pencarreg

Name:  Mynydd Pencarreg

OS 1:50,000 map:  146

Summit Height:  414.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 57560 43115 (Trimble GeoXH 6000)

Bwlch Height:  276.7m (LIDAR)

Bwlch Grid Reference:  SN 60000 44090 (LIDAR)

Drop:  138.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  33.32% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (July 2024)

 

 

 

 

  

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

Safle Claddu Nant y Caws (SN 468 174) & (SN 469 174) and Cae Mawr (SN 462 175) – Lesser Dominant reclassified to Dual Summit Lesser Dominant

There has been confirmation of 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 derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cae Mawr (SN 462 175) and Safle Claddu Nant y Caws (SN 468 174 & SN 469 174)

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, 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

Dual Summit hills:

A hill classified as a Dual Summit is defined as one which has an extant natural summit coupled with that of a higher artificial summit, with the latter that can be described as stable in character.  In the main, these recent man-made constructions are the result of quarrying activities producing spoil tips, or as in this instance a landfill.  These recent man-made constructions are treated differently to ancient man-made constructions such as hill forts and tumuli, as if the latter are deemed stable and of an earthen character their age dictates that they can be viewed as being permanent in nature and are now effectively a part of the hill.  For those bagging Dual Summit hills, a visit to either the natural high point or the elevated man-made high point is sufficient to claim an ascent of the hill.  With the Dual Summit classification being a relatively new category and fist instigated in January 2018 for a Dual Summit Pedwar. 

The name the hill is now listed by is Safle Claddu Nant y Caws for the higher man-made summit and Cae Mawr for the lower natural summit, 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 the two summits are positioned with the A48 road to their north and a minor road to their south-west, and has the town of Caerfyrddin (Carmarthen) towards the north-west. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, the natural summit was included in the main P30 list with a 155m summit height, based on the spot height adjoined to a triangulation pillar positioned at SN 46405 17608 that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 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 then separated in to its two component parts, with the man-made summit listed with an estimated c 59m of drop, based on an estimated c 156m summit height and an estimated c 97m bwlch height, with both heights based on interpolation of 5m contouring that appeared on the interactive mapping hosted on the OS Maps website.  With the lower natural summit listed with a 155 summit height and the bwlch between these two summits estimated as c 138m, which if separating these hills would give an estimated c 17m of drop.

However, it was not until LIDAR became available that the details for these summits 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 confirmation of the reclassification of this hill to Dual Summit Lesser Dominant status is due to LIDAR analysis, resulting in a 163.8m summit height for the man-made summit and a 155.1m summit height for the natural summit, and a 98.5m bwlch height, with these values giving the man-made summit 65.3m of drop and 39.89% dominance and the natural summit 56.6m of drop and 36.50% dominance, which is sufficient for Dual Summit Lesser Dominant status, with the details for the higher summit prioritised within the list. 

 

The full details for the hill are:

Group:  Mynydd Sylen

Name:  Safle Claddu Nant y Caws (artificial Dual Summit) and Cae Mawr (natural Dual Summit)

OS 1:50,000 map:  159

Summit Height:  163.8m (artificial Dual Summit) and 155.1m (natural Dual Summit) (LIDAR)

Summit Grid Reference:  SN 46899 17416 & SN 46900 17411 (artificial Dual Summit) and SN 46268 17566 (natural Dual Summit) (LIDAR)

Bwlch Height:  98.5m (LIDAR)

Bwlch Grid Reference:  SN 39491 11374 & SN 39493 11375 (LIDAR)

Drop:  65.3m (artificial Dual Summit) and 56.6m (natural Dual Summit) (LIDAR)

Dominance:  39.89% (artificial Dual Summit) and 36.50% (natural Dual Summit) (LIDAR)

 

Myrddyn Phillips (June 2024)

  

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

Carreg Rhoson (SM 672 256) – Dominant deletion

There has been a deletion from the list of the Y Trechol – The Dominant Hills of Wales, with the summit height and its location, the drop, dominance and status of the hill initially derived from detail on the DataMapWales and its status subsequently confirmed from LIDAR analysis conducted by Myrddyn Phillips. 

Carreg Rhoson (SM 672 256) is positioned on the right of this photograph

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, and the list is now available inits 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 Carreg Rhoson, and it is adjoined to the Garn Fawr group of hills which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it forms a part of the islet chain known as Carreg Rhoson, and it is positioned to the west of the Pembrokeshire coast, with the small city of Tyddewi (St David’s) 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 not included in the main P30 list as the small uppermost 30m ring contour that appears on the Ordnance Survey 1:25,000 Explorer map had been missed. 

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 30m summit height, based on interpolation of its uppermost 30m ring contour.  As this hill is the high point of an island it was also listed with an estimated c 30m drop, which was sufficient for it to be classified as a Dominant hill with 100.00% dominance.

However, it was not until the DataMapWales became available online that the details of this hill could be checked against a product viewed as being more accurate than the contouring on the contemporary Ordnance Survey 1:25,000 map.  This mapping has a 28m spot height for this hill and this is similar to the 27.42m summit height produced by the surface analysis programme developed by Joe Nuttall (JNSA) that uses the OS Terrain product where LIDAR coverage is not available. 

Extract from the DataMapWales

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 Carreg Rhoson (SM 672 256)

Therefore, the confirmation of the deletion of this hill from Dominant status is due to LIDAR analysis, resulting in a 29.8m summit height, and as this summit is the high point of an island the drop value is also 29.8m, which is insufficient for Dominant status. 

 

The full details for the hill are:

Group:  Garn Fawr

Name:  Carreg Rhoson

OS 1:50,000 map:  157

Summit Height:  29.8m (LIDAR)

Summit Grid Reference:  SM 67227 25662 (LIDAR)

Bwlch Height:  N/A (island)

Bwlch Grid Reference:  N/A (island)

Drop:  29.8m (LIDAR)

 

Myrddyn Phillips (June 2024)

 

  

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

Pen y Crug (SO 029 303) – Lesser Dominant addition

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 derived from a Trimble GeoXH 6000 survey and LIDAR analysis conducted by Myrddyn Phillips. 

Pen y Crug (SO 029 303)

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 Pen y Crug, and it is adjoined to the Mynydd Epynt group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north and south-west, the B4520 road to its north-east and the A40 road farther to its south, and has the town of Aberhonddu (Brecon) towards the south-east.

When the original 300m 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 331m summit height, based on the spot height adjoined to a triangulation pillar that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 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 108m of drop, based on the 331m summit spot height and an estimated c 223m bwlch height, based on interpolation of 10m contouring between 220m – 230m, resulting in a dominance value of 32.63%, which was insufficient for Lesser Dominant status. 

The Trimble GeoXH 6000 gathering data at the summit of Pen y Crug

The summit of the hill was subsequently surveyed with the Trimble GeoXH 6000, resulting in a 331.2m height, which when combined with the amended bwlch height of an estimated c 222m, based on interpolation of 5m contouring then available on the OS Maps website, gave an estimated c 109m drop and 32.97% dominance value, which was still too low for Lesser Dominant status. 

LIDAR image of Pen y Crug (SO 029 303)

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. 

LIDAR bwlch image of Pen y Crug

Therefore, the addition of this hill to Lesser Dominant status is due to a Trimble GeoXH 6000 summit survey and LIDAR bwlch analysis, resulting in a 331.2m summit height and a 219.9m bwlch height, with these values giving this hill 111.4m of drop and 33.62% dominance, which is sufficient for Lesser Dominant status. 

 

The full details for the hill are:

Group:  Mynydd Epynt

Name:  Pen y Crug

OS 1:50,000 map:  160

Summit Height:  331.2m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 02927 30312 (Trimble GeoXH 6000)

Bwlch Height:  219.9m (LIDAR)

Bwlch Grid Reference:  SO 02162 30880 (LIDAR)

Drop:  111.4m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  33.62% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (March 2024)