Myrddyn Phillips - Mapping Mountains: Mapping Mountains - Hill Reclassifications - Y Trechol

Tuesday 5 May 2020

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.

Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pen y Crug (SO 029 303) – Lesser Dominant addition (93rd reclassification)

Survey post for Pen y Crug

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)

Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Hill Park (SM 955 102) – Lesser Dominant addition (92nd reclassification)

Summit Relocations post for Hill Park

Significant Name Changes post for Hill Park

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 prompted by detail produced by Joe Nuttall in his surface analysis programme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Myrddyn Phillips.

LIDAR image of Hill Park (SM 955 102)

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 inits entirety on Mapping Mountains in Google Doc format.

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is now listed by is Hill Park, and this was derived from the Tithe map, 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 is positioned encircled by minor roads, with the A4076 road farther to its west, and the A477 road to its south-west, and has the village of Johnston towards the 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 with a 99m summit height, based on the spot height that appears on the contemporary 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 31m of drop, based on the 99m summit spot height and an estimated c 68m bwlch height, based on interpolation of 5m contouring between 65m – 70m, resulting with the drop value being insufficient in relation to the summit height for consideration to Lesser Dominant status.

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 99.5m summit height and a 63.6m bwlch height, with these values giving this hill 35.9m of drop and 36.16% dominance which is sufficient for Lesser Dominant status, with the caveat that the bwlch position has been relocated to a rail cutting which conforms with the protocols used in this list.

The full details for the hill are:

Group: Garn Fawr

Name: Hill Park

OS 1:50,000 map: 157, 158

Summit Height: 99.5m (LIDAR)

Summit Grid Reference: SM 95585 10244 (LIDAR)

Bwlch Height: 63.6m (LIDAR)

Bwlch Grid Reference: SM 93281 10622 (LIDAR)

Drop: 35.9m (LIDAR)

Dominance: 36.16% (LIDAR)

Myrddyn Phillips (January 2024)

Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Mynydd Cas-fuwch (SN 028 296) – Lesser Dominant deletion (91st reclassification)

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 LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Mnydd Cas-fuwch (SN 028 296)

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 now listed by is Mynydd Cas-fuwch, and it is adjoined to the Mynydd Preseli group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north-west and south, the B4329 road to its south-east and the B4313 road to its north-east, and has the village of Cas-mael (Puncheston) towards the west.

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

When the original 300m 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 116m of drop and 33.43% dominance, based on the 347m 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 the 231m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger map.

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

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 346.4m summit height and a 231.5m bwlch height, with these values giving this hill 114.9m of drop and 33.17% dominance, which is insufficient for this hill to be classified as a Lesser Dominant.

The full details for the hill are:

Group: Mynydd Preseli

Name: Mynydd Cas-fuwch

OS 1:50,000 map: 145, 157, 158

Summit Height: 346.4m (LIDAR)

Summit Grid Reference: SN 02872 29646 (LIDAR)

Bwlch Height: 231.5m (LIDAR)

Bwlch Grid Reference: SN 05870 29855 & SN 05868 29843 (LIDAR)

Drop: 114.9m (LIDAR)

Dominance: 33.17% (LIDAR)

Myrddyn Phillips (March 2023)

Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Rhos Trebared (SN 173 475) – Lesser Dominant deletion (90th reclassification)

LIDAR image of Rhos Trebared (SN 173 475)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is now listed by is Rhos Trebared and this was derived from local enquiry, and it is adjoined to the Mynydd Bach group of hills, which are situated in the western part of South Wales (Region B, Sub-Region B1), and it is positioned with the coast to its north-west, the B4548 road to its north-east and a minor road to its south, and has the town of Aberteifi (Cardigan) 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 and interpolated heights and drop values also included, this hill was listed with 30m of drop and 43.48% dominance, based on the 69m summit spot height and the 39m bwlch spot height that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

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

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 70.3m summit height and a 40.3m bwlch height, with these values giving this hill 29.9m of drop, which is insufficient for this hill to be classified as a Lesser Dominant.

The full details for the hill are:

Group: Mynydd Bach

Name: Rhos Trebared

OS 1:50,000 map: 145

Summit Height: 70.3m (LIDAR)

Summit Grid Reference: SN 17391 47521 (LIDAR)

Bwlch Height: 40.3m (LIDAR)

Bwlch Grid Reference: SN 17728 47659 (LIDAR)

Drop: 29.9m (LIDAR)

Dominance: drop insufficient for qualification

Myrddyn Phillips (February 2023)

Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Cnwc y Fedwen (SN 382 205) – Lesser Dominant deletion (89th reclassification)

LIDAR image of Cnwc y Fedwen (SN 382 205)

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 now listed by is Cnwc y Fedwen and this was derived from the Tithe map, and it is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north and south-west, and the A40 road to its south, has the town of Caerfyrddin (Carmarthen) towards the 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 and drop values also included, this hill was listed with an estimated c 38m of drop and 34.23% dominance, based on the 111m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 73m bwlch height, based on interpolation of 5m contouring between 70m–75m that appear on the Ordnance Survey 1:25,000 Explorer map.

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

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 111.3m summit height and a 74.4m bwlch height, with these values giving this hill 36.9m of drop and 33.16% of dominance, which is insufficient for this hill to be classified as a Lesser Dominant.

The full details for the hill are:

Group: Mynydd Pencarreg

Name: Cnwc y Fedwen

OS 1:50,000 map: 145, 159

Summit Height: 111.3m (LIDAR)

Summit Grid Reference: SN 38266 20540 (LIDAR)

Bwlch Height: 74.4m (LIDAR)

Bwlch Grid Reference: SN 38881 21445 (LIDAR)

Drop: 36.9m (LIDAR)

Dominance: 33.16%

Myrddyn Phillips (August 2022)

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

Pen y Ddinas (SN 627 357) – Lesser Dominant addition (88th reclassification)

Significant Height Revisions post for Pen y Ddinas

Summit Relocations post for Pen y Ddinas

There has been an addition 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 Pen y Ddinas (SN 627 357)

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 Ddinas and it is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north, the B4337 road to its south-west and the B4302 road to its east, and has the village of Llansawel towards the north-west.

When the original 200m 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 the details for this hill were re-evaluated, and it was listed with an estimated c 53m drop, based on an estimated c 207m summit height and an estimated c 154m bwlch height, with both heights based on interpolation of 10m contouring that appear on the contemporary Ordnance Survey 1:25,000 Explorer map.

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online. Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website. Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online. This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 155m bwlch spot height and when coupled with a re-evaluation of its estimated summit height of c 203m , these values gave this hill an estimated c 48m of drop, which was still insufficient for Lesser Dominant status.

Therefore, the addition of this hill to Lesser Dominant status is due to LIDAR analysis, resulting in a 230.9m summit height and a 153.2m bwlch height, with these values giving this hill 77.7m of drop and 33.63% dominance, which is sufficient for it to be classified as a Lesser Dominant hill.

The full details for the hill are:

Group: Mynydd Pencarreg

Name: Pen y Ddinas

OS 1:50,000 map: 146

Summit Height: 230.9m (LIDAR)

Summit Grid Reference: SN 62756 35746 (LIDAR)

Bwlch Height: 153.2m (LIDAR)

Bwlch Grid Reference: SN 62239 35477 (LIDAR)

Drop: 77.7m (LIDAR)

Dominance: 33.63% (LIDAR)

Myrddyn Phillips (June 2022)

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

Pen Lan Fawr (SN 626 222) – Lesser Dominant addition (87th reclassification)

Significant Height Revisions post for Pen Lan Fawr

LIDAR image of Pen Lan Fawr (SN 626 222)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Pen Lan Fawr and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north, the Afon Tywi to its south and the A483 road to its east, and has the town of Llandeilo 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 was included in the accompanying Hills to be surveyed sub 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 the 95m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 66m bwlch height, based on interpolation of 10m contouring between 60m – 70m.

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 was entitled the Interactive Coverage Map became available online. This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 65m bwlch spot height, and when coupled with the 95m summit spot height these values gave this hill 30m of drop, with this drop value not giving the hill sufficient dominance to be included as a Lesser Dominant hill.

Therefore, the addition of this hill to Lesser Dominant status is due to LIDAR analysis, resulting in a 98.3m summit height and a 64.9m bwlch height, with these values giving this hill 33.4m of drop and 33.97% dominance, which is sufficient for it to be classified as a Lesser Dominant hill.

The full details for the hill are:

Group: Mynydd Mallaen

Name: Pen Lan Fawr

OS 1:50,000 map: 159

Summit Grid Reference: SN 62626 22229 (LIDAR)

Summit Height: 98.3m (LIDAR)

Bwlch Grid Reference: SN 61761 22561 (LIDAR)

Drop Summit to Bwlch: 33.4m (LIDAR)

Drop Bwlch to ODN: 64.9m (LIDAR)

Dominance: 33.97% (LIDAR)

Myrddyn Phillips (April 2022)

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

The Rookery (SN 611 227) – Lesser Dominant reclassified to Dominant (86th 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, dominance and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of The Rookery (SN 611 227)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is The Rookery, and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with the A40 road to its north, a minor road to its west, the Afon Tywi to its south and the A483 road to its east, and has the town of Llandeilo towards the 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 and drop values also included the details for this hill were re-evaluated, and it was listed with an estimated c 49m drop and 48.04% dominance, based on the 102m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 53m bwlch height based on interpolation of 10m contouring between 50m – 60m.

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

LIDAR summit image of The Rookery (SN 611 227)

Therefore, the reclassification of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 102.6m summit height and a 50.3m bwlch height, with these values giving this hill 52.2m drop and 50.94% dominance, which is insufficient for it to be classified as a Dominant hill.

The full details for the hill are:

Group: Mynydd Mallaen

Name: The Rookery

OS 1:50,000 map: 159

Summit Grid Reference: SN 61191 22707 (LIDAR)

Summit Height: 102.6m (LIDAR)

Bwlch Grid Reference: SN 61577 23807 (LIDAR)

Drop Summit to Bwlch: 52.2m (LIDAR)

Drop Bwlch to ODN: 50.3m (LIDAR)

Dominance: 50.94% (LIDAR)

Myrddyn Phillips (April 2022)

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

Moel y Gadair (SH 521 391) – Lesser Dominant addition (85th reclassification)

Summit survey post for Moel y Gadair

Bwlch survey post for Moel y Gadair

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

Moel y Gadair (SH 521 391)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Moel y Gadair and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its south and the A497 road to its north-west, and has the town of Cricieth 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 Hills to be surveyed sub list, as it was considered not to meet the criteria then used for 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 31m of drop and 46.27% dominance, based on the 67m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 36m bwlch height based on interpolation of 10m contouring between 30m – 40m. The details for this hill were subsequently reassessed and its drop value amended to an estimated c 30m based on an estimated bwlch height of c 37m.

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

This hill was then surveyed on the 15^th June 2015 using the Trimble GeoXH 6000, resulting in a 66.7m summit height and a 35.9m bwlch height, with these values seemingly confirming its P30 status.

The Trimble GeoXH 6000 gathering data at the summit of Moel y Gadair

One of a series of surveys conducted at the bwlch on the 15th June 2015

One of the resources recently available online is the mapping on the OS Maps website and the details for this hill were subsequently re-assessed against this mapping. This is the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local. This mapping had bwlch contouring between 35m – 40m, with interpolation placing the height of the bwlch as an estimated c 37m, with the 5m contouring helping to indicate the position of the bwlch.

With the aid of a ten figure grid reference for the bwlch position taken from the 5m contouring on the OS Maps website the bwlch of this hill was re-surveyed using the Trimble GeoXH 6000 on the 23^rd February 2016, resulting in the hill being deleted from Lesser Dominant status.

One of two surveys conducted at the bwlch on the 23rd February 2016

Initial LIDAR analysis indicated that the position of the bwlch was at SH 52007 39290, which is relatively close to where the Trimble GeoXH 6000 was placed on the survey conducted on the 23^rd February 2016. LIDAR gives this position as 36.8m in height and when coupled with the 66.7m summit height, these values gave this hill 29.9m of drop.

LIDAR bwlch image with the joining of the red contour positioned on the road at SH 52007 39290

However, the 36.8m bwlch height ascertained from LIDAR is placed on an artificially raised road which is considered a relatively recent man-made construct and therefore not taken as a part of the height of the bwlch. Further LIDAR analysis was required.

The initial re-assessment of LIDAR was undertaken by Aled Williams and he concluded that this hill is a natural P30, with only the height of the artificially raised road excluding it from being listed as a 30-99m Twmpau. His conclusion was that the height of the bwlch could be listed as an estimated and conservative c 36m or if using remaining natural 35.8m positioned at SH 52020 39324. Either value classifies this hill as a P30 and a Lesser Dominant.

LIDAR image of Moel y Gadair with the white contour placed 30m below the summit indicating this hill is a natural P30 with only the artificially raised road stopping the two respective white contours from being continuous

Having studied LIDAR, I concur with Aled’s conclusion that this hill is a natural P30, the bwlch height quoted is 35.8m positioned at SH 52013 39319. This position is indicated as a joining on the hill to hill traverse excluding the artificially raised road and is approximately four metres from remaining natural ground.

LIDAR image of Moel y Gadair (SH 521 391) showing the various height contours used to conclude this hill is a natural P30 and its bwlch height and position

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 66.7m summit height and a 35.8m bwlch height, with these values giving this hill 30.9m of drop and 46.30% dominance, which is sufficient for it to be classified as a Lesser Dominant hill.

The full details for the hill are:

Group: Moel Hebog

Name: Moel y Gadair

OS 1:50,000 map: 124

Summit Height: 66.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference: SH 52165 39135 (Trimble GeoXH 6000)

Bwlch Grid Reference: SH 52013 39319 (LIDAR)

Drop Summit to Bwlch: 30.9m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Drop Bwlch to ODN: 35.8m (LIDAR)

Dominance: 46.30% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Myrddyn Phillips (March 2022)

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

Dinas Fach (SM 825 226) – Dominant addition (84th reclassification)

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 and status of the hill obtained from the summit analysis programme that uses LIDAR produced by Joe Nuttall, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips.

LIDAR image of Dinas Fach (SM 825 226)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Dinas Fach, 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 a tidal island with its connection to the mainland at low tide positioned to the north-east of its summit, and has the A487 road to its north and the village of Solfach (Solva) 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 the main P30 list or the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used in either category.

Extract from the Ordnance Survey 1:50,000 Landranger 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 remained unlisted, due to a single uppermost ring contour being shown on the Ordnance Survey 1:50,000 Landranger map and intermittent ring contours being shown on the 1:25,000 Explorer map.

Extract from the 1:25,000 Explorer map

Just prior to analysing this hill via LIDAR its details were re-examined against online interactive mapping and it was listed with an estimated c 29m of drop, based on the 30m summit spot height that appears on the Magic Maps website and an estimated c 1m bwlch height, based on interpolation of 5m contouring between 0 – 5m that appears on the Ordnance Survey 1:25,000 Explorer map.

Extract from the Magic Maps website

Therefore, the addition of this hill to Dominant status is due to LIDAR analysis, resulting in a 30.45m summit height and a 0.3m bwlch height, with these values giving this hill 30.15m of drop and 99.01% dominance which is sufficient for Dinas Fach to be classified as a Dominant hill.

The full details for the hill are:

Group: Carn Llidi

Name: Dinas Fach

OS 1:50,000 map: 157

Summit Grid Reference: SM 82559 22659 (LIDAR)

Summit Height: 30.45m (LIDAR)

Bwlch Grid Reference: SM 82605 22745 (LIDAR)

Drop Summit to Bwlch: 30.15m (LIDAR)

Drop Bwlch to ODN: 0.3m (LIDAR)

Dominance: 99.01%

Myrddyn Phillips (October 2021)

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

Ynys Dafydd (SH 646 174) – Dominant addition (83rd reclassification)

Significant Height Revisions post for Ynys Dafydd

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 obtained from the summit analysis programme using LIDAR produced by Joe Nuttall, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips.

LIDAR image of Ynys Dafydd (SH 646 174)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Ynys Dafydd, and it is adjoined to the Rhinogydd group of hills, which are situated in the western part of North Wales (Region A, Sub-Region A3), and it is positioned with the coast to its south-west, the Afon Dyfi (River Dovey) to its south and the A496 road to its north-west, and has the town of Abermaw (Barmouth) 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 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 27m of drop based on an estimated c 42m summit height and an estimated c 15m bwlch height, with both values based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map.

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

Therefore, the addition of this hill to Dominant status is due to LIDAR analysis, resulting in a 52.8m summit height and a 17.1m bwlch height, with these values giving this hill 35.7m of drop and 67.61% dominance which is sufficient for Ynys Dafydd to be classified as a Dominant hill.

The full details for the hill are:

Group: Rhinogydd

Name: Ynys Dafydd

OS 1:50,000 map: 124

Summit Grid Reference: SH 64636 17484 (LIDAR)

Summit Height: 52.8m (LIDAR)

Bwlch Grid Reference: SH 64599 17744 (LIDAR)

Drop Summit to Bwlch: 35.7m (LIDAR)

Drop Bwlch to ODN: 17.1m (LIDAR)

Dominance: 67.61%

Myrddyn Phillips (September 2021)

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

The Park (SN 664 936) – Lesser Dominant reclassified to Dominant (82nd reclassification)

Significant Height Revisions post for The Park

LIDAR image of The Park (SN 664 936)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is The Park, and it is adjoined to the Pumlumon group of hills which are situated in the north-western part of Mid and West Wales (Region B, Sub-Region B2), and it is positioned with the Afon Dyfi to its north, the coast to its west and the A487 road to its east, and has the village of Tal-y-bont 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 and interpolated heights and drop values also included the details for this hill were re-evaluated, and it was listed with an estimated c 41m drop and 49.40% dominance, based on an estimated c 83m summit height and the 42m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

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

Therefore, the reclassification of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in an 85.6m summit height and a 42.7m bwlch height, with these values giving this hill 42.9m drop and 50.09% dominance, which is insufficient for it to be classified as a Dominant hill.

The full details for the hill are:

Group: Pumlumon

Name: The Park

OS 1:50,000 map: 135

Summit Grid Reference: SN 66441 93678 (LIDAR)

Summit Height: 85.6m (LIDAR)

Bwlch Grid Reference: SN 66477 93308 (LIDAR)

Drop Summit to Bwlch: 42.9m (LIDAR)

Drop Bwlch to ODN: 42.7m (LIDAR)

Dominance: 50.09% (LIDAR)

Myrddyn Phillips (July 2021)

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

Llwynderw Hill (SJ 196 036) – Lesser Dominant deletion (81st reclassification)

Survey post for Llwynderw Hill

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

LIDAR image of Llwynderw Hill (SJ 196 036)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Llwynderw Hill and this was derived from local enquiry, and it is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with minor roads to its north, west and south and the A483 road to its south-east, and has the town of Y Trallwng (Welshpool) towards the north-east.

After the original 200m 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 80m of drop and 33.61% dominance, based on the 238m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 158m bwlch height, based on interpolation of 5m contouring between 155m – 160m that appears on the Ordnance Survey 1:25,000 Explorer map.

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

LIDAR analysis confirmed the natural summit position of this hill and decreased its dominance to 33.87%, and as the summit of this hill has now been surveyed with the Trimble GeoXH 6000 it is this result that is being prioritised in preference to the LIDAR height and position, resulting in a summit height of 237.9m positioned at SJ 19600 03662.

The Trimble GeoXH 6000 gathering data at the summit of Llwynderw Hill

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR bwlch analysis and a Trimble GeoXH 6000 summit survey, resulting in a 237.9m summit height and a 159.7m bwlch height, with these values giving this hill 78.3m of drop and 32.89% dominance, which is insufficient for it to be classified as a Lesser Dominant hill.

The full details for the hill are:

Group: Carnedd Wen

Name: Llwynderw Hill

OS 1:50,000 map: 136

Summit Grid Reference: SJ 19600 03662 (Trimble GeoXH 6000)

Summit Height: 237.9m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference: SJ 18827 03989 (LIDAR)

Drop Summit to Bwlch: 78.3m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Drop Bwlch to ODN: 159.7m (LIDAR)

Dominance: 32.89% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Myrddyn Phillips (June 2021)

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

Banc (SN 568 757) – Lesser Dominant deletion (80th reclassification)

Survey post for Banc

Banc (SN 568 757)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is now listed by is Banc and this was derived from the Tithe map, and it is adjoined to the Elenydd group of hills which are situated in the western part of Mid and West Wales (Region B, Sub-Region B2), and it has the coast to its west and the A487 road to its east, and has the village of Llanfarian towards the north-east.

After 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 64m of drop and 33.33% dominance, based on the 192m summit spot height adjoined to a triangulation pillar positioned at SN 56695 75938 and an estimated c 126m bwlch height, based on interpolation of 10m contouring between 120m – 130m that appears on the Ordnance Survey 1:25,000 Explorer map.

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

LIDAR summit image of Banc (SN 568 757)

LIDAR analysis relocated the summit of this hill and decreased its dominance to 33.06%, and as the summit of this hill has now been surveyed with the Trimble GeoXH 6000 it is this result that is being prioritised in preference to the LIDAR height and position, resulting in a summit height of 194.2m positioned at SN 56817 75750.

The Trimble GeoXH 6000 gathering data at the summit of Banc

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR bwlch analysis and a Trimble GeoXH 6000 summit survey, resulting in a 194.2m summit height and a 130.2m bwlch height, with these values giving this hill 64.0m of drop and 32.93% dominance, which is insufficient for it to be classified as a Lesser Dominant hill.

The full details for the hill are:

Group: Elenydd

Name: Banc

OS 1:50,000 map: 135

Summit Grid Reference: SN 56817 75750 (Trimble GeoXH 6000)

Summit Height: 194.2m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference: SN 57845 73062 (LIDAR)

Drop Summit to Bwlch: 64.0m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Drop Bwlch to ODN: 130.2m (LIDAR)

Dominance: 32.93% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Myrddyn Phillips (May 2021)

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

Ynys Fach (SN 668 951) – Dominant addition (79th reclassification)

Significant Height Revisions post for Ynys Fach

Summit Relocations post for Ynys Fach

Significant Name Changes post for Ynys Fach

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 and status of the hill derived by Joe Nuttall who produced a summit analysis programme using LIDAR, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips.

LIDAR image of Ynys Fach (SN 668 951)

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 inits entirety on Mapping Mountains in Google Doc format.

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is now listed by is Ynys Fach, and it is adjoined to the Pumlumon group of hills which are situated in the north-western part of Mid and West Wales (Region B, Sub-Region B2), and it has the A487 road to its south-east and the town of Machynlleth towards the north-east.

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 27m of drop based on an estimated c 34m summit height and an estimated c 7m bwlch height, with both values based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map.

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

Therefore, the reclassification of this hill to Dominant status is due to LIDAR analysis, resulting in a 43.5m summit height and a 2.1m bwlch height, with these values giving this hill 41.3m of drop and 95.10% dominance which is sufficient for Ynys Fach to be classified as a Dominant hill.

The full details for the hill are:

Group: Pumlumon

Name: Ynys Fach

OS 1:50,000 map: 135

Summit Grid Reference: SN 66845 95141 (LIDAR)

Summit Height: 43.5m (LIDAR)

Bwlch Grid Reference: SN 67483 95096 (LIDAR)

Drop Summit to Bwlch: 41.3m (LIDAR)

Drop Bwlch to ODN: 2.1m (LIDAR)

Dominance: 95.10%

Myrddyn Phillips (March 2021)

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

Glan y Morfa (SH 438 679) – Dominant addition (78th reclassification)

Significant Name Changes post for Glan y Morfa

LIDAR image of Glan y Morfa (SH 438 679)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Glan y Morfa and this was derived from the Tithe map, and it 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 positioned with a minor road to its north and the A4421 to its south-east, and has the village of Llangaffo 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 was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

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 27m of drop based on twin tops both with a 59m summit spot height (59m at SH 43811 67899 on the Ordnance Survey 1:25,000 Explorer map and 59m at SH 45087 68972 on the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map) and a bwlch height of 32m that appears as a spot height on the Ordnance Survey 1:25,000 Explorer map.

LIDAR summit image of Glan y Morfa

However, just to the north of where the 32m bwlch spot height is positioned is a railway cutting and it was not until LIDAR became available that an accurate height for this and the summit could be determined. 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 Glan y Morfa

The details produced by LIDAR analysis for the height and position of the railway cutting and a remaining natural bwlch are given below:

Railway Cutting Bwlch: 27.9m at SH 45679 69377

Remaining Natural Bwlch: 31.8m at SH 45155 69373

Therefore, the addition of this hill to the Y Trechol – The Dominant Hills of Wales list is due to LIDAR analysis, resulting in a 59.2m summit height and a 27.9m bwlch height, with these values giving this hill 31.3m of drop and 52.85% dominance, which is sufficient for it to be classified as a Dominant hill. With the caveat that the remaining natural bwlch is 31.8m in height and positioned at SH 45155 69373, which if taken along with the 59.2m summit height would give this hill 27.3m of drop. But as cuttings on the hill to hill traverse are taken as a part of a hill’s drop value in listings I author this hill is now confirmed as a new addition to the listing of Y Trechol – The Dominant Hills of Wales.

The full details for the hill are:

Group: Ynys Môn

Name: Glan y Morfa

OS 1:50,000 map: 114, 115

Summit Grid Reference: SH 43819 67923 (LIDAR)

Summit Height: 59.2m (LIDAR)

Bwlch Grid Reference: SH 45679 69377 (LIDAR)

Drop Summit to Bwlch: 31.3m (LIDAR)

Drop Bwlch to ODN: 27.9m (LIDAR)

Dominance: 52.85%

Myrddyn Phillips (March 2021)

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

Pen y Foel (SH 425 844) – Lesser Dominant reclassified to Dominant (77th reclassification)

Survey post for Pen y Foel

Pen y Foel (SH 425 844)

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

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Pen y Foel and it 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 has the B5111 road to its north-west and south, and has the village of Llannerch-y-medd towards the 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 and drop values also included, this hill was listed with an estimated c 59m of drop and 48.36% dominance, based on an estimated c 122m summit height and an estimated c 63m bwlch height, with each based on interpolation of 5m contouring that appears on the Ordnance Survey 1:25,000 Explorer map.

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

The summit of this hill was subsequently surveyed with the Trimble GeoXH 6000 resulting in a 122.5m height positioned at SH 42575 84415. This resulted in its dominance amended to 49.40%.

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

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

Extract from the Ordnance Survey 1:25,000 Explorer map showing the bwlch of Pen y Foel

LIDAR does not cover the actual bwlch position of this hill, but there is sufficient coverage of the area of this hill’s bwlch for a better interpolated height compared to the position and height of the 62m spot height previously used for the drop and dominance values of this hill.

LIDAR bwlch image of Pen y Foel

Therefore, the reclassification of this hill from Lesser Dominant status is due to a Trimble GeoXH 6000 summit survey and analysis of partial LIDAR bwlch coverage, resulting in a 122.5m summit height and an estimated c 61m bwlch height, with these values giving this hill an estimated c 62m of drop and 50.21% dominance, which is sufficient for it to be classified as a Dominant hill.

The full details for the hill are:

Group: Ynys Môn

Name: Pen y Foel

OS 1:50,000 map: 114, 115

Summit Grid Reference: SH 42575 84415 (Trimble GeoXH 6000)

Summit Height: 122.5m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference: SH 44053 82788 (interpolation)

Drop Summit to Bwlch: c 62m (Trimble GeoXH 6000 summit and interpolation of partial LIDAR bwlch coverage)

Drop Bwlch to ODN: c 61m (interpolation of partial LIDAR coverage)

Dominance: 50.21% (Trimble GeoXH 6000 summit and interpolation of partial LIDAR bwlch coverage)

Myrddyn Phillips (March 2021)

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

Wilcrick Hill (ST 411 878) – Lesser Dominant reclassified to Dominant (76th reclassification)

There has been confirmation of a reclassification 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 Wilcrick Hill (ST 411 878)

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

The name the hill is listed by is Wilcrick Hill 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 B4245 road and the M4 motorway to its north and the A4810 road to its south, and has the city of Casnewydd (Newport) towards the west.

When the original 30-99m 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 34m of drop, based on the 69m summit spot height and the 35m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map. These values were subsequently used when the Y Trechol – The Dominant Hills of Wales list was first compiled and the hill was listed with 49.28% dominance.

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

As the bwlch contouring represented on the Ordnance Survey 1:25,000 Explorer map is between 30m – 35m with the 35m spot height positioned on a road, the drop value for this hill was re-assessed, resulting in an interpolated height of c 33m for its bwlch being used, and this new value gave this hill a drop value of c 36m and 52.17% dominance and resulted in its reclassification to Dominant status.

Therefore, the confirmation of the reclassification of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 69.8m summit height and a 33.3m bwlch height, with these values giving this hill 36.4m of drop and 52.21% dominance, which is sufficient for it to be classified as a Dominant hill.

The full details for the hill are:

Group: Gwent Is Coed

Name: Wilcrick Hill

OS 1:50,000 map: 171, 172

Summit Grid Reference: ST 41128 87829 (LIDAR)

Summit Height: 69.8m (LIDAR)

Bwlch Grid Reference: ST 41353 88003 (LIDAR)

Drop Summit to Bwlch: 36.4m (LIDAR)

Drop Bwlch to ODN: 33.3m (LIDAR)

Dominance: 52.21% (LIDAR)

Myrddyn Phillips (September 2020)

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

Cae Rosser (SO 388 005) – Lesser Dominant reclassified to Dominant (75th reclassification)

Significant Name Changes post for Cae Rosser

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, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cae Rosser (SO 388 005)

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

The name the hill is listed by is Cae Rosser and this was derived from the Tithe map 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 A472 road to its north and the A449 road to its east and the Afon Wysg (River Usk) to the west, and has the town of Brynbuga (Usk) towards the north north-west.

When the original 30-99m 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 c 33m of drop, based on an estimated c 70m summit height and an estimated c 37m bwlch height, with each based on interpolation of 10m contouring 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

Therefore, the reclassification of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 72.7m summit height and a 32.2m bwlch height, with these values giving this hill 40.5m of drop and 55.68% dominance, which is sufficient for it to be classified as a Dominant hill.

The full details for the hill are:

Group: Gwent Is Coed

Name: Cae Rosser

OS 1:50,000 map: 171

Summit Grid Reference: SO 38857 00521 (LIDAR)

Summit Height: 72.7m (LIDAR)

Bwlch Grid Reference: SO 39355 00008 (LIDAR)

Drop Summit to Bwlch: 40.5m (LIDAR)

Drop Bwlch to ODN: 32.2m (LIDAR)

Dominance: 55.68% (LIDAR)

Myrddyn Phillips (July 2020)

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

Cae Scybor (ST 400 985) – Lesser Dominant deletion (74th 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 Cae Scybor (ST 400 985)

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

The name the hill is listed by is Cae Seybôr and this was derived from the Tithe map 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 encircled by minor roads with the A449 road and the Afon Wysg (River Usk) further to the west, and has the town of Brynbuga (Usk) towards the north-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 c 43m of drop, based on the 125m summit spot height and a c 82m bwlch height, with the latter height estimated from interpolation of 5m contouring that along with the summit spot height appears 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 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 although no additional information is shown on this mapping, it was at this time that the interpolated bwlch height was amended to c 83m, and when coupled with the 125m summit height these values give this hill c 42m drop and 33.60% dominance.

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 125.5m summit height and an 83.7m bwlch height, with these values giving this hill 41.8m of drop and 33.29% of dominance, which is insufficient for it to be classified as a Lesser Dominant hill.

The full details for the hill are:

Group: Gwent Is Coed

Name: Cae Scybor

OS 1:50,000 map: 171

Summit Grid Reference: ST 40051 98581 (LIDAR)

Summit Height: 125.5m (LIDAR)

Bwlch Grid Reference: ST 40255 98479 (LIDAR)

Drop Summit to Bwlch: 41.8m (LIDAR)

Drop Bwlch to ODN: 83.7m (LIDAR)

Dominance: 33.29% (LIDAR)

Myrddyn Phillips (June 2020)

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

Long Park (SS 072 984) – Lesser Dominant addition (73rd reclassification)

Significant Name Changes post for Long Park

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height, their locations, the drop, dominance 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 addition applies to are:

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 accompanying Hills to be surveyed sub 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

LIDAR summit image for Long Park

LIDAR bwlch image for Long Park

Therefore, the addition of this hill to Lesser Dominant 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 and 39.34% dominance. 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 Grid Reference: SS 07255 98449 (LIDAR)

Summit Height: 79.2m (LIDAR)

Bwlch Grid Reference: SS 06985 99391 (LIDAR)

Drop Summit to Bwlch: 31.1m (LIDAR)

Drop Bwlch to ODN: 48.0m (LIDAR)

Dominance: 39.34% (LIDAR)

Myrddyn Phillips (May 2020)

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

Cymin (SO 527 125) – Lesser Dominant addition (72nd reclassification)

Significant Name Changes post for Cymin

LIDAR image of Cymin (SO 527 125)

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

The name the hill is listed by is Cymin and it is adjoined to the Fforest y Ddena 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 A4136 road to its north and the A466 road to its south-west, and has the town of Trefynwy (Monmouth) towards the west.

When the original 200m 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 c 86m of drop and 33.46% dominance, based on an estimated c 257m summit height and an estimated c 171m bwlch height, with these heights estimated from interpolation of 5m contouring that appears on the Ordnance Survey 1:25,000 Outdoor Leisure (latterly 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 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 256m spot height on the area of this hill’s summit positioned at SO 527 125, and when coupled with the estimated c 171m bwlch height, these values give this hill c 85m of drop and 33.20% dominance, resulting in its deletion from Lesser Dominant status. The 256m spot height is also shown on Ordnance Survey data that appears on the Magic Maps website.

Extract from the Magic Maps website

LIDAR image of Cymin

Therefore, the addition of this hill to Lesser Dominant status is due to LIDAR analysis, resulting in a 256.4m summit height and a 170.6m bwlch height, with these values giving this hill 85.8m of drop and 33.47% dominance, which is sufficient for this hill to be reinstated to Lesser Dominant status.

The full details for the hill are:

Group: Fforest y Ddena

Name: Cymin

OS 1:50,000 map: 162

Summit Grid Reference: SO 52771 12511 (LIDAR)

Summit Height: 256.4m (LIDAR)

Bwlch Grid Reference: SO 53644 12441 (LIDAR)

Drop Summit to Bwlch: 85.8m (LIDAR)

Drop Bwlch to ODN: 170.6m (LIDAR)

Dominance: 33.47% (LIDAR)

Myrddyn Phillips (April 2020)

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

THIS HILL HAS SUBSEQUENTLY BEEN REINSTATED AS A LESSER DOMINANT

Cymin (SO 527 125) – Lesser Dominant deletion (71st reclassification)

Significant Name Changes post for Cymin

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

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 and gives a 256m spot height on the area of this hill’s summit positioned at SO 527 125, and when coupled with the estimated c 171m bwlch height, these values give this hill c 85m of drop and 33.20% dominance. The 256m spot height is also shown on Ordnance Survey data that appears on the Magic Maps website.

Extract from the Magic Maps website

Therefore, the deletion of this hill from Lesser Dominant status is due to detail on contemporary Ordnance Survey maps, resulting in a 256m summit height and an estimated c 171m bwlch height, with these values giving this hill an estimated c 85m of drop and 33.20% dominance, which is insufficient for this hill’s continued classification as a Lesser Dominant.

The full details for the hill are:

Group: Fforest y Ddena

Name: Cymin

OS 1:50,000 map: 162

Summit Grid Reference: SO 52762 12507 (spot height)

Summit Height: 256m (spot height)

Bwlch Grid Reference: SO 53657 12428 (interpolation)

Drop Summit to Bwlch: c 85m (spot height summit and interpolated bwlch)

Drop Bwlch to ODN: c 171m (interpolation)

Dominance: 33.20% (spot height summit and interpolated bwlch)

Myrddyn Phillips (April 2020)

Tuesday 5 May 2020

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

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