Mapping Mountains – Significant Height Revisions – The Welsh P15s

 

The Welsh P15s – Significant Height Revisions

The Welsh P15s are all Welsh hills that have a minimum of 15m of drop, irrespective of their height.  Accompanying the main P15 list is a sub list entitled; The Welsh Sub-P15s, with the qualification to this sub category being all Welsh hills with 14m or more and below 15m of drop.

The list is authored by Myrddyn Phillips and the posts that have appeared on Mapping Mountains detailing the significant height revisions to the main P15 list and the sub list that are below P20 and therefore documented in other lists, appear below presented chronologically in receding order.

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Comin Gwauncaegurwen (SN 711 123) - 14th significant height revision

Hill Reclassifications post for Comin Gwauncaegurwen

Significant Name Changes post for Comin Gwauncaegurwen

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Comin Gwauncaegurwen (SN 711 123)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Comin Gwauncaegurwen and this was derived from the Tithe map with the language protocol also used, and it is adjoined to the Mynydd Du group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with the A4068 road to its north-east, the A4069 road to its north-west and a minor road to its south, and has the village of Brynaman towards the north. 

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

When the listing that became known as The Welsh P15s was being compiled, this hill was not included in the main P15 list or the accompanying P14 sub list, as it possessed no contours of significance on either the Ordnance Survey 1:50,000 Landranger or the 1:25,000 Explorer map. 

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

Since the initial compilation of this list started there have been a number of Ordnance Survey 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 are current and digitally updated such as the mapping on the Magic Maps website.

One of the mapping resources now available online is the WalkLakes website which hosts an interactive map originated from the Ordnance Survey Open Data programme.  This map has many spot heights not on other publicly available maps and a 216m spot height is given on the summit area of this hill. 

Extract from the interactive mapping hosted on the WalkLakes 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 Comin Gawuncaegurwen (SN 711 123)

The summit height produced by LIDAR analysis is 216.6m and when compared to detail on the Ordnance Survey 1:50,000 Landranger and the 1:25,000 Explorer map, this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 216.6m and this was derived from LIDAR analysis.  This is 16.6m higher than the uppermost 200m contour on the contemporary Ordnance Survey 1:50,000 Landranger map and 26.6m higher than the uppermost 190m contour on the Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  Mynydd Du 

Name:  Comin Gawuncaegurwen 

OS 1:50,000 map:  160

Summit Height (New Height):  216.6 (LIDAR)                                                           

Summit Grid Reference:  SN 71158 12343 (LIDAR) 

Bwlch Height:  196.6m (LIDAR) 

Bwlch Grid Reference:  SN 71330 12592 & SN 71332 12592 (LIDAR) 

Drop:  19.98m (LIDAR) 

 

Myrddyn Phillips (April 2024)

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Tywyn Niwbwrch (SH 419 625) - 13th significant height revision

Hill Reclassifications post for Tywyn Niwbwrch

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Tywyn Niwbwrch (SH 419 625)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Tywyn Niwbwrch 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 the coast to its south-west and the A4080 road to its north-east, and has the village of Niwbwrch (Newborough) towards the north. 

When the listing that became known as The Welsh P15s was being compiled, this hill was not included in either the main P15 list or the accompanying P14 sub list, as it possessed no contours of significance on either the Ordnance Survey 1:50,000 Landranger or the 1:25,000 Explorer map. 

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

Since the initial compilation of this list started there have been a number of Ordnance Survey 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 are current and digitally updated such as the mapping on the Magic Maps website. 

One of the mapping resources now available online is the Magic Maps website which hosts an interactive map originated from Ordnance Survey data.  This map has many spot heights not on other publicly available Ordnance Survey maps and for this hill a 27m spot height is given on the area of its summit. 

Extract from the Magic Maps website

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

LIDAR summit image of Tywyn Niwbwrch (SH 419 625)

The summit height produced by LIDAR analysis is 26.9m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 26.9m and this was derived from LIDAR analysis.  This is 26.9m higher than detail on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map which do not give any significant contours for this area, but its new listed summit height is similar to the 27m spot height that appears on the interactive mapping on the Magic Maps website. 

 

The full details for the hill are:

Group:  Ynys Môn 

Name:  Tywyn Niwbwrch 

OS 1:50,000 map:  114, 115

Summit Height (New Height):  26.9m (LIDAR)                                                           

Summit Grid Reference:  SH 41937 62552 (LIDAR) 

Bwlch Height:  8.4m (LIDAR) 

Bwlch Grid Reference:  SH 41804 62760 (LIDAR) 

Drop:  18.4m (LIDAR) 

 

Myrddyn Phillips (October 2021)

 

 

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Maes Llwyn (SH 435 920) - 12th significant height revision

Summit Relocations post for Maes Llwyn

Significant Name Changes post for Maes Llwyn

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Maes Llwyn (SH 435 920)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Maes Llwyn 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 the coast to its north and is encircled by minor roads with the B5111 road and the A5025 road farther to its north and also east, and has the town of Amlwch towards the north-east. 

When the listing that became known as The Welsh P15s was being compiled, this hill was listed with 25m of drop, based on the 77m summit spot height positioned on or near to a covered reservoir that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and the 52m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger map. 

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

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

LIDAR summit image of Maes Llwyn

The height produced by LIDAR analysis to a remaining natural summit is 74.0m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 74.0m and this was derived from LIDAR analysis, this is 3m lower than the previous listed summit height of 77m which was based on the spot height positioned on or near to a covered reservoir that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

 

The full details for the hill are:

Group:  Ynys Môn 

Name:  Maes Llwyn 

OS 1:50,000 map:  114

Summit Height (New Height):  74.0m (LIDAR) 

Summit Grid Reference:  SH 43593 92022 (LIDAR) 

Bwlch Height:  54.9m (LIDAR) 

Bwlch Grid Reference:  SH 43658 91747 (LIDAR) 

Drop:  19.1m (LIDAR) 

 

Myrddyn Phillips (September 2021)

 

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Pen Ucheldref (SH 349 882) - 11th significant height revision

Summit Relocations post for Pen Ucheldref

Significant Name Changes post for Pen Ucheldref

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pen Ucheldref (SH 349 882)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Pen Ucheldref 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 two minor roads beside its summit and the A5025 road to its north-west, and has the village of Llanrhuddlad also towards the north-west. 

When the listing that became known as The Welsh P15s was being compiled, this hill was listed with an estimated c 23m of drop, based on an estimated c 90m summit height and an estimated c 67m bwlch height, with both heights based on interpolation of 5m contouring that appears on the Ordnance Survey 1:25,000 Explorer map, with the 85m upper summit contour mistaken for 90m. 

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

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

The summit height produced by LIDAR analysis is 85.4m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 85.4m and this was derived from LIDAR analysis, this is 4.6m lower than the previous listed summit height of c 90m which was based on interpolation of 5m contouring that appears on the Ordnance Survey 1:25,000 Explorer map, with the 85m upper summit contour mistaken for 90m.

 

The full details for the hill are:

Group:  Ynys Môn 

Name:  Pen Ucheldref 

OS 1:50,000 map:  114

Summit Height (New Height):  85.4m (LIDAR) 

Summit Grid Reference:  SH 34917 88259 (LIDAR) 

Bwlch Height:  c 67m (interpolation) 

Bwlch Grid Reference:  SH 35183 88544 (interpolation) 

Drop:  c 18m (LIDAR summit and interpolated bwlch) 

 

Myrddyn Phillips (August 2021)

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Tregynrig Fawr (SH 402 924) - 10th significant height revision

Significant Name Changes post for Tregynrig Fawr

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, 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 Tregynrig Fawr (SH 402 924)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Tregynrig Fawr 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 the coast and the A5025 road to its north, minor roads to its west, south and east, and has the town of Amlwch towards the east. 

When the listing that became known as The Welsh P15s was being compiled, this hill was listed with an estimated c 16m of drop, based on an estimated c 64m summit height and an estimated c 48m bwlch height, with both heights 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

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 Tregynrig Fawr (SH 402 924)

The summit height produced by LIDAR analysis is 66.5m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 66.5m and this was derived from LIDAR analysis, this is 2.5m higher than the previous listed summit height of c 64m which was based on interpolation of 5m contouring that appears on the Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  Ynys Môn 

Name:  Tregynrig Fawr 

OS 1:50,000 map:  114

Summit Height (New Height):  66.5m (LIDAR)                                                           

Summit Grid Reference:  SH 40239 92455 & SH 40241 92457 (LIDAR) 

Bwlch Height:  47.1m (LIDAR) 

Bwlch Grid Reference:  SH 40184 93235 (LIDAR) 

Drop:  19.3m (LIDAR) 

 

Myrddyn Phillips (August 2021)

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Llanlleiana Park (SH 386 946) - 9th significant height revision

Hill Reclassifications post for Llanlleiana Park

Significant Name Changes post for Llanlleiana Park

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data. 

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Llanlleiana Park 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 the coast to its north, a minor road and the A5025 road farther to its south, and has the village of Cemaes towards the south-west. 

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the main P15 list with an estimated c 16m of drop, based on the 44m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and an estimated c 28m bwlch height based on interpolation of 5m contouring between 25m – 30m that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

The details for this hill have subsequently been re-assessed against the current Ordnance Survey interactive map hosted on the Geograph website which gives a 46m summit spot height, and current 5m contouring at the bwlch which is between 30m – 35m and estimated as c 32m, with these values giving this hill an estimated c 14m of drop, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Extract from the Ordnance Survey interactive mapping hosted on the Geograph website

Therefore, this hill’s new listed summit height is 46m and this was derived from the Ordnance Survey interactive map hosted on the Geograph website, this is 2m higher than the previous listed summit height of 44m which appeared as a spot height on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Llanlleiana Park 

OS 1:50,000 map:  114

Summit Height (New Height):  46m (spot height)                                                           

Summit Grid Reference:  SH 38614 94695 (spot height) 

Bwlch Height:  c 32m (interpolation) 

Bwlch Grid Reference:  SH 38606 94628 (interpolation) 

Drop:  c 14m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (July 2021)

 

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Llanlleiana Park (SH 388 946) - 8th significant height revision

Significant Name Changes post for Llanlleiana Park

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data. 

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Llanlleiana Park 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 the coast to its north, a minor road to its south and the A5025 road farther to its south, and has the village of Cemaes towards the south-west. 

When the listing that became known as The Welsh P15s was being compiled, this hill was listed with an estimated c 15m of drop based on an estimated c 52m summit height and an estimated c 37m bwlch height, with both heights based on interpolation of 5m contouring that appears on the Ordnance 1:25,000 Explorer map. 

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

The details for this hill have been re-evaluated and it is now listed with a 55m summit height, based on the spot height that appears on the Ordnance Survey interactive mapping hosted on the Geograph website, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Extract from the Ordnance Survey interactive mapping hosted on the Geograph website

Therefore, this hill’s new listed summit height is 55m and this was derived from the summit spot height that appears on the Ordnance Survey interactive mapping hosted on the Geograph website, this is 3m higher than the previous listed summit height of c 52m which was based on interpolation of the uppermost 50m ring contour that appears on the Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Llanlleiana Park 

OS 1:50,000 map:  114

Summit Height (New Height):  55m (spot height) 

Summit Grid Reference:  SH 38859 94607 (spot height) 

Bwlch Height:  c 38m (interpolation) 

Bwlch Grid Reference:  SH 38902 94509 (interpolation) 

Drop:  c 17m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (July 2021)

 

 

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Ysgellog & Minffordd (SH 409 912) - 7th significant height revision

Significant Name Changes post for Ysgellog & Minffordd

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Ysgellog & Minffordd (SH 409 912)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Ysgellog & Minffordd 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 encircled by minor roads with the A5025 road farther to the north and the B5111 road farther to the south-east, and has the town of Amlwch towards the east north-east. 

When the listing that became known as The Welsh P15s was being compiled, this hill was listed with an estimated c 23m of drop based on an estimated c 65m summit height and the 42m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

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

The summit height produced by LIDAR analysis is 60.2m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 60.2m and this was derived from LIDAR analysis, this is 4.8m lower than the previous listed summit height of c 65m which was based on interpolation of what was thought to be an uppermost 65m ring contour that appears on the Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Ysgellog & Minffordd 

OS 1:50,000 map:  114

Summit Height (New Height):  60.2m (LIDAR) 

Summit Grid Reference:  SH 40921 91218 & SH 40923 91218 & SH 40925 91220 (LIDAR) 

Bwlch Height:  41.7m (LIDAR) 

Bwlch Grid Reference:  SH 40915 91509 (LIDAR) 

Drop:  18.5m (LIDAR) 

 

Myrddyn Phillips (July 2021)

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Plas Cemlyn (SH 327 936) - 6th significant height revision

Significant Name Changes post for Plas Cemlyn

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, 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 Plas Cemlyn (SH 327 936)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Plas Cemlyn 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 almost entirely surrounded by the coast with minor roads to its south and south-east, and has the village of Cemaes towards the east. 

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

When the listing that became known as The Welsh P15s was being compiled, this hill was listed with an estimated c 15m of drop, based on the 18m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, with this spot height now appearing on the interactive mapping on the Magic Maps website and an estimated c 3m bwlch height based on interpolation of 5m contouring between 0 – 5m. 

Extract from the Magic Maps website

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

The summit height produced by LIDAR analysis is 20.3m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

LIDAR summit image of Plas Cemlyn

Therefore, this hill’s new listed summit height is 20.3m and this was derived from LIDAR analysis, this is 2.3m higher than the previous listed summit height of 18m which was based on the summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

 

The full details for the hill are:

Group:  Ynys Môn 

Name:  Plas Cemlyn 

OS 1:50,000 map:  114

Summit Height (New Height):  20.3m (LIDAR)                                                           

Summit Grid Reference:  SH 32729 93641 (LIDAR) 

Bwlch Height:  2.3m (LIDAR) 

Bwlch Grid Reference:  SH 32454 93517 (LIDAR) 

Drop:  18.0m (LIDAR) 

 

Myrddyn Phillips (June 2021)

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Wylfa (SH 353 936) - 5th significant height revision

Significant Name Changes post for Wylfa

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, 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 Wylfa (SH 353 936)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Wylfa 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 the coast to its north, west and east and a minor road and the A5025 road farther to its south-east, and has the village of Cemaes towards the east. 

When the listing that became known as The Welsh P15s was being compiled, this hill was listed with an estimated c 18m of drop, based on an estimated c 36m summit height and an estimated c 18m bwlch height, with both heights based on interpolation of 5m contouring that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

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

LIDAR summit image of Wylfa (SH 353 936)

The summit height produced by LIDAR analysis is 38.2m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 38.2m and this was derived from LIDAR analysis, this is 2.2m higher than the previous listed summit height of c 36m which was estimated from interpolation of 5m contouring that appear on the Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  Ynys Môn 

Name:  Wylfa 

OS 1:50,000 map:  114

Summit Height (New Height):  38.2m (LIDAR)                                                           

Summit Grid Reference:  SH 35343 93609 (LIDAR) 

Bwlch Height:  20.45m (LIDAR) 

Bwlch Grid Reference:  SH 35438 93650 (LIDAR) 

Drop:  17.8m (LIDAR) 

 

Myrddyn Phillips (June 2021)

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Parc y Ffynnon (SH 634 808) - 4th significant height revision

Hill Reclassifications post for Parc y Ffynnon

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Parc y Ffynnon (SH 634 808)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillps

The name the hill is listed by is Parc y Ffynnon 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 the coast to its north, south and east and a minor road to its immediate west, and has the village of Llangoed towards the south-west. 

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the P14 sub list with 14m of drop, based on the 59m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 44m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

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

LIDAR summit image of Parc y Ffynnon

The summit height produced by LIDAR analysis is 60.6m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 60.6m and this was derived from LIDAR analysis, this is 1.6m higher than the previous listed summit height of 59m that appears as a spot height on the Ordnance Survey 1:25,000 Explorer map.

 

The full details for the hill are:

Group:  Ynys Môn 

Name:  Parc y Ffynnon 

OS 1:50,000 map:  114, 115

Summit Height (New Height):  60.6m (LIDAR)                                                           

Summit Grid Reference:  SH 63430 80880 (LIDAR) 

Bwlch Height:  44.8m (LIDAR) 

Bwlch Grid Reference:  SH 63199 81029 (LIDAR) 

Drop:  15.8m (LIDAR) 

 

Myrddyn Phillips (June 2021)

 

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Bryn Llwyd (SH 396 644) - 3rd significant height revision

Hill Reclassifications post for Bryn Llwyd

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Bryn Llwyd (SH 396 644)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Bryn Llwyd 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 encircled by the Newborough Forest, and has the coast to its south-west and the A4080 road to its north-east, and has the village of Niwbwrch (Newborough) towards the east north-east. 

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the main P15 list with an estimated c 15m of drop, based on an estimated c 46m summit height and an estimated c 31m bwlch height, with both heights based on interpolation of 5m contouring that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

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

LIDAR summit image of Bryn Llwyd

The summit height produced by LIDAR analysis is 43.4m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 43.4m and this was derived from LIDAR analysis, this is 2.6m lower than the previous listed summit height of c 46m which was based on interpolation of the uppermost 45m ring contour that appears on the Ordnance Survey 1:25,000 Explorer map.

 

The full details for the hill are:

Group:  Ynys Môn 

Name:  Bryn Llwyd 

OS 1:50,000 map:  114

Summit Height (New Height):  43.4m (LIDAR)                                                           

Summit Grid Reference:  SH 39665 64415 (LIDAR) 

Bwlch Height:  28.6m (LIDAR) 

Bwlch Grid Reference:  SH 39795 64510 (LIDAR) 

Drop:  14.9m (LIDAR) 

 

Myrddyn Phillips (May 2021)

 

 

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Craig Dinas (SH 280 772) - 2nd significant height revision

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Craig Dinas (SH 280 772)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Craig Dinas 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 the B4545 road to its north and a minor road to its west, and has the village of Trearddur towards the north-west. 

When the listing that became known as The Welsh P15s was being compiled, this hill was listed with an estimated c 16m of drop, based on the 19m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 3m bwlch height based on interpolation of 5m contouring between 0 – 5m. 

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

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

The summit height produced by LIDAR analysis is 20.0m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

LIDAR summit image of Craig Dinas

Therefore, this hill’s new listed summit height is 20.0m and this was derived from LIDAR analysis, this is 1.0m higher than the previous listed summit height of 19m which was based on the summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

 

The full details for the hill are:

Group:  Ynys Môn 

Name:  Craig Dinas 

OS 1:50,000 map:  114

Summit Height (New Height):  20.0m (LIDAR)                                                           

Summit Grid Reference:  SH 28016 77284 (LIDAR) 

Bwlch Height:  3.3m (LIDAR) 

Bwlch Grid Reference:  SH 27937 77186 (LIDAR) 

Drop:  16.7m (LIDAR) 

 

Myrddyn Phillips (May 2021)

 

Mapping Mountains - Significant Height Revisions - The Welsh P15s

Tomen y Mur (SH 705 386) - 1st significant height revision

Survey post for Tomen y Mur

Hill Reclassifications post for Tomen y Mur

 

There has been a Significant Height Revision to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

Tomen y Mur (SH 705 386)

The criteria for the list that this height revision applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Tomen y Mur, and it is adjoined to the Arenig group of hills, which are situated in the central part of North Wales (Region A, Sub-Region A3), and it is positioned with a minor road to its immediate north, the A470 road to its west and further to its north, and has the village of Trawsfynydd towards the south. 

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

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the sub list with an estimated c 14m of drop, based on an estimated c 300m summit height and an estimated c 286m bwlch height, with the former based on interpolation of the uppermost 300m ring contour that appears on the WalkLakes interactive map and the latter based on interpolation of 10m contouring between 280m – 290m that appears on the Ordnance Survey 1:25,000 Explorer map and the mapping on the WalkLakes website. 

Extract from the WalkLakes 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 Tomen y Mur (SH 705 386)

The summit height produced by LIDAR analysis is 303.3m, and as the summit has now been surveyed with the Trimble GeoXH 6000 it is this result that is being prioritised for listing purposes, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

The Trimble GeoXH 6000 gathering data at the summit of Tomen y Mur

Therefore, this hill’s new listed summit height is 303.2m and this was derived from a Trimble GeoXH 6000 survey, this is 3.2m higher than the previous listed summit height of c 300m which was derived from interpolation of the uppermost 300m ring contour that appears on the WalkLakes interactive map.

 

The full details for the hill are:

Group:  Arenig 

Name:  Tomen y Mur 

OS 1:50,000 map:  124

Summit Height (New Height):  303.2m (converted to OSGM15, Trimble GeoXH 6000)  

Summit Grid Reference:  SH 70544 38679 (Trimble GeoXH 6000) 

Bwlch Height:  288.1m (LIDAR) 

Bwlch Grid Reference:  SH 70674 38754 (LIDAR) 

Drop:  15.1m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

Myrddyn Phillips (April 2021)