Mapping Mountains – Significant Height Revisions – The Welsh Highlands - Uchafion Cymru

 

Welsh Highlands - Uchafion Cymru – Significant Height Revisions

The list to the Welsh Highlands - Uchafion Cymru comprise all Welsh hills at or above 500m in height with 15m minimum drop.  Accompanying the main P15 list are three sub lists; these are the 500m Subs, 490m Subs and the Double Subs with their criteria detailed in the respective Change Registers available on Mapping Mountains.  With details to this list given in the Introduction that was published on Mapping Mountains in November 2015.

The list is co-authored by Myrddyn Phillips and Aled Williams and the posts that have appeared on Mapping Mountains detailing the significant height revisions to the main P15 list and the sub lists appear below presented chronologically in receding order.

Postscript: On the 7^th January 2023 it was announced that the sub hills accompanying the main listing of the Welsh Highlands – Uchafion Cymru now take in just one category, this category is entitled the Welsh Highland Subs.  The criteria for which are all Welsh hills at and above 500m in height with 10m or more and below 15m of drop.

Therefore, the 490m Subs and 490m Double Subs have been dispensed with and the criteria for the 500m Subs that included Welsh hills with 14m or more and below 15m of drop, have been amended to include Welsh hills with 10m or more and below 15m of drop and their title changed to the Welsh Highland Subs.

Mapping Mountains - Significant Height Revisions - The Welsh Highlands - Uchafion Cymru

Mynydd Nodol (SH 865 393) - 42nd significant height revision

Survey post for Mynydd Nodol

 

There has been a Significant Height Revision that is retrospective to a hill that is listed in the 500m Twmpau and The Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 summit survey conducted by Myrddyn Phillips and LIDAR bwlch analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

Mynydd Nodol (SH 865 393)

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

500m Twmpau – Welsh hills at or above 500m and below 600m in height that have 30m minimum drop, with an accompanying sub category entitled the 500m Sub-Twmpau consisting of all Welsh hills at or above 500m and below 600m in height that have 20m or more and below 30m of drop.  With the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.  The list is authored by Myrddyn Phillips and is published on Mapping Mountains in Google Doc format.

500m Twmpau by Myrddyn Phillips

The Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

The Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The name the hill is listed by is Mynydd Nodol and it is adjoined to the Arenig Fawr group of hills, which are situated in the central part of North Wales (Region A, Sub-Region A2), and it is positioned with Llyn Celyn and the A4212 road to its north and a minor road to its south, and has the town of Y Bala towards the south-east.

When the listings of the 500m Twmpau and The Welsh Highlands – Uchafion Cymru were first compiled, this hill was listed with a summit height of 539m, based on the spot height 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

However, it was not until the survey with the Trimble GeoXH 6000 and 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 Trimble GeoXH 6000 gathering data at the summit of Mynydd Nodol

The survey with the Trimble GeoXH 6000 gives the summit of this hill as 540.0m positioned at SH 86514 39339, 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, Harvey or other interactive map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or other GNSS equipment or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 540.0m and this was derived from a Trimble GeoXH 6000 survey, this is 1.0m higher than the originally listed summit height of 539m, which was based on the spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and importantly this height signifies that an uppermost 540m ring contour is missing from this map.

 

The full details for the hill are:

Group:  Arenig Fawr

Name:  Mynydd Nodol

OS 1:50,000 map:  124, 125

Summit Height (New Height):  540.0m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 86514 39339 (Trimble GeoXH 6000)  

Bwlch Height:  370.8m (LIDAR)

Bwlch Grid Reference:  SH 85660 39014 (LIDAR)

Drop:  169.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips and Aled Williams (July 2026)

Mapping Mountains - Significant Height Revisions - The Welsh Highlands - Uchafion Cymru

Craig Nyth y Gigfran (SH 687 461) - 41st significant height revision

There has been a Significant Height Revision to a hill that is listed in The Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams. 

LIDAR image of Craig Nyth y Gigfran (SH 687 461)

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

The Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

The Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The name the hill is listed by is Craig Nyth y Gigfran and it is adjoined to the Moelwyn Mawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A2), and it is positioned with the A470 road to its east and the A496 road to its south-east, and has the town of Blaenau Ffestiniog towards the east.

A basic levelling survey conducted by Myrddyn Phillips on the 30.08.04 gave this hill 43½ft (13.3m) of drop and the hill was therefore listed with an estimated c 529m summit height and an estimated c 516m bwlch height, with both heights based on the basic levelling survey and 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

Since the original compilation of this list 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 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.

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 for this hill is has a 530m summit spot height. 

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 Craig Nyth y Gigfran (SH 687 461)

LIDAR analysis gives the summit of this hill as 530.1m positioned at SH 68732 46178, 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, Harvey or other interactive 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 with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 530.1m and this was derived from LIDAR analysis, this is 1.1m higher than the original estimated c 529m summit height and 10.1m higher than the uppermost 520m contour that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and importantly this height signifies that an uppermost 530m ring contour is missing from this map.

 

The full details for the hill are:

Group:  Moelwyn Mawr

Name:  Craig Nyth y Gigfran

OS 1:50,000 map:  115

Summit Height (New Height):  530.1m (LIDAR)

Summit Grid Reference:  SH 68732 46178 (LIDAR)  

Bwlch Height:  516.9m (LIDAR)

Bwlch Grid Reference:  SH 68649 46174 (LIDAR)

Drop:  13.2m (LIDAR)

 

Myrddyn Phillips and Aled Williams (June 2026)

Mapping Mountains - Significant Height Revisions - The Welsh Highlands - Uchafion Cymru

Craig Ysgafn (SH 660 442) - 40th significant height revision

 

There has been a Significant Height Revision to a hill that is listed in The Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams. 

LIDAR image of Craig Ysgafn (SH 660 442)

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

The Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

The Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The name the hill is listed by is Craig Ysgafn and it is adjoined to the Moelwyn Mawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A2), and it is positioned with the A4085 road to its west, the A487 road to its south and the A496 road to its east, and has the town of Blaenau Ffestiniog towards the east north-east.

Evaluating a summit and bwlch height for this hill based on contour interpolation from contemporary Ordnance Survey maps is difficult, as except for a 640m contour there is no significant independent contour of note 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 Craig Ysgafn (SH 660 442)

LIDAR analysis gives the summit of this hill as 658.2m positioned at SH 66008 44230, 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, Harvey or other interactive 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 with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 658.2m and this was derived from LIDAR analysis, this is 18.2m higher than the uppermost 640m contour that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and importantly this height signifies that an uppermost 650m ring contour is missing from this map.

 

The full details for the hill are:

Group:  Moelwyn Mawr

Name:  Craig Ysgafn

OS 1:50,000 map:  124

Summit Height (New Height):  658.2m (LIDAR)

Summit Grid Reference:  SH 66008 44230 (LIDAR)  

Bwlch Height:  647.9m (LIDAR)

Bwlch Grid Reference:  SH 66012 44249 (LIDAR)

Drop:  10.2m (LIDAR)

 

Myrddyn Phillips and Aled Williams (May 2026)

Mapping Mountains - Significant Height Revisions - The Welsh Highlands - Uchafion Cymru

Craig Ysgafn (SH 659 443) - 39th significant height revision

 

There has been a Significant Height Revision to a hill that is listed in the 600m Twmpau and the The Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams. 

LIDAR image of Craig Ysgafn (SH 659 443)

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

600m Twmpau – Welsh hills at or above 600m and below 700m in height that have 30m minimum drop, with an accompanying sub category entitled the 600m Sub-Twmpau consisting of all Welsh hills at or above 600m and below 700m in height that have 20m or more and below 30m of drop.  With the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.  The list is authored by Myrddyn Phillips and is published on Mapping Mountains in Google Doc format.

600m Twmpau by Myrddyn Phillips

The Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

The Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The name the hill is listed by is Craig Ysgafn and it is adjoined to the Moelwyn Mawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A2), and it is positioned with the A4085 road to its west, the A487 road to its south and the A496 road to its east, and has the town of Blaenau Ffestiniog towards the east north-east.

When the list of Welsh 500m P15s that later became known as the The Welsh Highlands – Uchafion Cymru was first compiled, this hill was listed with an estimated c 26m of drop, based on the 689m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 663m bwlch height, based on interpolation of 10m contouring between 660m – 670m. 

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 Craig Ysgafn (SH 659 443)

LIDAR analysis gives the summit of this hill as 690.0m positioned at SH 65994 44332, and when compared to its originally listed summit height 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, Harvey or other interactive 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 with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 690.0m and this was derived from LIDAR analysis, this is 1.0m higher than the originally listed summit height of 689m, which was based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and importantly this height signifies that an uppermost 690m ring contour is missing from this map.

 

The full details for the hill are:

Group:  Moelwyn Mawr

Name:  Craig Ysgafn

OS 1:50,000 map:  124

Summit Height (New Height):  690.0m (LIDAR)

Summit Grid Reference:  SH 65994 44332 (LIDAR)  

Bwlch Height:  663.4m (LIDAR)

Bwlch Grid Reference:  SH 66001 44596 (LIDAR)

Drop:  26.6m (LIDAR)

 

Myrddyn Phillips and Aled Williams (May 2026) 

Mapping Mountains - Significant Height Revisions - The Welsh Highlands - Uchafion Cymru

Ysgafell Wen (SH 663 487) - 38th significant height revision

 

There has been a Significant Height Revision that is retrospective to a hill that is listed in the Y Pellennig – The Remotest Hills of Wales and the Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Leica RX1250 survey conducted by Alan Dawson. 

LIDAR image of Ysgafell Wen (SH 663 487)

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

Y Pellennig –The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has a minimum 15m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet or print-booklet version on Mapping Mountains Publications with the up-to-date master list available on Mapping Mountains to download in Google Doc format. 

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The name the hill is listed by is Ysgafell Wen and it is adjoined to the Moelwyn Mawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A2), and it is positioned with the A498 road to its north-west, a minor road to its west and the A470 road to its east, and has the town of Blaenau Ffestiniog towards the south-east. 

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

When the original list that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was listed with an estimated c 16m of drop, based on a basic levelling survey conducted by John and Anne Nuttall, with the summit height ascertained by the addition of the drop value to the 641m 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. 

LIDAR summit image of Ysgafell Wen (SH 663 487)

However, it was not until a survey with GNSS equipment that an accurate summit height for this hill could be ascertained.  This was conducted by Alan Dawson on the 12.06.17 using a Leica RX1250, resulting in a 659.0m summit height positioned at SH 66384 48768, 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, the Leica RX1250 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, Leica RX1250 or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 659.0m and this was derived from a Leica RX1250 survey, this is 2.0m higher than the previously listed height of c 657m, which was based on a 16m basic levelling survey conducted by John and Anne Nuttall, with the summit height ascertained by the addition of the drop value to the 641m 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.

 

The full details for the hill are:

Group:  Moelwyn Mawr

Name:  Ysgafell Wen

OS 1:50,000 map:  115

Summit Height (New Height):  659.0m (converted to OSGM15, Leica RX1250) 

Summit Grid Reference:  SH 66384 48768 (Leica RX1250) 

Bwlch Height:  639.9m (converted to OSGM15, Leica RX1250) 

Bwlch Grid Reference:  SH 66380 48665 (Leica RX1250) 

Drop:  19.1m (Leica RX1250) 

Remoteness:  2.760km

 

Myrddyn Phillips and Aled Williams (February 2026)

Mapping Mountains - Significant Height Revisions - The Welsh Highlands - Uchafion Cymru

Yr Eifl (SH 364 447) - 37th significant height revision

Summit Relocations post for Yr Eifl

 

There has been a Significant Height Revision that is retrospective to a hill that is listed in the 500m Twmpau, Y Trechol – The Dominant Hills of Wales and the The Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop, the dominance and status of the hill derived from a Leica GS15 summit survey conducted by John Barnard, Graham Jackson and Myrddyn Phillips, and LIDAR bwlch analysis conducted by Aled Williams. 

Yr Eifl (SH 364 447)

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

500m Twmpau – Welsh hills at or above 500m and below 600m in height that have 30m minimum drop, with an accompanying sub category entitled the 500m Sub-Twmpau consisting of all Welsh hills at or above 500m and below 600m in height that have 20m or more and below 30m of drop.  With the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.  The list is authored by Myrddyn Phillips and is published on Mapping Mountains in Google Doc format.

500m Twmpau by Myrddyn Phillips

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 Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

The Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The name the hill is listed by is Yr Eifl and it is adjoined to its own group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with minor roads to its north-east, the B4417 road to its south and the A499 road to its east, and has the villages of Trefor towards the north north-east and Llithfaen towards the south south-west.

When the listings of the 500m Twmpau, Y Trechol – The Dominant Hills of Wales and The Welsh Highlands – Uchafion Cymru were first compiled, this hill was listed with a summit height of 564m, based on the spot height adjoined to a triangulation pillar 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

However, it was not until the survey with the Leica GS15 that the details for this hill could be accurately re-assessed.  Although the trig pillar is positioned on a relatively stable base it is positioned on the top of a substantial ancient cairn which consists of a multitude of individual stones and rocks and as this is considered as not being permanent in nature, it is the highest remaining natural ground on the periphery of the ancient cairn that is taken as both its listed summit height and summit position, and when compared to its originally listed summit height of 564m 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, Harvey or other interactive map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or other GNSS equipment or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared with the data produced by the Trimble or by LIDAR analysis. 

Gathering data with the Leica GS15 at the listed summit position of Yr Eifl

Therefore, the new listed summit height of this hill is 560.7m and this was derived from a Leica GS15 survey, this is 3.3m lower than the originally listed summit height of 564m, which was 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.

 

The full details for the hill are:

Group:  Yr Eifl

Name:  Yr Eifl

OS 1:50,000 map:  123

Summit Height (New Height):  560.7m (converted to OSGM15, Leica GS15)

Summit Grid Reference:  SH 36482 44734 (Leica GS15)  

Bwlch Height:  129.4m (LIDAR)

Bwlch Grid Reference:  SH 45347 48678 (LIDAR)

Drop:  431.3m (Leica GS15 summit and LIDAR bwlch)

Dominance:  76.92% (Leica GS15 summit and LIDAR bwlch)

 

Myrddyn Phillips and Aled Williams (February 2026)

Mapping Mountains - Significant Height Revisions - The Welsh Highlands - Uchafion Cymru

Pt. 914.9m (SH 659 585) - 36th significant height revision

Survey post for Pt. 914.9m

Hill Reclassifications post for Pt. 914.9m

 

There has been a Significant Height Revision to a hill that is listed in the The Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey conducted by Aled Williams. 

Pt. 914.9m (SH 659 585).  Photo: Aled Williams

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

Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The hill is being listed by the point (Pt. 914.9m) notation, and it is adjoined to the Glyder Fawr 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 A5 road to its north and the A4086 road to its south, and has the village of Capel Curig towards the east.

When the initial P10 sub list was completed in June 2020 this hill was listed with 9.4m of drop, based on a 31ft basic levelling survey conducted by Myrddyn Phillips on the 02.05.99.  However, with no significant independent contour of note on the contemporary Ordnance Survey 1:25,000 Explorer map it was difficult to give this hill an accurate summit height. 

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

The hill was subsequently analysed via LIDAR by Aled Williams, resulting in a 913.9m summit height and a 905.1m bwlch height, with these values giving this hill 8.8m of drop, which was insufficient for it to be classified as a Welsh Highland Sub.  However, with the drop value relatively close to the qualifying criterion of 10m this hill was prioritised for a survey with the Trimble GeoXH 6000. 

The Trimble GeoXH 6000 gathering data at the summit of Pt. 914.9m (SH 659 585).  Photo: Aled Williams

The Trimble GeoXH 6000 survey gives the summit of this hill as 914.9m positioned at SH 65981 58563, 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, Harvey or other interactive 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 with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 914.9m and this was derived from a Trimble GeoXH 6000 survey, this is 14.9m higher than the uppermost 900m contour that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.

 

The full details for the hill are:

Group:  Glyder Fawr

Name:  Pt. 914.9m           

OS 1:50,000 map:  115

Summit Height (New Height):  914.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 65981 58563 (Trimble GeoXH 6000)

Bwlch Height:  904.4m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 65982 58556 (Trimble GeoXH 6000)   

Drop:  10.5m (Trimble GeoXH 6000) 

 

Aled Williams and Myrddyn Phillips (November 2024)