Mapping Mountains – Significant Height Revisions – Y Pellennig – The Remotest Hills of Wales, Welsh Highlands – Uchafion Cymru and 700m Twmpau

 

Pt. 714.3m (SH 627 359) 

There has been a Significant Height Revision to a hill that is listed in the Y Pellennig – The Remotest Hills of Wales, Welsh Highlands – Uchafion Cymru and 700m Twmpau, 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 Pt. 714.3m (SH 627 359)

The criteria for the three 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 Myrddyn Phillips and Aled Williams

700m Twmpau - Welsh hills at or above 700m and below 800m in height with 30m minimum drop, with an accompanying sub list entitled the 700m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 700m and below 800m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.  The list is authored by Myrddyn Phillips and is available to download in Google Doc format from Mapping Mountains. 

The 700m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 714.3m) notation 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 a minor roads to the north, south-west and east, and the A4212 road farther to its north, and has the town of Y Bala towards the east.

When the original list that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was listed with 18m of drop, based on an eye and spirit level survey conducted by John and Anne Nuttall that resulted in 60ft (18.3m) of drop, and it was originally listed with a 712m summit height based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and a 694m bwlch height. 

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 Pt. 714.3m (SH 627 359)

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 714.3m and this was derived from LIDAR analysis, this is 2.3m higher than the previously listed height of 712m which was based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Arenig Fawr

Name:  Pt. 714.3m

OS 1:50,000 map:  124, 125

Summit Height (New Height):  714.3m (LIDAR) 

Summit Grid Reference:  SH 82741 35938 (LIDAR) 

Bwlch Height:  693.6m (LIDAR) 

Bwlch Grid Reference:  SH 82725 36128 (LIDAR) 

Drop:  20.7m (LIDAR) 

Remoteness:  2.925km

 

Myrddyn Phillips and Aled Williams (August 2023)

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

Llechwedd Du (SH 893 446) 

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 for the Welsh Highlands – Uchafion Cymru list authored by Aled Williams and Myrddyn Phillips. 

LIDAR image of Llechwedd Du (SH 893 446)

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 Myrddyn Phillips and Aled Williams

The name the hill is listed by is Llechwedd Du and it is adjoined to the Carnedd y Filiast group of hills, which are situated in the central part of North Wales (Region A, Sub-Region A2), and is positioned with the A4212 road to its south and the B4501 road to its east, and has the town of Y Bala towards the south south-east and the village of Cerrigydrudion towards the north-east. 

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

When the original list that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was included as a Welsh Highland Sub with 14m of drop, based on the 509m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 495m bwlch spot height that 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 OS Maps website became available online.  This is the replacement for OS Get-a-map and had contours at 5m intervals which were consistently more accurate compared to the 5m contours that sometimes appeared on Ordnance Survey 1:25,000 Explorer maps and the online Vector Map Local.  This re-assessment resulted in its reclassification to Welsh Highland P15 status and listed with an estimated c 16m of drop, based on an estimated c 511m summit height from interpolation of the 510m uppermost contour and the 495m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map. 

Extract from the interactive mapping hosted on the OS Maps website

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

LIDAR analysis gives the highest ground on this hill as 511.4m positioned at SH 89360 44629, 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, the new listed summit height of this hill is 511.4m and this was derived from LIDAR analysis, this is positioned at SH 89360 44629 and is 2.4m higher than its originally listed height of 509m, which was based on the summit spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Carnedd y Filiast

Name:  Llechwedd Du

OS 1:50,000 map:  124, 125

Summit Height (New Height):  511.4m (LIDAR)

Summit Grid Reference:  SH 89360 44629 (LIDAR)

Bwlch Height:  497.1m (LIDAR)

Bwlch Grid Reference:  SH 89096 44273 (LIDAR)   

Drop:  14.3m (LIDAR) 

 

Myrddyn Phillips and Aled Williams (May 2023)

  

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

 

Castell y Gwynt (SH 653 581) 

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 two Trimble GeoXH 6000 surveys conducted by Myrddyn Phillips on the 16.05.14 and Aled Williams on the 04.03.23. 

Castell y Gwynt (SH 653 581)

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 Myrddyn Phillips and Aled Williams

The name the hill is listed by is Castell y Gwynt 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 list that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was listed with 16m of drop, based on a series of basic levelling surveys conducted by Myrddyn Phillips and listed with a 972m summit height, based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map and a 956m bwlch height, based on the height difference between the summit spot height and the drop value ascertained from the basic levelling survey. 

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

The summit of this hill has now been surveyed twice with the Trimble GeoXH 6000 and it is the average of these results that is being taken, resulting in a 975.7m summit height positioned at SH 65397 58181, and this height 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 Castell y Gwynt on the 16.05.14

Therefore, the new listed summit height of this hill is 975.7m and this was derived from the average of two Trimble GeoXH 6000 surveys, this is positioned at SH 65397 58181 and is 3.7m higher than its previously listed height of 972m which was based on the summit spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Glyder Fawr

Name:  Castell y Gwynt

OS 1:50,000 map:  115

Summit Height (New Height):  975.7m (converted to OSGM15)

Summit Grid Reference:  SH 65397 58181  

Bwlch Height:  959.7m (converted to OSGM15)

Bwlch Grid Reference:  SH 65419 58194

Drop:  16.0m

 

Myrddyn Phillips and Aled Williams (May 2023)

 

 

 

 

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

Craig Eigiau (SH 712 646) 

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 a Trimble GeoXH 6000 survey conducted by Aled Williams. 

Craig Eigiau (SH 712 646) (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 Myrddyn Phillips and Aled Williams

The name the hill is listed by is Craig Eigiau and it is adjoined to the Carnedd Llywelyn 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-east, the A5 road to its south-west and the B5106 road and the A470 road to its east, and has the town of Llanrwst towards the east south-east.

The contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map do not show any meaning contours for this hill that imply its true height, as each only has an uppermost 670m contour. 

Extract from the Ordnance Survey 1:25,00 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 analysis gives this hill 9.7m of drop, based on a 688.1m summit height and a 678.4m bwlch height.  This hill has now been surveyed with the Trimble GeoXH 6000, resulting in a 688.4m summit height positioned at SH 71280 64670 and it is this result that is being prioritised for this hill, and this summit height 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 Craig Eigiau (SH 712 646) (Photo: Aled Williams)

Therefore, the new listed summit height of this hill is 688.4m and this was derived from a Trimble GeoXH 6000 survey, this is positioned at SH 71280 64670 and is 18.4m higher than the uppermost 670m contour on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are: 

Group:  Carnedd Llywelyn

Name:  Craig Eigiau

OS 1:50,000 map:  115

Summit Height (New Height):  688.4m (converted to OSGM15)

Summit Grid Reference:  SH 71280 64670

Bwlch Height:  678.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 71218 64674   

Drop:  10.2m 

 

Aled Williams and Myrddyn Phillips (April 2023)

 

 

  

Mapping Mountains – Significant Height Revisions – 500m Twmpau and Welsh Highlands – Uchafion Cymru

 

Blorens (SO 269 118) 

There has been a Significant Height Revision 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 survey and LIDAR analysis conducted by Aled Williams and Myrddyn Phillips. 

Blorens (SO 269 118)

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.

The 500m Twmpau by Myrddyn Phillips

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 Myrddyn Phillips and Aled Williams

The name the hill is listed by is Blorens and it is adjoined to the Cefn yr Ystrad group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with the A465 road to its north-east, the B4246 road to its north-west and a minor road to its south, and has the town of Y Fenni (Abergavenny) towards the north-east.

When the list of Welsh 500m P15s that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was listed with an estimated c 133m of drop, based on the 561m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 428m bwlch height, based on interpolation of 10m contouring between 420m – 430m. 

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

The summit of this hill has now been surveyed with the Trimble GeoXH 6000, resulting in a 558.9m summit height positioned at SO 26974 11830, and this height 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 Blorens 

Therefore, the new listed summit height of this hill is 558.9m and this was derived from a Trimble GeoXH 6000 survey, this is positioned at SO 26974 11830 and is 2.1m lower than its originally listed height of 561m, which was based on the summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Cefn yr Ystrad

Name:  Blorens

OS 1:50,000 map:  161

Summit Height (New Height):  558.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 26974 11830 (Trimble GeoXH 6000)  

Bwlch Height:  426.9m (LIDAR)

Bwlch Grid Reference:  SO 21949 10939 (LIDAR)

Drop:  132.0m (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Aled Williams and Myrddyn Phillips (March 2023)