Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

Carreg Wen Fawr (SN 820 624) – Welsh Highland Sub deletion 

There has been a deletion to the listing of 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 Carreg Wen Fawr (SN 820 624)

The criteria for the list that this deletion 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 name the hill is listed by is Carreg Wen Fawr and it is adjoined to the Drygarn Fawr group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its east and south, and has the village of Pontrhydfendigaid towards the west north-west. 

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

When the initial P10 sub list was completed in June 2020 this hill was listed with an estimated c 10m of drop, based on the 527m summit spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and an estimated c 517m bwlch height, based on interpolation of 5m contouring that appeared on online mapping, with an accompanying note stating:

Summit-area height of 1726ft (526.1m) on OS 6" Map (1888) is in a different position to the 527m height given on paper and enlarged-scale online OS maps. 

Extract from the Ordnance Survey series of Six-Inch maps

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

Therefore, the deletion of this hill from Welsh Highland Sub status is due to LIDAR analysis, resulting in a 526.0m summit height and a 516.6m bwlch height, with these values giving this hill 9.4m of drop, which is insufficient for it to be classified as a Welsh Highland Sub. 

 

The full details for the hill are: 

Group:  Drygarn Fawr

Name:  Carreg Wen Fawr

OS 1:50,000 map:  147

Summit Height:  526.0m (LIDAR)

Summit Grid Reference:  SN 82080 62445 (LIDAR)

Bwlch Height:  516.6m (LIDAR)

Bwlch Grid Reference:  SN 82049 62279 (LIDAR)   

Drop:  9.4m (LIDAR) 

 

For the additions, deletions and reclassifications to the Welsh Highlands – Uchafion Cymru reported on Mapping Mountains please consult the following Change Registers:

 

Welsh Highland P15s

 

Welsh Highland Subs

 

Aled Williams and Myrddyn Phillips (January 2024)