Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

Cerrig Duon (SJ 128 384) – 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 Cerrig Duon (SJ 128 384)

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 Myrddyn Phillips and Aled Williams

The name the hill is listed by is Cerrig Duon and it is adjoined to the Craig Berwyn group of hills, which are situated in the eastern part of North Wales (Region A, Sub-Region A3), and it is positioned with a minor road to its north-east and the A5 road to its north, and has the town of Llangollen towards the east north-east.

When the initial P10 sub list was completed in June 2020 this hill was listed with an estimated c 12m of drop, based on the 551m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 539m bwlch height, based on interpolation of 5m contouring that appeared online. 

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

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

Therefore, the deletion of this hill from Welsh Highland Sub status is due to LIDAR analysis, resulting in a 549.3m summit height and a 540.0m bwlch height, with these values giving this hill 9.3m of drop, which is insufficient for it to be classified as a Welsh Highland Sub. 

 

The full details for the hill are: 

Group:  Craig Berwyn

Name:  Cerrig Duon

OS 1:50,000 map:  125

Summit Height:  549.3m (LIDAR)

Summit Grid Reference:  SJ 12833 38497 (LIDAR)

Bwlch Height:  540.0m (LIDAR)

Bwlch Grid Reference:  SJ 12785 38809 (LIDAR)   

Drop:  9.3m (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 (September 2023)