Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

Hen Gerrig (SH 950 187) – Welsh Highland Sub addition 

There has been an addition 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 Hen Gerrig (SH 950 187)

The criteria for the list that this addition 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 Hen Gerrig and it is adjoined to the Esgeiriau Gwynion group of hills, which are situated in the southern part of North Wales (Region A, Sub-Region A3), and it is positioned with the B4343 road to its north-east, minor roads to its west and south south-east and the A458 road to its south, and has the village of Llanwddyn towards the east.

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 9m of drop, based on a 518m summit height taken from the 1698ft (517.6m) height that appears on the Ordnance Survey series of Six-Inch maps, and an estimated c 509m bwlch height, based on interpolation of 5m contouring that appeared online.

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 addition of this hill to Welsh Highland Sub status is due to LIDAR analysis, resulting in a 518.1m summit height and a 507.9m bwlch height, with these values giving this hill 10.2m of drop, which is sufficient for it to be classified as a Welsh Highland Sub.

The full details for the hill are: 

Group:  Esgeiriau Gwynion

Name:  Hen Gerrig

OS 1:50,000 map:  125

Summit Height:  518.1m (LIDAR)

Summit Grid Reference:  SH 95070 18770 (LIDAR)

Bwlch Height:  507.9m (LIDAR)

Bwlch Grid Reference:  SH 95012 18806 (LIDAR)   

Drop:  10.2m (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)