Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

Ochr Llygnant (SN 796 917) – Welsh Highland P15 reclassified to Welsh Highland Sub 

There has been a reclassification 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 Ochr Llygnant (SN 796 917)

The criteria for the list that this reclassification 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 Ochr Llygnant and it is adjoined to the Pumlumon 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 north-east and its south south-west, the B4518 road to its east and the A44 road to its south, and has the village of Penffordd-las (Staylittle) towards the 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 included as a Welsh Highland P15 and listed with 15m of drop, based on a 49½ft/15.1m basic levelling survey conducted by Myrddyn Phillips on the 03.10.05.

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 reclassification of this hill to Welsh Highland Sub status is due to LIDAR analysis, resulting in a 550.4m summit height and a 536.0m bwlch height, with these values giving this hill 14.4m of drop, which is insufficient for it to be classified as a Welsh Highland P15. 

 

The full details for the hill are: 

Group:  Pumlumon

Name:  Ochr Llygnant

OS 1:50,000 map:  135

Summit Height:  550.4m (LIDAR)

Summit Grid Reference:  SN 79677 91711 (LIDAR)

Bwlch Height:  536.0m (LIDAR)

Bwlch Grid Reference:  SN 80023 91716 & SN 80022 91736 (LIDAR)   

Drop:  14.4m (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 (October 2023)