Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

Trawsallt (SN 782 701) – 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 Trawsallt (SN 782 701)

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 Aled Williams and Myrddyn Phillips

The name the hill is listed by is Trawsallt and it is adjoined to the Carn yr Hyrddod 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 and the B4574 road to its north, the B4343 road to its west and a minor road to its south, and has the village of Pont-rhyd-y-groes towards the north-west.

When the initial P10 sub list was completed in June 2020 this hill was listed with an estimated c 7m of drop, based on the 564m summit spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and an estimated c 557m bwlch height, based on interpolation of 5m contouring that appeared on online mapping. 

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 addition of this hill to Welsh Highland Sub status is due to LIDAR analysis, resulting in a 564.5m summit height and a 552.8m bwlch height, with these values giving this hill 11.7m of drop, which is sufficient for it to be classified as a Welsh Highland Sub. 

 

The full details for the hill are: 

Group:  Carn yr Hyrddod

Name:  Trawsallt

OS 1:50,000 map:  135, 147

Summit Height:  564.5m (LIDAR)

Summit Grid Reference:  SN 78298 70193 (LIDAR)

Bwlch Height:  552.8m (LIDAR)

Bwlch Grid Reference:  SN 78147 70153 (LIDAR)   

Drop:  11.7m (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 (December 2023)