Mapping Mountains – Hill Reclassifications – The Welsh P15s

R’allt (SH 717 028) – Welsh P15 addition 

There has been an addition to the list of The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of R'allt (SH 717 028)

The criteria for the list that this addition applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is R’allt, and this was derived from the Tithe map, and it is adjoined to the Tarren y Gesail group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with the A493 road to its south and the A487 road to its east, and has the town of Machynlleth towards the south-east.

When the listing that became known as The Welsh P15s was being compiled, this hill was not included in the main P15 or Sub P14 list, as with an uppermost 210m ring contour and bwlch contouring between 200m – 210m that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, it was deemed not to have sufficient prominence to be listed. 

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 P15 status is due to LIDAR analysis, resulting in a 216.4m summit height and a 201.0m bwlch height, with these values giving this hill 15.4m 0f drop, which is sufficient for it to be classified as a Welsh P15. 

 

The full details for the hill are: 

Group:  Tarren y Gesail 

Name:  R’allt 

OS 1:50,000 map:  135

Summit Height:  216.4m (LIDAR)                                                           

Summit Grid Reference:  SH 71732 02845 & SH 71735 02846 (LIDAR)

Bwlch Height:  201.0m (LIDAR) 

Bwlch Grid Reference:  SH 71653 02894 (LIDAR) 

Drop:  15.4m (LIDAR) 

 

Myrddyn Phillips (June 2025)