Mapping Mountains – Hill Reclassifications – The Welsh P15s

March Mynydd Ucha (SO 097 282) – Welsh Sub-P15 deletion

There has been a deletion 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 March Mynydd Ucha (SO 097 282)

The criteria for the list that this deletion 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 now listed by is March Mynydd Ucha and this was derived from the Tithe map, and it is adjoined to the Mynydd Epynt group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned enclosed by minor roads, with the A470 road farther to its west and the A40 road farther to its south-west, and has the town of Aberhonddu (Brecon) towards the west.

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the P14 sub list with an estimated c 14m of drop, based on the 270m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and an estimated c 256m bwlch height, based on interpolation of 10m contouring between 250m – 260m. 

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 Sub-P15 status is due to LIDAR analysis, resulting in a 271.1m summit height and a 257.4m bwlch height, with these values giving this hill 13.7m 0f drop, which is insufficient for it to be classified as a Welsh Sub-P15. 

 

The full details for the hill are: 

Group:  Mynydd Epynt 

Name:  March Mynydd Ucha 

OS 1:50,000 map:  161

Summit Height:  271.1m (LIDAR)                                                           

Summit Grid Reference:  SO 09744 28233 (LIDAR) 

Bwlch Height:  257.4m (LIDAR) 

Bwlch Grid Reference:  SO 09741 28417 (LIDAR) 

Drop:  13.7m (LIDAR) 

 

Myrddyn Phillips (July 2024)