Mapping Mountains – Hill Reclassifications – The Welsh P15s

Wylfa (SH 353 939) – Welsh P15 reclassified to Welsh Sub-P15

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

LIDAR image of Wylfa (SH 353 939)

The criteria for the list that this reclassification 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 Wylfa and this was derived from the Tithe map and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north, west and east and has a minor road and the A5025 road farther afield to its south-east, and has the village of Cemaes towards the east south-east. 

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the main P15 list with an estimated c 15m of drop, based on the 37m 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 22m bwlch height based on interpolation of 5m contouring between 20m – 25m that appear on the Ordnance Survey 1:25,000 Explorer map. 

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 reclassification of this hill to Welsh Sub-P15 status is due to LIDAR analysis, resulting in a 38.1m summit height and a 23.9m bwlch height, with these values giving this hill 14.2m of drop, which is insufficient for it to be included in the main list of The Welsh P15s. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Wylfa 

OS 1:50,000 map:  114

Summit Height:  38.1m (LIDAR)                                                           

Summit Grid Reference:  SH 35376 93925 (LIDAR) 

Bwlch Height:  23.9m (LIDAR) 

Bwlch Grid Reference:  SH 35428 93863 (LIDAR) 

Drop:  14.2m (LIDAR) 

 

Myrddyn Phillips (June 2021)