Mapping Mountains – Hill Reclassifications – The Welsh P15s

 

Mynydd Deulyn (SH 754 605) – Welsh Sub-P15 reclassified to Welsh 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 derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Mynydd Deulyn (SH 754 605)

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 now listed by is Mynydd Deulyn, and this was derived from the Ordnance Survey series of Six-Inch maps, and it is adjoined to the Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned between Llyn Crafnant to its north-west and Llyn Geirionydd to its east, with the A5 road to its south, and the B5106 road, the Afon Conwy and the A470 road to its east, and has the village of Capel Curig towards the south-west and the town of Llanrwst towards the east.

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the accompanying sub list with an estimated c 14m of drop, based on the 336m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 322m bwlch height, based on interpolation of 10m contouring between 320m – 330m. 

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 from Welsh Sub-P15 status is due to LIDAR analysis, resulting in a 334.8m summit height and a 318.4m bwlch height, with these values giving this hill 16.4m 0f drop, which is sufficient for it to be classified as a Welsh P15. 

 

The full details for the hill are: 

Group:  Carnedd Llywelyn 

Name:  Mynydd Deulyn 

OS 1:50,000 map:  115

Summit Height:  334.8m (LIDAR)                                                           

Summit Grid Reference:  SH 75464 60544 (LIDAR)                                                  

Bwlch Height:  318.4m (LIDAR) 

Bwlch Grid Reference:  SH 75563 60655 (LIDAR) 

Drop:  16.4m (LIDAR) 

 

Myrddyn Phillips (June 2026)