Mapping Mountains – Hill Reclassifications – The Welsh P15s

 

Melin Llanddyfnan (SH 483 786) – Welsh Sub-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 Melin Llanddyfnan (SH 483 786)

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 Melin Llanddyfnan and this was derived from online sources in combination with detail on 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-east, a minor road to its immediate north-west and south, the B5110 road farther to its north-west and the B5109 road to its south-east, and has the town of Llangefni towards the south-west. 

When the listing that became known as The Welsh P15s was being compiled, this hill was not included in the P14 sub list and was listed with an estimated c 13m of drop, based on an estimated c 86m summit height and an estimated c 73m bwlch height, with both heights based on interpolation of 5m contouring 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 addition of this hill to Welsh Sub-P15 status is due to LIDAR analysis, resulting in an 87.2m summit height and a 72.2m bwlch height, with these values giving this hill 14.9m 0f drop, which is sufficient for it to be classified as a Welsh Sub-P15. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Melin Llanddyfnan 

OS 1:50,000 map:  114, 115

Summit Height:  87.2m (LIDAR)                                                           

Summit Grid Reference:  SH 48371 78617 (LIDAR) 

Bwlch Height:  72.2m (LIDAR) 

Bwlch Grid Reference:  SH 48391 79121 (LIDAR) 

Drop:  14.9m (LIDAR) 

 

Myrddyn Phillips (October 2021)