Mapping Mountains – Hill Reclassifications – The Welsh P15s

 

Cae’r Lloi Mawr (SH 507 390) – 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 derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cae'r Lloi Mawr (SH 507 390)

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 Cae’r Lloi Mawr and this was derived from the Tithe map, and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with a minor road and the B4411 road to its west and the A497 road to its south, and has the town of Cricieth towards the south-west.

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the main list with an estimated c 15m of drop, based on the 122m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 107m bwlch height, based on interpolation of 5m contouring between 105m – 110m that appeared on the OS Maps website. 

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 121.4m summit height and a 106.6m bwlch height, with these values giving this hill 14.7m 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:  Moel Hebog 

Name:  Cae’r Lloi Mawr 

OS 1:50,000 map:  124

Summit Height:  121.4m (LIDAR)                                                           

Summit Grid Reference:  SH 50771 39098 (LIDAR) 

Bwlch Height:  106.6m (LIDAR) 

Bwlch Grid Reference:  SH 50865 39392 (LIDAR) 

Drop:  14.7m (LIDAR) 

 

Myrddyn Phillips (August 2024)