Mapping Mountains – Summit Relocations – The Welsh P15s

 

Cae Bryn Celli Wen (SH 513 701) 

There has been a Summit Relocation to a hill that is listed in the 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 Bryn Celli Wen (SH 513 701)

The criteria for the list that this summit relocation 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 Bryn Celli Wen 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 A5 and A55 roads to its north, minor roads to its north-west and south-west and the A4080 road to its east, and has the village of Llanfair Pwllgwyngyll towards the north-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 17m of drop, based on an estimated c 51m summit height positioned at SH 51467 70268 and a 34m bwlch height based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 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. 

LIDAR summit image of Cae Bryn Celli Wen

The summit height produced by LIDAR analysis is 51.3m and is positioned at SH 51314 70143, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are: 

The term Summit Relocations applies when the hill’s high point is found to be positioned; in a different field, to a different feature such as in a conifer plantation, placed within a different map contour, to a different point where a number of potential summit positions are within close proximity, or when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist. 

Therefore, the summit height produced by LIDAR analysis is 51.3m and this is positioned at SH 51314 70143, this position is not given a spot height on contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps, and is approximately 150 metres south-westward from where the previously listed summit is positioned. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Cae Bryn Celli Wen 

OS 1:50,000 map:  114, 115

Summit Height:  51.3m (LIDAR) 

Summit Grid Reference (New Position):  SH 51314 70143 (LIDAR) 

Bwlch Height:  33.3m (LIDAR) 

Bwlch Grid Reference:  SH 51742 69854 (LIDAR) 

Drop:  18.0m (LIDAR) 

 

Myrddyn Phillips (May 2021)