Mapping Mountains – Summit Relocations – The Welsh P15s

Y Foel (SN 730 992) 

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 Y Foel (SN 730 992)

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 now listed by is Y Foel, and this was derived from the Tithe map, and it is adjoined to the Banc Llechwedd Mawr group of hills, which are situated in the north-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the A487 road to its north-west and minor roads to its south and east, and has the town of Machynlleth towards the north-east.

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 143m summit spot height positioned at SN 72970 99159 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 128m bwlch height, based on interpolation of 10m contouring between 120m – 130m. 

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 Y Foel (SN 730 992)

The height produced by LIDAR analysis to the summit of this hill is 143.8m and is positioned at SN 73037 99236, whilst LIDAR gives the highest ground adjacent to where the 143m spot height appeared as 143.5m positioned at SN 72974 99157, 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 high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, 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 or covered reservoir that is considered a relatively recent man-made construct, or the de-twinning of a summit, 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 143.8m and is positioned at SN 73037 99236, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, but was given a 142m spot height on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, and is approximately 77 metres north-eastward from where the highest ground adjacent to the 143m spot height appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

 

The full details for the hill are: 

Group:  Banc Llechwedd Mawr 

Name:  Y Foel 

OS 1:50,000 map:  135

Summit Height:  143.8m (LIDAR)                                                           

Summit Grid Reference (New Position):  SN 73037 99236 (LIDAR)                                                  

Bwlch Height:  129.1m (LIDAR) 

Bwlch Grid Reference:  SN 73017 99102 (LIDAR) 

Drop:  14.7m (LIDAR) 

 

Myrddyn Phillips (June 2025)