Mapping Mountains – Summit Relocations – The Fours – The 400m Hills of England

 

Disgwylfa (SO 172 841) 

There has been a Summit Relocation to a hill listed in the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Disgwylfa (SO 172 841)

The criteria for the list that this summit relocation applies to are:

The Fours – The 400m Hills of England - English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list is a sub list entitled the Sub-Fours, the criteria for which are all English hills at or above 400m and below 500m in height that have 15m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available to download in Google Doc format from the Mapping Mountains site.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The name the hill is now listed by is Disgwylfa, and this was derived from the Ordnance Survey One-Inch ‘Old Series’ map, and it is adjoined to the Cilfaesty group of hills, which are situated adjoined to the Welsh border, and it is positioned with the B4368 road to its north, and minor roads to its west and east, and has the town of Ceri towards the north north-west.

When the Introduction to the first group of hills for the updated and revised listing of the The Fours – The 400m Hills of England was published by Mapping Mountains on the 10^th September 2022, it was announced that the accompanying sub lists were being revised with the two 390m categories dispensed with and the criteria and name of the 400m Sub-Fours revised.  The one accompanying sub list is now named the Sub-Fours with its criteria being all English hills 400m and above and below 500m in height that have 15m and more and below 30m of drop.

Prior to this revision this hill was listed with an estimated c 15m of drop, based on the 427m summit spot height positioned at SO 17503 84053 that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 412m col height, based on interpolation of 10m contouring between 410m – 420m. 

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 analysis gives the highest ground on this hill as 429.2m positioned at SO 17249 84185.  However, this is to the top of a raised track that forms a field boundary and protocols dictate that as this is deemed a relatively recent man-made construct such ground is discounted from the height of a hill. 

LIDAR summit image of Disgwylfa (SO 172 841)

The height produced by LIDAR analysis to the natural summit of this hill is 428.9m and this is positioned at SO 17246 84195, 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 428.9m and this is positioned at SO 17246 84195.  This position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 10 metres north north-westward from where the high point of the raised track that forms a field boundary is positioned and approximately 263 metres west north-westward from where the 427m spot height appears. 

 

The full details for the hill are:

Group:  Cilfaesty

Name:  Disgwylfa

OS 1:50,000 map:  136

Summit Height:  428.9m (LIDAR)

Summit Grid Reference (New Position):  SO 17246 84195 (LIDAR)

Col Height:  410.9m (LIDAR)

Col Grid Reference:  SO 17775 83941 (LIDAR)

Drop:  18.0m (LIDAR)

 

Myrddyn Phillips and Aled Williams (March 2026)