Mapping Mountains – Summit Relocations – Y Pedwarau – The 400m Hills of Wales

Pt. 439.8m (SO 001 769) 

There has been a Summit Relocation to a hill that is listed in the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

LIDAR image of Pt. 439.8m (SO 001 769)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills; 500m Sub-Pedwarau, 500m Double Sub-Pedwarau, 400m Sub-Pedwarau, 390m Sub-Pedwarau and the 390m Double Sub-Pedwarau.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The hill is being listed under the point (Pt. 439.8m) notation, and it is adjoined to the Hirddywel group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B2), and it is positioned with a minor road to its north-west, south and east, and the B4518 road to its west, and has the town of Llanidloes towards the north-west.

When the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013, this hill was listed with 77m of drop, based on the 441m summit spot height positioned at SO 00110 76944 that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 364m bwlch spot height that appears 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.

LIDAR analysis gives the highest ground on this hill as 439.9m positioned at SO 00118 76956.  However, this is to what LIDAR indicates is disturbed ground at the base of a wind turbine 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 Pt. 439.8m (SO 001 769)

The height produced by LIDAR analysis to the natural summit of this hill is 439.8m and this is positioned at SO 00120 76949, 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 439.8m and this is positioned at SO 00120 76949.  This position is relatively close to where the spot height is positioned on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and is approximately seven metres south-eastward from the high point of the disturbed ground at the base of the wind turbine.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Hirddywel 

Name:  Pt. 439.8m 

OS 1:50,000 map:  136, 147

Summit Height:  439.8m (LIDAR) 

Summit Grid Reference (New Position):  SO 00120 76949 (LIDAR) 

Bwlch Height:  362.8m (LIDAR) 

Bwlch Grid Reference:  SO 00766 77420 (LIDAR) 

Drop:  77.0m (LIDAR)

 

Myrddyn Phillips and Aled Williams (November 2025)