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

 

Pen y Rhaglan Wynt (SN 739 490) 

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 conducted by Myrddyn Phillips. 

LIDAR image of Pen y Rhaglan Wynt (SN 739 490)

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, with this hill being included in the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  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 name the hill is listed by is Pen y Rhaglan Wynt, and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north and south, and has the village of Llanddewibrefi towards the north-west. 

Extract from the Ordnance Survey 1:25,000 Explorer map

When the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013, this hill was listed with 26m of drop, based on the 423m summit spot height positioned at SN 73826 49110 that appears on the Ordnance Survey 1:25,000 Explorer map and the 397m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.  This hill was listed with an accompanying note stating; Second summit of same map height at SN 739 490.  This second 423m spot height appears on the Ordnance Survey 1:50,000 Explorer map and appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

Extract from the Ordnance Survey 1:50,000 Landranger 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 Pen y Rhaglan Wynt (SN 739 490)

LIDAR analysis gives the highest ground on this hill as 423.4m positioned at SN 73918 49040, as opposed to LIDAR giving 423.3m positioned at SN 73823 49117, 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 listing of a new twin summit or 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 height produced by LIDAR analysis to the summit of this hill is 423.4m and is positioned at SN 73918 49040.  This position is relatively close to where one of the 423m spot heights appears on the Ordnance Survey 1:50,000 Explorer map and appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and approximately 160 metres south-eastward from where the twin map heighted spot height appears on the Ordnance Survey 1:25,000 Explorer map, resulting in the de-twinning of this hill.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Esgair Wen 

Name:  Pen y Rhaglan Wynt 

OS 1:50,000 map:  146, 147

Summit Height:  423.4m (LIDAR) 

Summit Grid Reference (New Position):  SN 73918 49040 (LIDAR) 

Bwlch Height:  397.5m (LIDAR) 

Bwlch Grid Reference:  SN 73569 49497 (LIDAR) 

Drop:  26.0m (LIDAR)

 

Myrddyn Phillips and Aled Williams (June 2026)