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

Hergan (SO 262 853) 

There has been confirmation of a Summit Relocation to a hill that is 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 initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

LIDAR image of Hergan (SO 262 853)

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 are three categories of sub hills; the 400m Sub-Fours, the 390m Sub-Fours and the 390m Double Sub-Fours.  The list is co-authored by Myrddyn Phillips and Aled Williams and the 2^nd edition of the booklet containing this list was published by Mapping Mountains Publications on the 24^th April 2018.

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

The name the hill is listed by is Hergan, and it is adjoined to the Cilfaesty group of hills, which are situated in the county of Shropshire close to the Welsh border, and it is positioned encircled by minor roads, with the B4368 road farther to its south and the A488 road farther to its east, and has the town of Clun towards the south-east.

When the 1^st edition of the The Fours was published by Europeaklist in December 2013, this hill was listed with 50m of drop with a 409m summit height positioned at SO 263 853, and it was this position that was also given for the summit of this hill when the 2^nd edition of the The Fours – The 400m Hills of England was published by Mapping Mountains Publications in April 2018. 

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 409.0m positioned at SO 26308 85354.  However, this is a part of a sunken water tank 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 Hergan (SO 262 853)

The height produced by LIDAR analysis to the natural summit of this hill is 408.9m positioned at SO 26298 85342 and SO 26297 85345, and this position in relation to the sunken water tank comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to when the high point is positioned in a different field, to a different feature such as a conifer plantation, within a different map contour, a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit 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 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 408.9m and this is positioned at SO 26298 85342 and SO 26297 85345.  This position is given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 12 metres south-westward from the high point of the sunken water tank.

 

The full details for the hill are:

Group:  Cilfaesty

Name:  Hergan

OS 1:50,000 map:  137

Summit Height:  408.9m (LIDAR)

Summit Grid Reference (New Position):  SO 26298 85342 & SO 26297 85345 (LIDAR)

Col Height:  358.5m (LIDAR)

Col Grid Reference:  SO 26112 85472 (LIDAR)

Drop:  50.4m (LIDAR)

 

Myrddyn Phillips and Aled Williams (November 2023)