Mapping Mountains – Significant Height Revisions – The Fours – The 400m Hills of England

 

Sourton Tors (SX 543 898) 

There has been a Significant Height Revision 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 conducted by Myrddyn Phillips. 

LIDAR image of Sourton Tors (SX 543 898)

The criteria for the list that this height revision 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 listed by is Sourton Tors, and it is adjoined to the High Willhays group of hills, which are situated in the south-west of England, and it is positioned with the A386 road to its west, and has the town of Oakhampton towards the north-east.

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 17m of drop, based on the 440m summit spot height adjoined to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 423m col spot height that 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 1:25,000 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 Sourton Tors (SX 543 898)

LIDAR analysis gives the summit height of this hill as 442.9m positioned at SX 54331 89827 and when compared to its originally listed height this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey, Harvey or other interactive map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 442.9m and this was derived from LIDAR analysis, this is 2.9m higher than the originally listed 440m summit height that appears adjoined to a triangulation pillar on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  High Willhays

Name:  Sourton Tors

OS 1:50,000 map:  191

Summit Height (New Height):  442.9m (LIDAR)

Summit Grid Reference:  SX 54331 89827 (LIDAR)

Col Height:  423.9m (LIDAR)

Col Grid Reference:  SX 54641 89624 (LIDAR)

Drop:  18.9m (LIDAR)

 

Myrddyn Phillips and Aled Williams (August 2026)