Mapping Mountains – Significant Height Revisions – The 500-Metre Tops of England and Wales – Deweys

Yarnspath Law (NT 887 135) 

There has been a Significant Height Revision to a hill that is listed in the The 500-Metre Tops of England and Wales, 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 Yarnspath Law (NT 887 135)

The criteria for the list that this height revision applies to are:

The 500-Metre Tops of England and Wales are affectionately known after their hill list compiler; Michael Dewey.  This list mixes metric and imperial height in its criteria to bookend up to the 2000ft height band and takes in all hills in England, Isle of Man and Wales that are 500m and above and below 2000ft (609.6m) in height that have 30m minimum drop. 

Mountain tables by Michael Dewey

Michael Dewey died on the 5^th November 2022.  His wife; Gillian wished for this list to be carried on and made provision for it to be co-authored by Myrddyn Phillips.  Michael will always be the compiler and originator, it’s just that he’s now got a co-author to safeguard this list and carry it on.

The name the hill is listed by is Yarnspath Law and it is adjoined to the The Cheviot group of hills, which are situated in the north-eastern part of England, and it is positioned with the A68 road to its south-west and the A697 road to its east, and has the town of Wooler towards the north-east.

Extract from the Ordnance Survey 1:50,000 Landranger map

When the original list of Deweys appeared in the Mountain tables book published by Constable in 1995, this hill was listed with a summit height of 543m, based on the spot height positioned at NT 88409 13238 that appears on the Ordnance Survey 1:50,000 Landranger and 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 summit image of Yarnspath Law (NT 887 135)

LIDAR analysis gives the summit of this hill as 540.7m positioned at NT 88720 13549, and when compared to its originally listed summit height of 543m 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 540.7m and this was derived from LIDAR analysis, this is 2.3m lower than the originally listed summit height of 543m, which was based on the spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  The Cheviot

Name:  Yarnspath Law

OS 1:50,000 map:  80

Summit Height (New Height):  540.7m (LIDAR)

Summit Grid Reference:  NT 88720 13549 (LIDAR)  

Col Height:  506.4m (LIDAR)

Col Grid Reference:  NT 89366 13893 (LIDAR)

Drop:  34.3m (LIDAR)

 

My thanks to Ronnie Bowron for suggesting to LIDAR this hill with the prospect of its summit relocation. 

Myrddyn Phillips (December 2025)