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

Lag Bank (SD 249 942) 

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 Lag Bank (SD 249 942)

The criteria for the list this height revision affects 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-Four category, the 390m Sub-Four category and the 390m Double Sub-Four category.  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 Lag Bank, and it is adjoined to the The Old Man of Coniston group of hills, which are situated in the southern fells of the Lake District, and it is positioned with a minor road to its north-west and the A593 road to its south-east, and has the village of Coniston towards the north-east.

When the 2^nd edition of the The Fours – The 400m Hills of England was published by Mapping Mountains Publications in April 2018, the height of this hill was listed as 411m with its summit positioned at SD 250 943, based on the spot height positioned at SD 25078 94336 which 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 analysis gives the highest ground on this hill as 411.2m positioned at SD 24996 94270, as opposed to 410.4m positioned at SD 25083 94336 and 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 or Harvey 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 to the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 411.2m and this was derived from LIDAR analysis, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is 11.2m higher than the uppermost 400m ring contour that appears in this position. 

 

The full details for the hill are:

Group:  The Old Man of Coniston

Name:  Lag Bank

OS 1:50,000 map:  96

Summit Height (New Height):  411.2m (LIDAR)

Summit Grid Reference:  SD 24996 94270 (LIDAR)

Col Height:  380.85m (LIDAR)

Col Grid Reference:  SD 25214 94767 (LIDAR)

Drop:  30.3m (LIDAR)

 

Myrddyn Phillips and Aled Williams (December 2022)