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

 

Low Fell (NY 135 222) 

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 by Joe Nuttall who produced a summit analysis programme using LIDAR, and then by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Low Fell (NY 135 222)

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 listing of The Fours are three categories of sub hills, with this hill being included in the 400m Sub-Four category, the criteria for which are all English 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 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 Low Fell, and it is adjoined to the Great Gable group of hills, which are situated in the Lake District (Region 34, Section 34B: The Central and Western Fells), and it is positioned with the A5086 road to its north-west, a minor road to its south and the B5289 road to its north-east, and has the small community of Brackenthwaite towards the east.

When the 2^nd edition of the The Fours – The 400m Hills of England was published by Mapping Mountains Publications in April 2018, this hill was not included in the accompanying sub list, as it was considered not to meet the criteria used for this sub category. 

During the updating of this list for the 2^nd edition this hill was noted and listed with an estimated c 13m of drop, based on the 412m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 399m col height based on interpolation of 10m contouring between 390m – 400m. 

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 this hill a summit height of 417.1m positioned at NY 13598 22260 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, this hill’s new listed summit height is 417.1m and this was derived from LIDAR analysis, this is 5.1m higher than its previously listed height of 412m which appears as a spot height on the Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  Great Gable

Name:  Low Fell

OS 1:50,000 map:  89

Summit Height (New Height):  417.1m (LIDAR)

Summit Grid Reference:  NY 13598 22260 (LIDAR)

Col Height:  395.5m (LIDAR)

Col Grid Reference:  NY 13659 22371 (LIDAR)

Drop:  21.6m (LIDAR)

 

Our thanks to Ronnie Bowron for bringing the details of this hill to our attention

Myrddyn Phillips and Aled Williams (August 2021)