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

 

Crook (SD 664 935) 

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 Crook (SD 664 935)

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 Crook, and it is adjoined to the The Calf group of hills, which are situated in the Howgill Fells (Region 35, Section 35A: The Northern Pennines), and it is positioned with the B6257 road to its west, the A684 road to its south and the A683 road to its east, and has the town of Sedbergh towards the south south-west.

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.

 

Extract from the Ordnance Survey 1:25,000 Explorer map

During the updating of this list for the 2^nd edition this hill was noted and listed with an estimated c 17m of drop, based on the 462m summit spot height that appears on the Harvey 1:25,000 Superwalker map to the Howgill Fells and an estimated c 445m col height based on interpolation of 10m contouring between 440m – 450m that appear on the Ordnance Survey 1:25,000 Explorer map.

 

Extract from the Harvey 1:25,000 Superwalker map to the Howgill Fells

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 Crook

LIDAR analysis gives this hill a summit height of 464.7m positioned at SD 66458 93550 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 464.7m and this was derived from LIDAR analysis, this is 2.7m higher than its previously listed height of 462m which appears as a spot height on the Harvey 1:25,000 Superwalker map to the Howgill Fells. 

 

The full details for the hill are:

Group:  The Calf

Name:  Crook

OS 1:50,000 map:  98

Summit Height (New Height):  464.7m (LIDAR)

Summit Grid Reference:  SD 66458 93550 (LIDAR)

Col Height:  444.4m (LIDAR)

Col Grid Reference:  SD 66410 93726 (LIDAR)

Drop:  20.3m (LIDAR)

 

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

Myrddyn Phillips and Aled Williams (September 2021)