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

Grindle (SO 430 926) 

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 initially conducted by Aled Williams and subsequently by Myrddyn Phillips.                                                                                                             

LIDAR image of Grindle (SO 430 926)

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 Grindle, and it is adjoined to the Stiperstones group of hills, which are situated in the county of Shropshire close to the Welsh border, and it is positioned with minor roads to its north and west, and the B4577 and A49 roads to its east, and has the town of Church Stretton towards the east north-east.

When the 1^st edition of the The Fours was published by Europeaklist in December 2013, this hill was listed with an estimated c 53m of drop, with a 459m summit height positioned at SO 430 926 based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and an estimated c 406m col height, based on interpolation of 5m contouring between 405m – 410m. 

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

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 listed with a 460.2m summit height, based on a Trimble GeoXH 6000 survey.

However, it was not until LIDAR became available that the details produced by the Trimble GeoXH 6000 survey 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 Grindle (SO 430 926)

LIDAR analysis gives the highest ground on this hill as 460.5m positioned at SO 43009 92663, and this is being prioritised over the result produced by the Trimble GeoXH 6000, 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 460.5m and this was derived from LIDAR analysis, this position is adjacent to where the 459m spot height appears on the Ordnance Survey 1:25,000 Explorer map and is 1.5m higher than it and importantly signifies contemporary Ordnance Surveys maps are missing an uppermost 460m ring contour. 

 

The full details for the hill are:

Group:  Stiperstones

Name:  Grindle

OS 1:50,000 map:  137

Summit Height (New Height):  460.5m (LIDAR)

Summit Grid Reference:  SO 43009 92663 (LIDAR)

Col Height:  406.6m (LIDAR)

Col Grid Reference:  SO 42581 92764 (LIDAR)

Drop:  53.9m (LIDAR)

 

Myrddyn Phillips and Aled Williams (December 2023)