Mapping Mountains – Summit Relocations – The Fours – The 400m Hills of England

 

Grayrigg Forest (NY 590 003) 

There has been a Summit Relocation 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 Grayrigg Forest (NY 590 003)

The criteria for the list that this summit relocation applies to 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, with this hill being listed 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 Grayrigg Forest, and it is adjoined to the Grayrigg Forest group of hills, which are situated in the far eastern fells of the Lake District, and it is positioned with a minor road to its west and the A685 road and the M6 motorway to its east, and has the town of Kendal towards the 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 listed with 23m of drop, based on the 439m twin summit map spot heights positioned at NY 59233 00047 that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and positioned at NY 59090 00316 that appears on the Ordnance Survey 1:25,000 Explorer map and the 416m col spot height that appears on the Ordnance Survey 1:25,000 Explorer map, with the summit positioned at NY 592 000 prioritised.

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 image of the 438.8m summit positioned at NY 59082 00314

LIDAR image of the 438.2m summit positioned at NY 59230 00041

LIDAR analysis gives the highest ground on this hill as 438.8m positioned at NY 59082 00314, as opposed to 438.2m positioned at NY 59230 00041 and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to when the high point is positioned in a different field, to a different feature such as a conifer plantation, within a different map contour, a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the summit height produced by LIDAR analysis is 438.8m and this is positioned at NY 59082 00314.  This position is given a spot height on the contemporary Ordnance Survey 1:25,000 Explorer map and was the non-prioritised summit listed in the Mapping Mountains Publications booklet published on the 24^th April 2018, and is approximately 300 metres north-westward from where the previously listed prioritised summit is positioned. 

 

The full details for the hill are:

Group:  Grayrigg Forest

Name:  Grayrigg Forest

OS 1:50,000 map:  91

Summit Height:  438.8m (LIDAR)

Summit Grid Reference (New Position):  NY 59082 00314 (LIDAR)

Col Height:  417.1m (LIDAR)

Col Grid Reference:  SD 59345 99922 (LIDAR)

Drop:  21.6m (LIDAR)

 

Myrddyn Phillips and Aled Williams (January 2023)