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

 

Thirkelow Rocks (SK 049 691) 

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 Thirkelow Rocks (SK 049 691)

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; the 400m Sub-Fours, the 390m Sub-Fours and the 390m Double Sub-Fours.  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 Thirkelow Rocks, and it is adjoined to the Axe Edge group of hills, which are situated in the Peak District, and it is positioned with minor roads to its north-east and west, and the A53 road farther to its west, and has the town of Buxton towards the north.

When the 1^st edition of the The Fours was published by Europeaklist in December 2013, this hill was listed with an estimated c 451m summit height, based on interpolation of the slightly larger and northerly of two uppermost 450m contour rings that appear on the Ordnance Survey 1:25,000 Explorer map and which is positioned at SK 049 692, and it was this position that was also given for the summit of this hill when the 2^nd edition of the The Fours – The 400m Hills of England was published by Mapping Mountains Publications in April 2018. 

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 summit image of Thirkelow Rocks (SK 049 691)

LIDAR analysis gives the highest ground on this hill as 450.9m positioned at SK 04939 69143, as opposed to 450.7m positioned at SK 04922 69224, 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 450.9m and this is positioned at SK 04939 69143.  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 approximately 80 metres southward and positioned in a different map contour to where the previously listed summit was positioned.

 

The full details for the hill are:

Group:  Axe Edge

Name:  Thirkelow Rocks

OS 1:50,000 map:  119

Summit Height:  450.9m (LIDAR)

Summit Grid Reference (New Position):  SK 04939 69143 (LIDAR)

Col Height:  417.3m (LIDAR)

Col Grid Reference:  SK 04755 69364 (LIDAR)

Drop:  33.6m (LIDAR)

 

Myrddyn Phillips and Aled Williams (October 2023)