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

 

Dow Low (SK 094 680) 

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 conducted by Myrddyn Phillips. 

LIDAR image of Dow Low (SK 094 680)

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 reclassified from 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 Dow Low, and it is adjoined to the Axe Edge group of hills, which are situated in The Southern Pennines (Region 36), and it is positioned with the B5053 road to its west and the A515 road to its north-east, and has the town of Buxton towards the north-west.

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 included as a 400m Sub-Four and listed with an estimated c 29m of drop, based on an estimated c 426m summit height and an estimated c 397m col height, with both heights based on interpolation of 5m contouring that appeared on the OS Maps website. 

Extract from the OS Maps website

The prominence of this hill has been created from the quarrying activities of the Hindlow Quarry.  When it was initially included as a 400m Sub-Four, imagery on Google Maps and Google Earth was examined with the conclusion that the hill is solid and stable.

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 Dow Low (SK 094 680)

LIDAR analysis gives this hill a summit height of 430.1m positioned at SK 09419 68071 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 430.1m and this was derived from LIDAR analysis, this is 4.1m higher than its previously listed height of c 426m which was based on interpolation of 5m contouring that appeared on the OS Maps website. 

 

The full details for the hill are:

Group:  Axe Edge

Name:  Dow Low

OS 1:50,000 map:  119

Summit Height (New Height):  430.1m (LIDAR)

Summit Grid Reference:  SK 09419 68071 (LIDAR)

Col Height:  396.3m (LIDAR)

Col Grid Reference:  SK 09251 68164 (LIDAR)

Drop:  33.8m (LIDAR)

 

Myrddyn Phillips and Aled Williams (October 2022)