Tuesday, 26 June 2018

Mapping Mountains – Significant Height Revisions – The Fours


Black Hill (SX 761 786)

There has been a Significant Height Revision to a hill that is listed in The Fours initiated by LIDAR analysis conducted by Aled Williams.  The Fours is the title for the list of 400m hills of England and is co-authored by Myrddyn Phillips and Aled Williams with the 2nd edition of the booklet containing this list published by Mapping Mountains Publications on the 24.04.18.

The criteria for the list that this significant height revision affects are:

The Fours - English hills at and above 400m and below 500m in height that have a minimum 30m of drop.

The name of the hill is Black Hill and it is situated in Region 40; Cornwall and Devon, and is positioned overlooking the River Bovey to its north-east and between the A 382 road also to its north-east and the A 38 road to its south south-east, and has the village of Widecombe-in-the-Moor to its west south-west and the town of Bovey Tracey to its east.

As the hill is a part of designated open access land its summit can be approached from a number of directions, with the convenience of a minor road to the north giving access to a public footpath and a narrow path leading toward its summit.

Prior to LIDAR analysis this hill was listed with c 31m of drop based on the 412m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated col height of c 381m based on interpolation of col contouring between 380m – 390m.

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

The summit height produced by LIDAR analysis is 414.1m, this is not a dramatic height revision when compared to some revised heights, but it does come 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 by LIDAR analysis, 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 analysis of LIDAR.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these revisions.

Therefore, this hill’s new summit height is 414.1m and this was produced by LIDAR analysis, this is 2.1m higher than its previously listed height of 412m which appears as a spot height on the Ordnance Survey 1:25,000 Explorer map.


The full details for the hill are:

Cardinal Hill:  Broad Barrow

Summit Height (New Height):  414.1m (LIDAR)

Name:  Black Hill

OS 1:50,000 map:  191

Summit Grid Reference:  SX 76105 78646 (LIDAR) 
  
Drop:  33.1m (LIDAR)


Myrddyn Phillips and Aled Williams (June 2018)











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