Thursday, 21 June 2018

Mapping Mountains – Significant Height Revisions – Tumps

View Edge (SO 422 809)

There has been a Significant Height Revision to a hill that is listed in the Tumps, which was initiated by a survey with the Trimble GeoXH 6000 which took place on the 4th May 2018 in the company of Bob Kerr, with clear and calm conditions on the hill.

The name of the hill is View Edge and it is situated in Region 38 the Welsh Borders and in Section 38A Shropshire.  The hill is positioned between a number of roads with the B 4367 to its west, the B 4368 to its north and the A 49 to its east, and has the small town of Craven Arms towards its north north-east.

View Edge (SO 422 809)

As the hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so a public footpath from the south accesses the wood close to where the summit is situated.

Prior to the survey with the Trimble GeoXH 6000 this hill was listed with a 321m summit height which is based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map.  Otherwise I have found no other summit height on any scaled Ordnance Survey map, with only the Six-Inch map published in 1903 giving a 1045ft (318.5m) height to the east of the summit.

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

Extract from the Ordnance Survey Six-Inch map published in 1903

The summit of the hill is positioned in mixed woodland which is not ideal for satellite coverage, and because of this a 15 minute data set was taken.  However, once data were processed the standard deviation was 1.0m and the estimated accuracies were 0.5 – 1m: 25.65%.

The 324.1m (converted to OSGM15) summit height produced by the Trimble GeoXH 6000 is 3.1m higher than the previously listed height of 321m, which was based on the summit spot height on contemporary Ordnance Survey 1:25,000 maps, and therefore this new height 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 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, and also hill’s that do not possess a summit spot height and whose estimated summit height has a 2m or more discrepancy when compared to data produced either by the Trimble or by 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.

The summit of this hill is easily identified and consists of ground near the base of a tree, which is approximately 20 metres from a fence and an adjacent closely cropped grazing field.  On the day that the survey took place the wood was resplendent with bluebells.

The Trimble GeoXH 6000 gathering data at the summit of View Edge

Therefore this hill’s new summit height is 324.1m (converted to OSGM15), which is 3.1m higher than its previously listed height which was derived from the 321m summit spot height on the Ordnance Survey 1:25,000 Explorer map.

The full details for the hill are:

Group:  Beacon Hill

Summit Height (New Height):  324.1m (converted to OSGM15)

Name:  View Edge

OS 1:50,000 map:  137

Summit Grid Reference:  SO 42278 80988
Drop:  c 170m

Myrddyn Phillips (June 2018)

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