Sunday, 18 March 2018

Mapping Mountains – Significant Height Revisions – Tumps

Wapley Hill (SO 347 624)

There has been a Significant Height Revision to a hill that is listed in the Tumps.  This height revision was initiated by a survey with the Trimble GeoXH 6000 which took place on the 15th February 2018 in good conditions with clear visibility, albeit quite chilly.

The name of the hill is Wapley Hill and it is situated in Region 38 the Welsh Borders and in Section 38B West Gloucestershire, Hereford and Worcester.  The hill is positioned above the B 4362 road which is to its north, and has the town of Llanandras (Presteigne) towards its north-west and the village of Shobdon towards its east.

Wapley Hill (SO 347 624)

All of the upper part of the hill except for its northern section is a part of designated open access land, and although much of this upper section is forested there are a series of way-marked footpaths leading to its summit, which comprises an impressive Iron Age hill fort.

Prior to the survey with the Trimble GeoXH 6000 this hill was listed with a 329m summit height based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map.  The high point of the hill positioned on one of the ancient embankments that form a series of five defences, this embankment has a modern constructed entrance carved through it, and either side of this, to its immediate north, and its immediate south, are high points, each vying for the accolade of this hill’s summit position, with the northern one having been Abney levelled by numerous people as being slightly higher.

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

Extract from the Ordnance Survey Interactive Coverage map hosted on the Geograph website

These two high points were surveyed with the Trimble GeoXH 6000, the results are:

Northerly high point:  332.668m (converted to OSGM15) at SO 34754 62456

Southerly high point:  332.774m (converted to OSGM15) at SO 34749 62440 

The Trimble GeoXH 6000 gathering data at the northerly high point of Wapley Hill

The Trimble GeoXH 6000 gathering data at the southerly high point of Wapley Hill

The 332.8m (converted to OSGM15) summit height produced by the Trimble GeoXH 6000 is 3.8m higher than the previously listed height of 329m, which was based on the Ordnance Survey spot height that appears on the 1:25,000 Explorer map and which is positioned on the downward slope of the summit embankment, 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 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.  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 southerly summit of this hill is easily identified and consists of grass on the path that follows the higher of the embankments that form this ancient hill fort, it has steep ground either side of it, whilst the northerly summit is positioned near the base of a small oak tree and which is beside the narrow path that follows the continuation of the same higher embankment.

Therefore this hill’s new summit height is 332.8m (converted to OSGM15), which is 3.8m higher than its previously listed height which came from the 329m spot height on contemporary Ordnance Survey 1:25,000 Explorer maps.

The full details for the hill are:

Group:  Fforest Glud

Summit Height (New Height):  332.8m (converted to OSGM15)

Name:  Wapley Hill

OS 1:50,000 map:  137, 148, 149

Summit Grid Reference:  SO 34749 62440
Drop:  160.2m (Trimble summit and LIDAR col)

Myrddyn Phillips (March 2018)

No comments: