Friday, 14 August 2015

Mapping Mountains – Significant Height Revisions – 300m Twmpau

Coed y Gaer (SO 004 843)

This is the fourth post under the heading of Significant Height Revisions, and the following details are retrospective as the Trimble survey that resulted in this height revision was conducted on 9th February 2014.

The fourth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the Pegwn Mawr range of hills to the east of Llanidloes in the company Mark Trengove on a particularly wet and cold day.

The hill is listed as a Hump as well as in the height band of 300m Twmpau hills and can be accessed from a minor lane to the south; it overlooks the A470 and the Afon Hafren (River Severn) to its north-west.

The name of the hill is Coed y Gaer.  The height given the hill on current Ordnance Survey maps is 362m, with the height resulting from the survey with the Trimble being 359.9m.  This is not a dramatic height revision but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

The full details for the hill are:

Cardinal Hill:  Pegwn Mawr

Summit Height (New Height):  359.9m (converted to OSGM15)

Name:  Coed y Gaer

OS 1:50,000 map:  136

Summit Grid Reference:  SO 00488 84392
Drop:  121.7m

Gathering data with the Trimble GeoXH 6000 from the summit of Coed y Gaer

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (February 2014)

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