Monday, 26 October 2015

Mapping Mountains – Significant Height Revisions – Y Pedwarau

Cerrig y Gordref (SH 929 428)

This is the twenty second 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 the 2nd October 2015.

The twenty second major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the Arennig hills between Y Bala to the south and Cerrigydrudion to the north north-east.  The hill was surveyed in the company of Aled Williams who had suggested the walk.

The hill is listed in the Y Pedwarau (Europeaklist May 2013) as a 400m Sub-Pedwar with 28m of drop based on the 497m spot height that appears on Ordnance Survey maps at SH 93066 42836 and the 469m spot height at the bwlch that is positioned at SH 93210 42714.  However, the summit area of the hill also has a 495m spot height at SH 92974 42817 that appears on the Ordnance Survey enlarged mapping on the Geograph website.

The hill can be combined with its neighbours of Y Gesail and Garnedd Fawr but the best way to take the hill in is during an extended two car walk, giving the opportunity to visit many of the hills that are situated close to Foel Goch, which is the highest point in this compact group of hills.

The name of the hill is Cerrig y Gordref and prior to the survey with the Trimble GeoXH 6000 the height of the hill was listed as 497m.  The high point of the land where the 497m and the 495m spot heights appear on the ground were each surveyed with the Trimble GeoXH 6000 with the following results:

497m spot height:  490.8m (converted to OSGM15) at SH 93066 42834

495m spot height:  494.6m (converted to OSGM15) at SH 92971 42820

The actual height of the land where the 497m spot height is positioned is significantly lower than the current map suggests, and this is probably a typo on the part of the Ordnance Survey.  Although the actual height of the land where the 495m spot height is positioned is only 0.4m different to the map height, there is a significant height difference when compared to this hill’s previously listed summit height.

Therefore this hill’s new summit height is 494.6m (converted to OSGM15) which is 2.4m lower than its previously listed height of 497m which was based on the current Ordnance Survey spot height which is probably a typo as the land at this point is only 490.8m (converted to OSGM15) high.

The full details for the hill are:

Cardinal Hill:  Foel Goch

Summit Height (New Height):  494.6m (converted to OSGM15)

Name:  Cerrig y Gordref

OS 1:50,000 map:  125

Summit Grid Reference:  SH 92971 42820 
Drop:  26.0

Gathering data from the summit of Cerrig y Gordref which resulted in this hill's significant height revision

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

Myrddyn Phillips and Aled Williams (October 2015)

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