Thursday, 27 August 2015

Mapping Mountains – Significant Height Revisions – Yr Uchafion and 700m Sub-Twmpau

Llechog (SH 606 567) 

This is the tenth 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 September 2014.

The tenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Yr Wyddfa range in the heartland of Eryri on a beautiful sunny September day.

The hill can be accessed from the Llanberis Path which is one of the six main paths up Yr Wyddfa.  This path roughly follows the course of the railway line as it ascends the mountain from Llanberis, and the hill stands on a ridge that is seldom visited by the multitude of walkers who head toward the summit of Wales’ highest mountain.

The name of the hill is Llechog.  The height given the hill on current Ordnance Survey maps is 718m, with the height resulting from the survey with the Trimble being 720.0m (converted to OSGM15).  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.

Therefore this hill’s new summit height is 2.0m higher than its previously listed height which came from the 718m spot height on current Ordnance Survey maps.

The full details for the hill are:

Cardinal Hill:  Yr Wyddfa

Summit Height (New Height):  720.0m (converted to OSGM15)

Name:  Llechog

OS 1:50,000 map:  115

Summit Grid Reference:  SH 60613 56751
Drop:  28.0m

Gathering data from the summit of Llechog 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 (September 2014)

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