Mapping Mountains – Trimble Surveys – Glyder Fawr

17.08.24  Elidir Fach (SH 603 613) 

A chilly early morning walk through the upper portion of Chwarel Dinorwig brought me onto the open hillside beneath the summit of Elidir Fach.  Shortly after the release of new Welsh LIDAR data in early 2023, this hill was deleted from the Subs of The Welsh Highlands list due to the resultant 9.8m drop failing the 10.0m qualification threshold.  Ever since, this hill has been high on the priority list for an accurate Trimble GeoXH 6000 survey.

The first survey for summit position and height.  Photo: Aled Williams.

The summit of Elidir Fach consists of a shelter-cairn built around small outcrops of rock, one of which being a contender for the high point of the hill.  Beside the cairn on the north side is another contender, a small outcropping rock, seemingly at the central point of the summit dome.  A third contender is a larger boulder found to the south of the cairn among a collection of weathered outcrops.  I checked each out from various angles with an Abney level, but struggled to definitively rule out one of the others.  There was only one thing for it – three summit surveys were necessary!

The second survey for summit position and height.  Photo: Aled Williams.

I thankfully had the summit all to myself for the duration of the surveying, free of distraction and interruption.  This proved unusual as over the next hour no fewer than eight people would come and go from this minor top.

The summit area with the Trimble at the third summit contender.  Photo: Aled Williams.

The next phase was to survey the bwlch, which I knew in advance would entail two sets of measurements given that LIDAR data gave two positions of equal height.  I was however glad of LIDAR positioning, as the flat expanse of the bwlch made judging the low point by eye extremely difficult.

The bwlch backed by the upper slope of Elidir Fawr.  Photo: Aled Williams.

As data collected on the bwlch, I looked upon the continuation of the Eryri peaks either side of it with the pastoral lands of Môn stretching on beyond the Menai.  I felt glad to be born a Welshman!  I packed up the equipment and headed back down to the car.  It had been an enjoyable morning on the hill and I was looking forward to know the outcome of the surveying work.

Surveying one of the two options for the critical bwlch.  Photo: Aled Williams.

Surveying one of the two options for the critical bwlch.  Photo: Aled Williams.

 

Aled Williams (August 2024)

 

Survey Result: 

 

Elidir Fach

Summit Height:  794.2m (converted to OSGM15)

Summit Grid Reference:  SH 60377 61341

Bwlch Height:  784.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 60556 61279

Drop:  10.0m (Welsh Highland Sub reinstatement)

Dominance:  1.26%

 

 

For further details please consult the Trimble Survey Spreadsheet