Mapping Mountains – Trimble Surveys – Yr Eifl

03.10.18  Clip y Gylfinhir (SH 223 284)  

Clip y Gylfinhir (SH 223 284)

Clip y Gylfinhir was previously surveyed with the Trimble GeoXH 6000 on the 28^th December 2014, the resulting height proved substantially lower than the 270m spot height that appears on the Ordnance Survey 1:25,000 Explorer map, and as the Standard Deviation and Estimated Accuracies indicated the data set was not good, I wanted to re-visit and survey this hill’s summit ever since.  The opportunity to do so was now here as Aled and I had visited Mynydd Penarfynydd and Mynydd y Graig and it was only a short drive from these hills to the parking area at the base of Clip y Gylfinhir, and whilst surveying this hill Aled could visit the adjacent Mynydd y Rhiw, a hill he had not previously been up.

Clip y Gylfinhir thrusts upward and is coned in profile, it stands out even from afar as a pimple like addition to the southern slopes of its higher neighbour; Mynydd y Rhiw, and the hill has association with the Tylwyth Teg; the mythological fairy like creatures of Welsh folklore.

As Aled headed north toward the trig pillar atop Mynydd y Rhiw I left a friendly Shetland pony beside my car and as it nuzzled its head against the boot, and hoped that it would not attempt to eat my rear wiper blade whilst I was on the hill!

Aled on the summit of Mynydd y Rhiw

A paved road leads to the adjacent mast and radar station that now sits beside Clip y Gylfinhir, from this paved road the hill thrusts upward, with it being steep on all sides.  I followed the road to its end and slowly plodded up the steep rocky slopes toward its summit where an autumnal breeze met me as it blew in from the sea.

The previous time this hill was Trimbled I’d placed the equipment aligned with the highest rock, this time I wanted the Trimble to be elevated above its immediate surrounds and therefore placed it on top of my rucksack which acted as an improvised tripod, having measured the offset between its internal antenna and the ground below I pressed ‘Log’ and waited for ten minutes of data to be gathered and stored.

Gathering data at the summit of Clip y Gylfinhir

The Trimble set-up position at the summit of Clip y Gylfinhir

As the Trimble gathered data I sat below it watching Aled making good progress up the path to the summit of Mynydd y Rhiw, he was descending the hill as the Trimble continued beeping away gathering its 600 individual datum points, once data were stored I closed the equipment down, packed it away and headed down to the paved road and arrived back at the car no more than a minute or so before Aled did likewise.

Survey Result:

Clip y Gylfinhir

Summit Height:  267.8m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SH 22395 28472

Bwlch Height:  240.1m (converted to OSGM15) (from previous Trimble GeoXH 6000 survey)

Bwlch Grid Reference:  SH 22514 28524 (from previous Trimble GeoXH 6000 survey)

Drop:  27.7m

Dominance:  10.34%

For details on the first Trimble survey of Clip y Gylfinhir

For further details please consult the Trimble Survey Spreadsheet