Thursday, 1 January 2015

Mapping Mountains – Trimble Surveys – Pen Llŷn

28.12.14  Mynydd Carreg (SH 163 291)   

Having watched the sun set next to the dark outline of Ynys Enlli we descended Mynydd y Gwyddel and navigated our way to the track that leads to a parking area for Mynydd Carreg.

By now it was almost dark with the afterglow of colour lighting the sky up out to sea.  We left the car and walked up a field toward a gate which gave access toward the summit of Mynydd Carreg.

Up yonder somewhere in the dark is the summit of Mynydd Carreg
The outline of the stone structure placed on the summit became visible as we gained the little height that was needed to reach the top.  This structure, or the area beside it, is indicated as a viewpoint on Ordnance Survey maps.  As we reached it the coastal view gave a colour wash of deep blues merging with those of light blues and the oranges of a disappeared sun, all highlighted against the black of land.

The last light of day
We examined the ground immediately beside the stone structure and decided that the grass in the middle of it was higher.  As I set the Trimble up on the grass Mark headed toward a rocky outcrop and looked back, confirming in his estimation that the ground at the centre of the stone structure was higher.

The stone structure on the summit of Mynydd Carreg
The Trimble placement was not ideal as it was positioned in the centre of a stone walled dungeon with only a gap to walk through on its eastern side.  As it started struggling down toward its 0.1m accuracy when data can start to be logged, we considered if I should have placed it on top of the stone wall surrounding its present position and taken a measurement offset to the ground below.  I checked the Trimble and quickly pressed ‘Log’ and ran out of the structure and stood behind the wall.

Gathering data at the summit of Mynydd Carreg
The Trimble didn’t seem to enjoy being where it was as it occasionally screamed as the accuracy bounced back up from 0.1m.  I’ve found that when this happens the equipment still logs data and soon achieves its necessary accuracy once again.

By now Mark had descended to his car and left the headlights on for an indicator for our descent and once five minutes of data were collected I followed Aled down toward the gate and the parking area.

This proved an ideal hill to visit in the dark as it had very little ascent from where we parked the car, and although almost dark when we set off we had the last glimpse of light out to sea.

Survey Result:

Mynydd Carreg 

Summit Height:  99.2m (converted to OSGM15) (100m Twmpau reclassified to 30-99m Twmpau confirmed)

Summit Grid Reference:  SH 16371 29168

Drop:  c 46m 

Dominance:  46.58% (Lesser Dominant status confirmed)

For further details please consult the Trimble survey spreadsheet click {here}

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