Mapping Mountains – Trimble Surveys - Y Berwyn

15.12.13  Cyrniau (SJ 063 251) and Moel Dimoel (SJ 028 255)

Cyrniau (SJ 063 251) 

The first survey with the Trimble was a walk suggested by Mark Trengove, as he wanted to visit the Hump of Cyrniau and we both wanted to get to grips with Moel Dimoel, which had taken on a reputation as being ‘The Inaccessible Pedwar’ due to its forested summit and steeply guarded craggy profile.

A good parking area now exists above an old quarry on the outskirts of Llangynog.  This is part of the land now operated by the Revolution Bikepark team of enterprising entrepreneurs, who have bought the lease to part of the forest and spent a great deal of time manufacturing downhill mountain bike trails. 

The route to Cyrniau followed one of the forest tracks from this car park up on to open hillside where a short walk gained the summit.  This is crowned by a quart outcrop of rock and has views down the Tanat valley and across to the higher Berwyn.

The Trimble GeoXH on the summit of Cyrniau

Next stop was the bwlch which caused a bit of debate on where the surveying equipment should be placed.  The reason for this was a track that led on to one of the main forest tracks.  Should the equipment be placed on natural ground beside the track or on the track itself?  Eventually the decision was taken to place it on the track as this followed the hill to hill traverse.

Mark and a member of the Revolution Bikepark team with the Trimble on its Draper tripod at the bwlch of Cyrniau

After eleven minutes of data collection we descended to the car and drove further up the valley towards Pwlliago and started the walk up Moel Dimoel.  The weather forecast was not very promising for the afternoon as heavy showers and lengthy periods of rain were predicted.  As height was gained the sky slowly turned slate grey and the wind increased, soon the first raindrops came down and by the time we were approaching the critical bwlch the predicted rain front was bearing down on us.

Part of the area of the bwlch is now a rutted landscape consisting of stumps of felled trees and metre high furrows

We had a quick look at the area of the bwlch and decided we should press on to the summit.  The bwlch area has a forest ride going across it in a hill to hill direction that eases passage through the forest.  The dubious honour of being known as ‘The Inaccessible Pedwar’ is unwanted as where the forest ride ends a wander through mature conifers gives relatively easy access to the cairn atop the summit.

The forest ride that eases passage through the trees on the way to Moel Dimoel

I dug deep in to the fallen pine needles to try and get to ground level for measuring the height offset as the Trimble was going to be set up on the Draper tripod with its external antenna in place.

As the equipment was set up, Mark ventured down to the edge of the trees to look over the cliff to a very soggy looking valley.  The weather had indeed closed in with rain sweeping across the landscape, but in the forest we were completely sheltered and enjoyed the relative dryness during which the Trimble locked on to a number of satellites and gathered 16 minutes of data.

Gathering data at the summit of Moel Dimoel as darkness quickly approaches

From here we visited the bwlch and got rather wet.  Part of this area now resembles a buldozed landscape as metre high trenches exist with a deep water channel also in place.  We decided the terra-forming was too great to consider any of this land to be ‘natural’ and placed the Trimble on the low point of the forest ride on the hill to hill traverse.

Getting wet at the bwlch 

After data collection we set off from the area of the bwlch with just enough light to make our way down the forest track and arrived at the car at 4.35pm.

Survey Result:

Cyrniau

Summit Height:  488.2m (converted to OSGM15)

Summit Grid Reference:  SJ 06309 25183

Bwlch Height:  382.2m (converted to OSGM15)

Bwlch Grid Reference:  SJ 05374 24742

Drop:  105.9m (Hump status confirmed)

Dominance:  21.70%

Moel Dimoel

Summit Height:  494.5m (converted to OSGM15)

Summit Grid Reference:  SJ 02839 25512

Bwlch Height:  460.2m (LIDAR)

Bwlch Grid Reference:  SJ 02536 25480 (LIDAR)

Drop:  34.3m (Trimble summit and LIDAR bwlch)

Dominance:  6.94% (Trimble summit and LIDAR bwlch)

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