Tuesday, 21 October 2014

Mapping Mountains – Trimble Surveys – Y Berwyn

19.10.14  Pen y Berth (SJ 081 127)  

The conifered summit of Pen y Berth (SJ 080 127) off in the distance
Sometimes the seasonal change amongst the hills can be dramatic.  This year the late summer warmth of September was swept away with October’s first winds and then along came the succulent colour.  Today that seasonal change manifested itself in hillsides aglow with yellowed bracken and dark grey rain clouds sweeping eastward pushed along by a strengthening westerly.

The hills for today’s two little wanders had been suggested by Mark who was busy tidying up his Section 30E and 31A Humps.  The first hill Mark wanted to visit was Pen y Berth which is situated just east of Dolanog and rises above the B4382 to the south and the Afon Efyrnwy to the north.

We parked in a lay-by at SJ 072 127 which is large enough to accommodate five or six cars.  The footpath heading north-eastward from the lay-by is on Glyndŵr’s Way and forms part of the 217km (135 mile) long distance walk that starts / finishes in Welshpool and Knighton.

The initial part of our walk was just above the Afon Efyrnwy as it heads eastward to its meeting with the Afon Hafren at the border with England.  At this point the Efyrnwy forms a number of pools well known locally for summer swimming, today its waters bubbled down past fields and hillsides scattered with fallen autumnal leaves.

On part of Glyndŵr's Way as it contours above the Afon Efyrnwy
As we made progress above the river the first of the predicted showers fell upon us, the forecast was for heavy downpours quickly being blown eastward.  Thankfully the rain was only intermittent and as we headed up on open hillside out of the lower growth of trees the rain ceased and was replaced with unseasonably warm sunshine.

Pen y Berth was first listed as part of the Welsh 200m P30 hills that were published on Geoff Crowder’s v-g.me website.  An accompanying note for the hill states ‘Two points of same height’.  This comment was based on the hill having two tops both of which had no spot height on the maps of the time but both with uppermost c 280m ring contours.  Nowadays the Ordnance Survey enlarged Geograph map give each top a 282m spot height.

Autumnal colour as the showers to the west begin to mass
Once on open hillside we followed green ways past yellowed bracken up to a wall which led to a small path heading up to the bwlch between the two tops.  We visited the more easterly one first which is positioned in a copse of deciduous trees and has an attractive uppermost ridge with embedded small rocks breaking out of the ground on its spine.  The Trimble was placed on the point judged to be the highest and gathered five minutes of data.

Approaching the easterly top of Pen y Berth

Gathering data on the easterly top
To our west the shower clouds were massing and as we headed toward the more westerly top the land to our south grew a darkened grey as it was duly swamped with the wet stuff.  The showers looked heavy but as of yet we had survived almost intact and relatively dry.

The westerly top is immersed in conifer plantation with its easterly point having mixed larch, it was this point we concentrated on for a survey.  I’d brought a one metre high pole to fix the Trimble on so it could be elevated above the ground.  This was pushed into the ground at the high point and we waited in the knowledge that the accuracy of 0.1m may not be attained because of the tree coverage.  After waiting ten minutes I inspected the screen and abandoned this point as the figure read 2.3m of accuracy.

The unsuccessful attempt to gather data at the easterly point of the westerly summit
I then positioned the pole in a slight clearing and levelled the top of the pole to the high point we had reached.  This would give a height equivalent to this high point.  Once the accuracy was attained I pressed ‘Log’ and hid in the trees for the five minutes of data collection. 

Aligned to the high point in the conifers the Trimble gathers its data
As the equipment was packed away the next shower skimmed us and the wind blew, it looked as if we would get soaked on our descent but again we were lucky as the heavy shower hit the southern lands and we arrived back at the car and headed off toward Y Byrwydd the next Hump of the day.

Survey Result:

Pen y Berth

Summit Height:  287.5m (converted to OSGM15) (significant height revision) 

Summit Grid Reference:  SJ 08126 12730 (summit relocation confirmed)

Drop:  134.2m (converted to OSGM15)

Dominance:  46.68% (Lesser Dominant status confirmed)


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