Monday, 8 January 2018

Mapping Mountains – Trimble Surveys – Pumlumon

29.10.17  Coed Pant y Glo (SH 767 014)

Coed Pant y Glo (SH 767 014)

Coed Pant y Glo nestles in to its landscape; almost forgotten it overlooks the flat bedded land of the Dyffryn Dyfi to its north and the A 489 road leading toward Machynlleth to its south.  Its summit is just within the wood where the hill takes its name from, with a number of near and attractive tops outside of this wood and all of which are lower.

I approached from the south-east following a public footpath beyond the grounds of Gallt-y-llan; a substantial house at the end of the paved road.  As I clambered up beside a garage and over a rusted low gate the afternoon’s sunshine added warmth to proceedings.

The gate gave access to a steep brackened field where two further gates led toward the summit area of the hill.  Across the valley the summits of Copa Shon and Pen y Graig Fawr dominated, I’d just visited each and it felt good to look out toward them from a different perspective.

Before heading in to the deciduous wood I assessed the high point of land outside of the wood, deciding that the survey of this point could wait I ventured across to the boundary fence, stretched over it and stood on the high point of the hill.  The summit of this hill is easily found and consists of land a metre from the boundary fence, beyond which the ground drops steeply to the south.

I set the Trimble up on top of my rucksack to give it elevation above its immediate surrounds and measured the offset between its internal antenna and the summit of the hill at the base of the rucksack, once the file was created in the Trimble I stood back and hoped I would not have to wait long before the 0.1m accuracy level was attained before data should be logged.

Gathering data at the summit of Coed Pant y Glo

During this waiting process I savoured the wood and its trees and its moss and its peacefulness; nothing seemed to stir except for the occasional flutter of a bird.  Eventually I activated the Trimble and again stood back amongst the trees and waited until the allocated datum points were collected and stored, once this was done I closed the equipment down, took a few photos and headed back to the high point of ground outside of the wood.

Moss on tree

This outside of the wood high point was on a grassed mound, similar in nature to a number that sprang up on the summit area, I placed the Trimble on the ground and waited for 300 datum points to be collected and stored before closing the equipment down.

Gathering data at the high point of land outside of the wood, with the wooded summit in the background of this photo

Leaving the summit area of Coed Pant y Glo it was only a short walk back on my inward route toward my car, I then headed toward Gallt y Gog; a lower forested P30 directly above Machynlleth.  Afterward I surveyed the bwlch of each hill.

The bwlch of Coed Pant y Glo is positioned in a field beside a drainage ditch which has a land bridge spanning the ditch leading down from an access gate.  I parked a short distance away down the road at the entrance to a caravan park and soon found myself standing beside a stunted tree hedge next to a bungalow, having set the Trimble up at what I deemed to be the high point on the valley to valley traverse and which was beside the drainage ditch.

Gathering data at the first Trimble set-up position at the bwlch of Coed Pant y Glo

I spent the next five minutes standing beside the hedge waiting for the Trimble to gather its allotted data.  On the other side of the hedge were a greenhouse and the back garden of the bungalow. 

Before heading back to my car I took another data set from the land bridge that spans the small wet ditch, this I decided would be the critical bwlch of the hill.  As I did so I watched the lowering sun cast colour across the opposing land, I was now in shade which only enhanced the illuminated colour on show.

Gathering data at the second Trimble set-up position at the bwlch of Coed Pant y Glo

I’d taken eleven data sets during the day on three separate walks and had visited five P30s and been out surveying for eight hours, it had been another good day. 
Survey Result:

Coed Pant y Glo (significant name change)

Summit Height:  140.7m (converted to OSGM15)  

Summit Grid Reference:  SH 76776 01435

Bwlch Height:  49.3m (converted to OSGM15)

Bwlch Grid Reference:  SH 77919 01206

Drop:  91.5m (Subhump status confirmed)

Dominance:  65.00%

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