Saturday 11 August 2018

Mapping Mountains – Trimble Surveys – Cadair Idris


23.05.18  Ynys Gyffylog (SH 629 138)

The wooded summit of Ynys Gyffylog (SH 629 138)

Having visited some of the higher hills in the Cadair Idris range and with beautiful sun drenched weather continuing in to the early afternoon, I thought I’d re-visit the area surrounding the Arthog Bog and see if I could get to the top of another one of its landlocked islands.

I’d recently visited Fegla Fawr and Fegla Fach, both of which are the main and higher landlocked islands in this compact area, with many of these small islands wooded and rocky in nature, and the one I chose for this afternoon’s little adventure proved a rough place to visit and full of unsavoury undergrowth.

I parked adjacent to a row of terraced houses and set the Trimble on top of my car roof to log in to satellite reception, doing so would give me a ten figure grid reference to follow when on the summit area and compare to that produced by having LIDARed the hill, if indeed I made it to the summit, as what I could see of the hill looked particularly dense in foliage.

As I set off aiming for the most northerly of the terraced row of houses where I hoped a track would give me access to the hill, a man appeared walking his dog from the side of the most southerly of the houses, I smiled and said hello and asked if he was local and if so, did he know of a path leading up the wooded lump at the back of the houses, he saved the day and kindly took me to the side of his house where he directed me up steps to what he described as a path of sorts that would lead via his blue barrowed potatoes and discarded tyres and a mound of bramble and trees toward two sets of stone steps to the wilderness above.  If not for this kind gesture I doubt I would have found a way to the top.

The path starts at the front of the car on the left

The path heads up toward the blue barrel on the left and makes its way past the barrels on the right

The path crept past his potatoes and a mound of foliage above the backyards of the terraced houses toward a wooden hand rail and stone flagged steps leading steeply upward to a second set of steps that were hardly distinguishable from the undergrowth surrounding them, these led to the brackened and tree infested upper part of the hill.

Spot the path

Looking back at the blue barreled potatoes

The hand rail indicates the way upward

As I popped out on the summit ridge which could hardly be seen due to thick undergrowth the sun blazed from above, a radiant blue sky cast down warmth.  I stumbled my way through bracken trying to get to the high point which was immersed in bramble, bracken and gorse with trees obstructing any direct upward view, I thought the chances of satellite reception for the Trimble was slim.

The summit ridge

I spent a few minutes stamping down as much foliage as I could before setting the Trimble atop my rucksack, measuring the offset between its internal antenna and the ground below and then started what I thought would be a very long wait until the 0.1m accuracy level before data should be logged was attained, miraculously I only had to wait about five minutes and suddenly the magical 0.1m mark appeared on the screen and I pressed ‘Log’ and disappeared in to the foliage to wait for the allotted data to be stored.

Gathering data at the summit of Ynys Gyffylog

I let the Trimble gather 16 minutes of data and stood in the sun with hardly a view due to the trees, but I felt content and more than happy that the Trimble was performing well and had attained its accuracy level incredibly quickly considering where it was placed.  During the wait for data collection I stamped a path back to where I had popped out on the summit ridge and made sure I remembered where this place was as the last thing I wanted was an alternative route back down to safety below.

Once sixteen minutes of data were gathered I switched the equipment off, packed the Trimble away and retraced my route back down the stone steps and along the narrow path beside the discarded tyres and barrowed potatoes.

  

Survey Result:


Ynys Gyffylog

Summit Height:  23.1m (converted to OSGM15)

Summit Grid Reference:  SH 62964 13848

Bwlch Height:  2.4m (LIDAR)

Bwlch Grid Reference:  SH 63071 13758 (LIDAR)

Drop:  20.6m (Trimble summit and LIDAR bwlch) (Double Sub-Twmpau addition confirmed)

Dominance:  89.42%









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