Saturday 10 November 2018

Mapping Mountains – Trimble Surveys – Hirddywel



04.08.18  Garn Fach (SO 041 815), Waun Ddubarthog (SO 033 816), Pegwn Mawr (SO 023 812), Glanfeinion Hill (SO 033 846), Pt. 533.0m (SO 033 852), Pt. 516.0m (SO 047 863) and Bryn Gwyn (SO 050 877)   

Pegwn Mawr (SO 023 812)

Today proved extremely warm, and although there was a refreshing breeze for parts of the walk, the warmth sucked all energy and left a soul sapping fatigue. 

The walk had been suggested by Aled and entailed a linear route taking in Pegwn Mawr and a number of Uchaf hills to its east and north, and with many surveys planned it would no doubt confirm the classification of a number of hills and give each in turn an accurate height.

We met in Caersws and headed south-east toward the end of the paved minor lane that makes its way up toward the large mast on top of Bryn Gwyn.  Driving a Google car on this lane suggested that parking was restricted but we chanced our luck and continued driving past one potential parking place upward to a gate, as I held the gate open for Aled to drive through the sound of an approaching quad bike reverberated up the lane, it was the local farmer, within a few minutes he had driven past Aled’s car further up what was now a combination of an old paved lane and track, to a solid piece of ground on the adjacent field indicating that this would be the best place for us to park.  We stopped and chatted with him for a number of minutes and thanked him for his help.

With one car left for our descent we now drove southward toward Llaethdy where we joined another minor lane heading in to the hills, here we stopped another farmer from Ddullui Bank and asked if we could park near their farm, they kindly told us that we could drive further toward the hill on a track in to the forest, and following their instruction this is what we did, parking almost at the top of our first hill of the day; Garn Fach.

It was only a short walk from where the second car had been left to the summit of Garn Fach, firstly on a track and then forest ride to where the high point is positioned, I’d been this way many years ago but had not ventured in to the conifers that swamp this hill, and with a ten figure grid reference produced by Aled’s LIDAR analysis which gave the high point in the trees we had to succumb to all temptation to remain free of tree bashing and enter the darkness within.  Thankfully it was only a short distance to where LIDAR gives the summit of this hill to be positioned and once Trimble data were gathered we emerged back in to daylight and the increasing warmth of the day.

The Trimble set-up position at the summit of Garn Fach

Forest breaks indicated that reaching the connecting bwlch of Garn Fach would not be too difficult, on our way toward the bwlch gaps through the trees gave views toward Pegwn Mawr, aloof above all other hills in this range and now with wind turbines close to its summit, where on my first visit it had the distinct feel of a wild unencumbered hill, this has now sadly gone due to the spinning blades of these turbines, which today were static edifices of white, standing bolt upright, modern-day impositions upon an ancient land.

Pegwn Mawr

We reached a point in the forest and stopped, wondering exactly where we were, and although we checked the grid co-ordinates in the Trimble the increasing heat of the day must have been playing severe tricks as although we thought we were now at the connecting bwlch, and therefore gathered the customary data, we were in fact down stream of it!  Once data were gathered we headed out of the confines of the conifers to open hillside and made our way up summer grassland toward the summit of our second hill of the day; Waun Ddubarthog.

Again, Aled’s LIDAR analysis led us to the high point of the hill which was placed amongst reed grass close to a vehicle track through the copious amounts of grassland.  Once the allotted Trimble data were gathered we followed the vehicle track for a short distance before plunging down to the connecting bwlch.

Gathering data at the summit of Waun Ddubarthog

This next bwlch is placed in a large bog, which today was relatively dry.  As Aled investigated the small pool that feeds the emerging stream valleys I set the Trimble up and tried to find firm ground to stand on during data collection.

Gathering data at the critical bwlch of Waun Ddubarthog

It was only a short walk up toward the summit of Pegwn Mawr from this bwlch, and thankfully the roughest underfoot conditions were now behind us, but the heat was soul sapping and continued to be so for the rest of the day.

Aled heading for the summit of Pegwn Mawr

The summit of Pegwn Mawr has extensive views, which one would expect from such a prominent hill, it is crowned with a cairn which has an old elongated post stuck in it at an angle, these are positioned on an ancient turf covered barrow which dominates the position of the triangulation pillar which is set back from this high point toward the south-west.  I had not visited this summit since February 2010 when along with John Barnard and Graham Jackson we surveyed its height in relation to the flush bracket fixed to the trig pillar, it was good to be back, although the heat was taking its toll.

The summit of Pegwn Mawr

I placed the Trimble on the high point of the hill and soaked in the view and tried to recover whilst it gathered data, it was going to be a long hot day on the hill and I was already feeling debilitated.

Toward our north lay a series of hills that were in the main above 500m in height, with the next three all being listed as Uchafion, the first of which had also been surveyed for height and drop when John, Graham and I visited these hills in 2010.  However, I wanted to gather Trimble data to compare to the Leica result and the more surveys taken would equate to more rests, which even at this early stage during the walk I knew I needed.

We were now on the convenience of tracks made across these hills when the wind farm was originally installed, these at least gave easy access northward toward the connecting bwlch of our next hill, which Aled persuaded me not to survey as it had previously been surveyed with the Leica equipment.

We passed two people on horseback heading down another access track as we neared the summit of Glanfeinion Hill.  Once at the summit we assessed the lay of land, chose our spot and I set the Trimble up, a welcome sit in the heather then gave respite from the rigours of the day.

Gathering data at the summit of Glanfeinion Hill

The next bwlch connected to a 533m map heighted hill and once Trimble data were gathered we pressed on to its summit, this was placed near a large mast, and again as the Trimble gathered its allotted data I tried to recover from the heat that beat down incessantly.

Pt. 533.0m (SO 033 852)


Gathering data at the summit of Pt. 533.0m (SO 033 852)

Leaving this summit we followed an earthen track for a short distance before cutting north-eastward on a sheep track toward the next bwlch, we were now back in the summer grasslands which highlighted sunlight and shade giving a welcome contrast of colour.  Eventually we re-joined the earthen track as it headed toward the 516m map heighted summit which was our destination after the next bwlch survey.

Heading away from the track in to the grasslands


Heading toward the last two hills of the day

The bwlch was positioned in a wilderness of grass, I felt sapped of all energy whilst setting the Trimble up, and this seemed all I could now do as Aled had been using it as a hand-held device to zero in on a series of ten figure grid references I had come prepared with, and it was all I could do to create the file and press ‘Log’, I then sat in the grass and heather and waited until the allotted data were gathered and stored.

Gathering data at the critical bwlch of Pt. 516.0m (SO 047 863)

The next summit proved a delight with extensive views, stunning late afternoon colour, a trig pillar and a quiet herd of cows, we celebrated by eating spiced burger baps, a welcome addition as the Trimble gathered its data.

Gathering data at the summit of Pt. 516.0m (SO 047 863)

We were now on the last part of the walk, we had options to take in two 400m Sub-Pedwar hills but agreed that these were too much as each would require diverting from a direct route back to Aled’s awaiting car, and it was still too warm to contemplate adding undue mileage to an already exhausting day.

All that remained was a walk down the northerly ridge of the hill toward a track that headed down to the connecting bwlch of Bryn Gwyn, we stopped for a while to talk with a couple who were on their quad bike, they were local farmers and were out inspecting their sheep.  After waving them off we headed to the bwlch.

Bryn Gwyn (SO 050 877)

The critical point of the bwlch was on the track that leads across it from a west to east direction, and the customary data were taken with the Trimble.

Gathering data at the critical bwlch of Bryn Gwyn

The masts atop Bryn Gwyn looked invitingly close when descending to its connecting bwlch but proved a slow grind of uphill to reach, when at the top the high point was on the periphery of the mast compound and I proceeded to set the Trimble up positioned on a fence post having measured the offset between its internal antenna and the ground below. 

Gathering data at the summit of Bryn Gwyn

I sat in shade whilst data were collected, tired, somewhat heat battered but happy in the knowledge that another 13 data sets had been taken and that it was only a short walk down the northerly ridge fence on to the track that led back to Aled’s car.

The beauty of mid Wales

The views on the descent proved stunning with the beauty of mid-Wales laid out in front of us as dotted sheep grazed and the heat of the day turned the land to a vivid welcoming colour, it had been a good day on the hill, albeit exhausting.

That car looks like heaven on earth!


Survey Result:


Garn Fach 
  
Summit Height:  504.3m (LIDAR)

Summit Grid Reference:  SO 04184 81512 (LIDAR)

Bwlch Height:  484.3m (LIDAR)

Bwlch Grid Reference:  SO 03783 81771 (LIDAR)


Dominance:  3.97%





Waun Ddubarthog

Summit Height:  519.8m (converted to OSGM15, average of two summit surveys)

Summit Grid Reference:  SO 03324 81653

Bwlch Height:  501.2m (converted to OSGM15)

Bwlch Grid Reference:  SO 03139 81293

Drop:  18.6m (Uchaf status confirmed)

Dominance:  3.59%





Pegwn Mawr

Summit Height:  585.3m (converted to OSGM15, average of two Trimble GeoXH 6000 surveys)

Summit Grid Reference:  SO 02391 81239

Bwlch Height:  285.9m (converted to OSGM15, from previous Trimble GeoXH 6000 survey, natural bwlch)

Bwlch Height:  283.8m (converted to OSGM15, from previous Trimble GeoXH 6000 survey, disused rail cutting)

Bwlch Grid Reference:  SN 92693 80074 (from previous Trimble GeoXH 6000 survey, natural bwlch)

Bwlch Grid Reference:  SN 92601 80035 (from previous Trimble GeoXH 6000 survey, disused rail cutting)

Drop:  299.3m (natural bwlch)

Drop:  301.5m (disused rail cutting bwlch)

Dominance:  51.14% (natural bwlch)

Dominance:  51.51% (disused rail cutting bwlch)





Glanfeinion Hill (significant name change)

Summit Height:  534.8m (converted to OSGM15, Trimble GeoXH 6000)  534.9m (converted to OSGM15, Leica 530)

Summit Grid Reference:  SO 03338 84669 (Trimble GeoXH 6000)  SO 03338 84670 (Leica 530)

Bwlch Height:  506.5m (converted to OSGM15, Leica 530)

Bwlch Grid Reference:  SO 03043 83053

Drop:  28.4m (Leica 530)

Dominance:  5.30%





Pt. 533.0m 
 
Summit Height:  533.0m (converted to OSGM15)

Summit Grid Reference:  SO 03375 85269

Bwlch Height:  515.1m (converted to OSGM15)

Bwlch Grid Reference:  SO 03442 85018

Drop:  17.9m (Uchaf status confirmed)

Dominance:  3.36%





Pt. 516.0m 
 
Summit Height:  516.0m (converted to OSGM15)

Summit Grid Reference:  SO 04723 86301

Bwlch Height:  494.0m (converted to OSGM15)

Bwlch Grid Reference:  SO 04364 86248

Drop:  22.1m

Dominance:  4.28%





Bryn Gwyn 
 
Summit Height:  455.7m (converted to OSGM15)

Summit Grid Reference:  SO 05045 87789

Bwlch Height:  419.6m (converted to OSGM15)

Bwlch Grid Reference:  SO 04873 87164

Drop:  36.0m

Dominance:  7.91%










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