Sunday 27 August 2017

Mapping Mountains – Trimble Surveys – Foel Cedig



17.06.17  Cefn Brân (SJ 096 199), Pen y Bylchau (SJ 062 203) and Y Glog (SJ 088 207)

Y Glog (SJ 088 207)

Having had the pleasure of an evening’s company with Alan Dawson I headed out the following morning in beautiful blue skied conditions, whilst Alan set off to meet his sister for a walk up Cadair Idris.  My destination was not as ambitious and consisted of a couple of hills above Llanfyllin.

Parking my car I sauntered down the narrow lane aiming for a public footpath that led across fields toward a high lane where the first summit of the day was closely positioned.  There was intensity to the heat, thankfully this was dry and not a humid overbearing and oppressive heat, with colours bouncing across the land as a deep blue sky radiated from above.

Cefn Brân (SJ 096 199) from the lane leading to Hafod

The path led past the farm of Hafod and continued up slumbering fields where sheep were haphazardly placed nonchalantly grazing, as the path continued below a conifer plantation positioned to the south of the high lane and towering up the hillside, the summer growth almost became overwhelming with fern sprouting waist high and stunted trees overhanging the lower hillside.  Picking a way through I found what I thought to be the continuation of the path and followed it up to open fields and the high lane beyond, with the summit of my first hill; Cefn Brân now being only a short distance away.

I stopped before the summit to talk to a farmer who was mending the fence on the south-western side of the high lane.  We chatted for quite some time, pointing out the far hills and commenting on how beautiful this part of the country is.  He had no objection to me visiting the summit, and so I headed off to find its high point and set the Trimble up to gather its allotted five minutes of data.

Gathering data at the summit of Cefn Brân

Once data were stored and the Trimble packed away I walked back to the farmer for another chat and then proceeded down the lane to where the critical bwlch of Cefn Brân is situated.  I’d taken a Google car over this spot the previous evening and judged that the critical point of the bwlch was placed on the lane close to where the 361m spot height appears on the Ordnance Survey enlarged mapping hosted on the Geograph website.  Arriving at the low point of the lane I peered through the hedge on its northern side and walked up the western part of the lane to look back down on the area of the bwlch, I picked my spot and positioned the Trimble and then repeated what I had just done, by doing so I noted the marshy land on the north of the lane and where it bisected the paved narrow road, I re-positioned the Trimble by a few metres and then repeated the whole process again, eventually I moved the Trimble from the side of the lane into the middle of the narrow road and once the 0.1m accuracy level had been obtained, I pressed Log and scampered off hoping that a rogue car would not appear in the next five minutes, thankfully none did, and once the allotted 300 datum points were stored I took a series of photographs, switched the equipment off and continued on the narrow lane heading toward the critical bwlch of Y Glog, which is placed close to a sharp corner in the road and where it bisects with a number of tracks.

Gathering data at the critical bwlch of Cefn Brân

When on top of Cefn Brân I’d noticed that forestry had been felled on a summit beyond Y Glog, and studying the map it looked as if it was the summit of Pen y Bylchau, which is listed as a Pedwar.  The easiest route to the summit of this hill was from the sharp bend in the narrow lane that I was now heading toward and then up one of the tracks that bisect it.  Although concerned that the extra couple of miles from this bwlch to the top and back may prove problematic for my wonky knee I decided the opportunity to Trimble a summit that has been immersed in conifer plantation for years was one not to miss.

Once at the sharp bend in the narrow road I spent a number of minutes assessing the lay of land before choosing the spot for Trimble placement, this proved to be near an overhanging tree and it took an inordinate amount of time for the o.1m accuracy level to be attained before data should be logged, I spent this time sitting on a felled bough of a tree, in the shade as the sun roasted down.

Gathering data at the critical bwlch of Y Glog

As the Trimble beeped away collecting its 300 allotted datum points my mind wandered to all manner of places, once five minutes were up I switched the Trimble off, packed it away and headed up one of the tracks, this soon petered out to a vehicle track that headed toward a gate.  I then followed a fence line across rougher grass land toward a slow and sweat induced last uphill toward the summit, crossing the fence I stumbled through the customary chaos of felled conifer plantation to what I judged to be the high point, this I again assessed from a number of directions and once happy with the Trimble placement I sat on a near tree stump, basking in the sun as five minutes of data were gathered.

Cefn Brân from the lower slopes of Pen y Bylchau

The approach to Pen y Bylchau

Gathering data at the summit of Pen y Bylchau (SJ 062 203)

Across the intervening valley the sun drenched top of Rhialgwm looked impressive above its conifered lower south-eastern slopes, whilst far off to the west the shapely profile of Cadair Idris stood out with Alan and his sister somewhere near its summit.

The shapely profile of Cadair Idris which Alan Dawson was surveying at just about the same time

After stumbling my way back through the debris of felled forestry I followed a different vehicle track down the hill, only cutting across the slopes lower down to re-join my inward route back to the sharp bend in the lane, and then onward back up the lane to where it intersects with another narrow road that would eventually lead me back to my car.

Delicate clouds out to the north on the way toward Y Glog

I left the lane where a gate gave access toward the southern slopes of Y Glog and followed a fence line toward its summit, once at the top I checked the ten figure grid reference I’d noted from the Hill Bagging website and found that the point where I judged to be highest was the farthest west of three rises, with the one farthest east obviously lower.  Before activating the Trimble I checked the central top against the more westerly and still thought the westerly summit to be higher, as the Trimble gathered data on the westerly high point I decided I should also gather data from the central top, and to complete proceedings I thought I’d better also gather data from the lower easterly top, by doing so there would be a good comparison between the Trimble data and map spot heights, and I’ve also learnt that if presented with an opportunity to put an accurate height on a hill then do it, as the opportunity to do so may never present itself again.

Gathering data at the summit of Y Glog

During these three data sets I stood in the sun keeping my eye on any rogue wandering sheep nearing the Trimble, I also rested, luxuriating myself in warmth and happy in the knowledge that another three summits had been Trimbled.

The descent route although simple and relatively short was a joy, as the whole area was quiet and devoid of activity, I followed the easterly grassed ridge of Y Glog down to a gate which gave access back on to the narrow country lane and then wandered down to my car.  It had been a hot but very enjoyable few hours on the hill, all that remained was a drive to Oswestry to visit Lou for the evening.



Survey Result:



Cefn Brân  

Summit Height:  391.3m (converted to OSGM15) 
 
Summit Grid Reference:  SJ 09634 19959

Bwlch Height:  361.3m (converted to OSGM15)

Bwlch Grid Reference:  SJ 09289 20126


Dominance:  7.68%





Pen y Bylchau

Summit Height:  456.7m (converted to OSGM15) 
 
Summit Grid Reference:  SJ 06218 20307

Bwlch Height:  c 371m (interpolation)

Bwlch Grid Reference:  SJ 07137 21187 (interpolation)

Drop:  c 86m

Dominance:  18.76%





Y Glog

Summit Height:  408.2m (converted to OSGM15) 
 
Summit Grid Reference:  SJ 08867 20735

Bwlch Height:  346.3m (converted to OSGM15)

Bwlch Grid Reference:  SJ 07784 20140

Drop:  61.9m

Dominance:  15.16%








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