Saturday, 23 April 2016

Mapping Mountains – Trimble Surveys – Arenig


10.04.16  Bryn Mawr (SH 830 259) and Foel Ddu (SH 818 245)  

Bryn Mawr (SH 830 259)

For many years I’d wondered if I had reached the highest point of Bryn Mawr, as on my previous visit I’d stood on what my memory told me was the highest point of the hill and looked east toward another high point that was immersed in a conifer plantation.  Having no hand-held GPS I could now only go on what my memory told me and compare this to current maps, and these show the high point of Bryn Mawr with three 400m ring contours, with two of these including the furthest easterly 401m spot heighted summit within the boundary of the conifer plantation.  Had I reached the true summit or was I standing on a near 390m ring contour looking toward the high point and never actually going to it.  Armed with my Trimble it was time for me to repeat my visit and be sure that I had finally reached the summit. 

I left my car at Pont Fronwydd and followed a footpath on the north-east side of the Afon Mynach as it tumbles down from wilder higher climes to the valley below.  The morning’s chill gave a prospect of clear conditions but I knew that it would be breezy as the forecast predicted 17mph winds in lower parts.

The footpath hugged the southern part of Carreg yr Aderyn which is now swamped in conifer plantation, these swayed in the morning’s sunshine as buffets of wind blew through their branches.  The footpath joins a track higher up close to Cae Llwyd, a single house looking out on a beautiful scene of ruggedness.  Leaving the path I gained height keeping the forestry on my right.  Across the Afon Mynach the blackened profile of Foel Ddu loomed skyward, looking rather uninviting as my recollection was that pathless heather predominated on this hill.

Foel Ddu rising above the lonely house of Cae Llwyd

As I followed the forestry I checked the co-ordinates in the Trimble for the ten figure summit grid reference, after following a wet sheep path adjacent to the trees I reached their high point and peered in to them for the summit of a hill, non-existed, but behind me to the south-west a number of bumps were significantly higher than any ground in the forestry, it seemed I had reached the high point on my previous visit and that the placement of the conifer plantation is incorrect of current maps.

I surveyed the high point of each 400m ring contour in turn and positioned my rucksack on the ground, resting on its back instead of the customary base which only elevates it above the ground by an approximate 0.28m.  This would elevate the Trimble above the moorland surroundings of grass but would keep it relatively close to the ground as the wind consistently breezed through the land and positioning it any higher was running the risk of wind wobble.

Gathering data at the central 400m ring contour on Bryn Mawr

During these three surveys I stood a safe distance away from the equipment with my back braced against the chill wind and looked out on a sun bleached land of mountain top, heather, rock and beauty – a stunning place.

Craig y Benglog (SH 805 244)

The blackened profile of Foel Ddu

Happy that I had re-claimed the summit of Bryn Mawr I contemplated heading back to my car, but I also wanted to survey the critical bwlch of the hill.  This took me on to land that must surely be seldom visited except for an occasional passing farmer on a mud splattered quad bike, as few hill walkers would have the necessity to visit.

The bwlch is positioned in a wild bog of knee high tussock grass forlorn and empty, a quiet haven amongst a bed of nothingness.  For me this is one of the beauties of surveying as if not for this unusual activity and inner need to catalogue I would not visit such places, and many have a beauty all to themselves.

Gathering data at the critical bwlch of Bryn Mawr

The desolation of bwlch surveying

I could now either head back to my car, bi-passing the heathery delights of what looked like a watery bwlch adjoined to Foel Ddu and its pathless heather bound summit, or I could plod on in to the morass of wilderness.  I almost talked myself in to the former, but I just couldn’t resist the temptation and except for the wind the day was rather stunning as colour poured down on the land with succulent clear blues etched against the bleached and lonely moor whilst mountain peaks cast down upon the scene.

The connecting land between each hill proved a slow stumble as I followed a collapsed and old wall up toward the bwlch that connects Foel Ddu with Carreg Lusog.  As I arrived at its high point I looked down on to a wide, tussock and bog ridden bwlch that immerses itself in heather, this looked like fun.

I stumbled my way in to the bwlch and splashed from one bog infested tussock to another, each time I assessed the lay of land another point looked as if it was the point where the valley to valley traverse meets the hill to hill traverse.  I eventually set the Trimble up at two points, one where map interpolation suggests the bwlch to be positioned and another where I thought the critical bwlch lay.  Each survey was a wild affair as I tried to keep me, my rucksack and the Trimble out of the oozing water under each tussock.  As the Trimble did its stuff I waited and watched the light on Carreg Lusog and Craig y Benglog, each bringing back memories of past surveys.

Carreg Lusog (SH 818 264)

Gathering data during one of the surveys for the position and height of the critical bwlch of Foel Ddu

After the bog laden bwlch survey I squelched my way up on to relatively dry ground and followed a fence toward the summit of Foel Ddu.  I’d noted a ten figure grid reference for the summit from the Hill Bagging website but found that my eye judged the higher point to be a little further south, and when I arrived there I dug out a heather bound summit cairn.  I gathered data from this point and the high ground near to the grid reference I’d noted.  During this the wind whipped across the upper part of the hill.  To my north the forever blackened profile of Y Dduallt rose above the gentler but still rugged slopes of Carreg Lusog.

Y Dduallt and Carreg Lusog from the ascent of Foel Ddu

Gathering data at the summit of Foel Ddu

All that remained was to slowly stumble down the hill’s pathless northern ridge to where I’d previously followed the collapsed old wall, from here a path descended toward the track near to Cae Llwyd.

Leaving the wind-blown summits, the warmth of spring was evident as I made my way down the track, with white born lambs sitting nestled in the sunshine, eyes closed and dozing until I slowly crept up to take their photograph.





Enjoying the sunshine

Survey Result:


Bryn Mawr

Summit Height:  401.6m (converted to OSGM15) (Pedwar status confirmed)

Summit Grid Reference:  SH 83087 25918

Bwlch Height:  360.6m (converted to OSGM15)

Bwlch Grid Reference:  SH 82629 26107

Drop:  41.0m

Dominance:  10.21%



Foel Ddu

Summit Height:  465.0m (converted to OSGM15)

Summit Grid Reference:  SH 81870 24547

Bwlch Height:  377.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 81730 25060

Drop:  87.1m

Dominance:  18.73%



For further details please consult the Trimble survey spreadsheet click {here}






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