Thursday 12 December 2019

Mapping Mountains – Trimble Surveys – Mynydd Hiraethog


18.09.19  Mwdwl Eithin (SH 917 540, only bwlch surveyed)

Having surveyed six bylchau five days ago which involved a road trip visiting friends in Llanidloes before continuing up the hill road passing Llyn Clywedog and making my way over to Talerddig and onward to Y Bala and finally the top of the B4391 as it passes over the Y Berwyn, I was in full bwlch bagging and surveying mode, and with warm blue skied weather forecast I planned another route, this time taking in nine bylchau.

Mwdwl Eithin (SH 917 540)

My planned route concentrated on the Mynydd Hiraethog hills, starting with the bwlch of their highest hill; Mwdwl Eithin, which is positioned in a bog beside the A5 road between Cerrigydrudion and Glasfryn.  My route would then continue up the A453 road heading north-eastward picking off a series of Pedwar and Trichant bylchau on or beside ever narrowing roads before heading down to the valley to survey the bwlch of Moel Fama and ending atop Bwlch Oernant (Horseshoe Pass) and revisiting the bwlch of Cyrn y Brain.

Prior to setting off I’d spent a few hours scrutinising map contours, visiting each area in a digitised Google car assessing the lay of land and prospective parking places, and noted any LIDAR grid references produced by Aled Williams.  Prepared for my day in field and bog I set off over the Y Berwyn and onward toward the A5 arriving at my chosen parking place at approximately 9.00am.

The parking place was a grassed entrance giving access to a gate and was the second one I had pulled up in, with the first a mile or so before the bwlch.  Having parked up at the first I checked the grid co-ordinates in the Trimble and realised my error and drove the short distance further west to where my car could be safely parked beside the road.

Leaving the car I walked over the road and found a drainage ditch following the course of a barb wired fence on its opposing side, this wasn’t ideal.  I had to find a suitable crossing.  Thankfully the pavement eased safe passage beside the road before I had another look over the intervening fence; eventually what looked like a semi-solid grassed section broke the course of the drainage ditch.

The A5 with the bwlch of Mwdwl Eithin on the right beyond the trees

Once over the fence I switched the Trimble on and used an interpolated grid reference produced from the 5m contouring on the OS Maps website to zero me in to where the bwlch of Mwdwl Eithin is situated. 

The morning still had a slight chilled air, which soon disappeared as the sun’s strength heralded a beautiful day ahead.  Dew laden grasses greeted me as I walked across the rough ground zeroing in on the grid co-ordinates of the bwlch.  A myriad of delicate webs highlighted against the dewed morning and low sun were intricately balanced amongst the grassed surrounds.  It was a pleasure to be in such a place, a seeming other world of finite detail etched in memory and all next to a busy main road where the hummed thud of traffic sped ever onward.

Dew laden webs

The ground where I placed the Trimble atop my rucksack was rough and consisted of tussocks.  The placement was indebted to interpolation of contours.  As the equipment beeped away gathering its all-important data I stood in the morning sunshine luxuriating in warmth and let my mind wander.

Gathering data at the bwlch of Mwdwl Eithin

After the allotted data were gathered and stored I closed the equipment down, packed it away and walked the short distance back toward an intervening low hung barb wired fence giving access to the only semi-solid patch of grass that I found and which broke the course of the drainage ditch.  I had investigated a part of the latter when data were being gathered and decided against any attempted crossing, and proceeded to clamber back over the fence next to the road.  From here it was only a short walk on the pavement to my awaiting car, and with what I envisaged to be one of the most difficult of the day’s surveys complete I headed further west toward the A543 junction and the second bwlch survey of the day, which connects with the marginal Pedwar of Pen yr Orsedd.



Survey Result:


Mwdwl Eithin

Summit Height:  532m (triangulation pillar)

Summit Grid Reference:  SH 91709 54055 (triangulation pillar)

Bwlch Height:  268.8m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 92867 49956 (Trimble GeoXH 6000)

Drop:  263m (triangulation pillar summit and Trimble GeoXH 6000 bwlch)

Dominance:  49.47% (triangulation pillar summit and Trimble GeoXH 6000 bwlch)


  





No comments: