Monday, 31 May 2021

Mapping Mountains – Trimble Surveys – Arenig

 

02.04.21  Pt. 522.7m (SH 744 433), Pt. 516.0m (SH 742 433), Y Garnedd (SH 741 431) and Carreg y Foel Gron (SH 744 427) 

Carreg y Foel Gron (SH 744 427)

Between the lockdowns imposed last year, Aled and I surveyed a number of hills around and including Graig Goch (SH 751 447).  This hill is impressive with its westerly facing crags always a delight to view.  The day proved wonderful with clear blue skies, albeit chilled for much of the day. 

To the south of Graig Goch lies Y Garnedd, these two hills can be easily combined but surveying necessitates an inordinate amount of time spent concentrating on one patch of land, therefore when visiting Graig Goch it was this hill that we concentrated our efforts on and the survey of Y Garnedd would have to wait for another day.  That materialised today and conditions were remarkably similar to our outing on Graig Goch; with clear blue skies but with a chilled easterly breeze. 

I met Aled in the parking area beside Llyn Dubach and we soon had the second car parked at the end of the fisherman’s track, which enabled us to also survey the connecting bwlch between Y Garnedd and Graig Goch. 

The route to this bwlch is simple but can be rather boggy.  We found the critical point of the bwlch positioned beside a stone wall below an imposing lump of rock.  As the Trimble gathered its allotted data we caught up with all manner of things, mainly hill related, but as ever it was good to chat.  Email contact or zoom meetings for those inclined, was a means to keep in contact during the various Covid lockdowns, but nothing betters face to face contact. 

Heading toward the bwlch of Y Garnedd

Between this bwlch and the summit of Y Garnedd are two lower prominence hills that we wanted to survey.  I’d surveyed each with my basic levelling staff in September 2004, now we had the opportunity to produce far better data and determine an accurate drop value for each. 

Pt. 522.7m (SH 744 433)

The first of these hills is given a 522m summit spot height on the Magic Maps website and its high point was easy to identify and consists of rock.  As the Trimble quietly beeped away I scribbled all necessary details in my notebook and after the allotted data were gathered and stored, I closed the equipment down and joined Aled as we sauntered the short distance down to its connecting bwlch. 

Gathering data at the summit of Pt. 522.7m

Gathering data at the bwlch of Pt. 522.7m

Prior to our visit Aled had assessed the details for these hills using 5m contouring and produced interpolated ten figure grid references for each bwlch position, these proved a good indicator for where these critical points lay and once there we then assessed the lay of land by eye.  The critical bwlch for this first hill was positioned amongst moor grass close to an unsavoury pool of stagnant water, which I plunged a boot in to when trying to step across it. 

Pt. 516.0m (SH 742 433) 

It was only a short distance to the second of these two lower prominence hills and we found its connecting bwlch to be positioned on an attractive flat rocky rib, and within a few minutes the Trimble was set up gathering data. 

Gathering data at the bwlch of Pt. 516.0m

Gathering data at the summit of Pt. 516.0m

The summit of this second hill has a wonderful viewpoint with the crags of Graig Goch and the dappled blue waters of Llynnau Gamallt on grand display, whilst the bulk of Y Garnedd rose to our south with its westerly facing cliff looking impressive. 

Y Garnedd

Whilst summit data were gathered I sat with Aled and enjoyed a couple of sandwiches, it was good to be here.  The hills are wonderful places, they can be investigated on solo expeditions or in company, they give individual as well as shared experience and today these hills were an ideal place to catch up after many months of lockdown and enjoy their surroundings. 

Heading up Y Garnedd

Once the Trimble was packed away I followed Aled up the steep grassed and broken ground beside the edge of the westerly cliff of Y Garnedd, stopping occasionally to look back toward Graig Goch.  What a place to be, with the higher Eryri peaks dominating the extended view and unadulterated blue sky stretching in all directions. 

Graig Goch and Llynnau Gamallt

Graig Goch

The high point of Y Garnedd is beside the lower of two cairns and once the Trimble was set up gathering data I joined Aled in the near wind shelter and waited for data to be stored.  During this we heard the rumbling of a vehicle; it sounded similar to a quad bike but once the allotted data were gathered and stored and the Trimble closed down, a 4x4 vehicle suddenly emerged making its way toward us.  This was a surprise to say the least; I’d rarely seen such a vehicle so high on a Welsh hill before. 

Gathering data at the summit of Y Garnedd

I scampered the few metres to say hi to the driver and he pulled up straight next to the summit.  We spent about ten minutes chatting with Tom Ashman and his friend, they’d come from Penmachno and Tom said that he’d driven to this summit a few times before.  I took a number of photos as the vehicle looked so unusual parked beside the summit. 

An unexpected visitor

We left Tom and his friend at the top of the hill and followed the vehicle track down toward the access track that makes its way to the disused Foel Gron Quarry; this gave us our onward route to the last summit and survey of the walk. 

Carreg y Foel Gron is an unusual hill as its connecting bwlch with Y Garnedd is relatively flat.  The flat part of this bwlch is due to waste spoil from the old quarry and therefore is not natural.  The natural bwlch is now buried under who knows how many metres of waste spoil.  Dotted across the bwlch are large boulders, a single one being prominent whilst others are grouped together. 

Approaching Carreg y Foel Gron

As the summit of this hill is given a small uppermost 500m ring contour and bwlch contouring between 470m – 480m on contemporary Ordnance Surveys maps it was a candidate for Dewey status many years ago.  Therefore, armed with my old basic levelling staff I surveyed this hill for drop, resulting in a value of 86ft / 26.2m.  This was in June 2000; and in April 2008 John Barnard and Graham Jackson line surveyed this hill, resulting in 26.52m of drop.  These measurements were taken from the flat bedded connecting bwlch and not natural ground at its base; however John and Graham also took measurements from this area and proved that the drop value for the hill cannot exceed 29.4m.  Today we wanted to give the hill an accurate summit height. 

Aled arrived at the summit first and directed me to where the Trimble should be positioned.  It was soon set up gathering its all-important data; during this we sat, rested, chatted and enjoyed the view.  Once the Trimble was packed away we retraced our inward route back to the bwlch and continued down the old quarry track to the paved road and my awaiting car parked beside Llyn Dubach. 

The Trimble set-up position at the summit of Carreg y Foel Gron

I then drove the short distance up the road and then the rutted fisherman’s track to collect Aled’s car.  Leaving Aled to get his walking boots off, I waved my goodbye’s and headed east for another small walk taking in Garth Goch (SH 952 357) and Garth Rhiwaedog (SH 950 349) which are positioned to the east of Y Bala.

 

Survey Result: 

 

Pt. 522.7m

Summit Height:  522.7m (converted to OSGM15)

Summit Grid Reference:  SH 74459 43396 

Bwlch Height:  508.8m (converted to OSGM15)

Bwlch Grid Reference:  SH 74498 43304

Drop:  13.9m

Dominance: 2.66%


 

 

Pt. 516.0m

Summit Height:  516.0m (converted to OSGM15)

Summit Grid Reference:  SH 74296 43367 

Bwlch Height:  504.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 74371 43318

Drop:  11.6m

Dominance: 2.24%


 

 

Y Garnedd

Summit Height:  552.9m (converted to OSGM15)

Summit Grid Reference:  SH 74199 43111 

Bwlch Height:  475.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 74780 43642

Drop:  77.6m

Dominance:  14.04%


 

 

Carreg y Foel Gron

Summit Height:  500.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 74464 42764 (Trimble GeoXH 6000) 

Bwlch Height:  471.3m (relative to Trimble GeoXH 6000 summit and line survey drop)

Bwlch Grid Reference:  SH 74591 42833 (hand-held GPS via survey)

Drop:  29.4m (line survey with natural bwlch under landfill)

Dominance: 5.87% (Trimble GeoXH 6000 summit and line survey drop) 

 

 

 

For further details please consult the Trimble Survey Spreadsheet

 

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