Sunday, 20 March 2016

Mapping Mountains – Trimble Surveys – Arenig


14.03.16  Bryn Glas (SH 735 420), Pt. 483.6m (SH 735 428), Pt. 474.4m (SH 732 429) and Craig y Garreg Lwyd (SH 730 427)  

Pt. 483.6m (SH 735 428)

Occasionally the serenity of landscape and in particular the hills therein, give wonderment when colour and form merge in a harmonious beauty that can leave a numbness of feeling.  For me, this occasionally happens when the hills are quiet places, seemingly untrodden except for my own presence.  Today was such a day, a quiet sun drenched day amongst a compact group of hills whose summits I’d only visited once before.  They have a special presence as a similar feeling also enriched me on my only other visit.  These hills are positioned to the east of Llan Ffestiniog and rise above the waters of Llyn Morwynion.

I’d wanted to re-visit these hills for a number of years and with a forecast predicting the easterly March murk to break giving early spring sunshine by late morning, I took my opportunity and headed west.  The cloud murk broke as I travelled over the Berwyn and all land to the west shone under blue sky. 

As I walked the few metres down the road to the gate giving access to the southern shore of Llyn Morwynion, a brisk easterly breeze blew in, refreshing the land and anyone who walked through it, and this remained with me for the rest of the day and chilled proceedings when the sunshine would normally have warmed.

My objectives for the day took in a number of surveys, with the Sub-Pedwar of Bryn Glas and numerous bumps at the summit of the highest hill of the day positioned above Llyn y Drum being the priority.

As I surveyed the first of many points for the critical bwlch of Bryn Glas the waters of Llyn Morwynion dazzled a radiant blue.  Leaving the Trimble atop my rucksack quietly beeping away as its allotted 300 data points were gathered, I walked toward the lake and looked out on a pair of Canada geese wagh-onking their distinctive voice into the easterly breeze as it rippled against the blue watered tide.

Gathering data at the critical bwlch of Bryn Glas


Canada geese on Llyn Morwynion

I knew that there may be many surveys to conduct during the day as there are four small contour rings at the summit which nestles above Llyn y Drum and a few other bumps that also needed Trimbling, but I didn’t realise that I would also survey four separate points for the critical bwlch position of Bryn Glas.  When on my own and if the weather and daylight hours are favourable this does not concern me, the pleasure of being out on the hill and standing, waiting, and looking, and thinking, is enough for me, pressure ebbs away and a single minded resolve to enjoy and to gather data sets is fulfilment enough.

Bryn Glas (SH 735 420)

After surveying the summit of Bryn Gas I walked down to the shore of the lake and gathered data sets on two dams, the first larger and more robust than the second.  Each time I waited and almost trance like looked out across the waters to the cliff topped summits of Y Garnedd and Carreg y Foel Gron, each looked down on the scene with sublime shape of formation.

Gathering data at the summit of Bryn Glas


Y Garnedd


Carreg y Foel Gron

Once happy that all options for the bwlch position of Bryn Gas had been surveyed, I continued walking close to the western shore of the lake, before heading up to the connecting bwlch between the hill that is currently listed under the Point (Pt.) notation that nestles its presence above the rounded shape of Llyn y Drum and the higher and more dramatic summit of Y Garnedd.

The vantage point of the bwlch opened up the view to the north-west, this land was bathed in bleached early spring sunshine, whilst away to the east the distinctive high Arennig shone grey and white with pockets of snow clinging on against the onset of spring’s warmth.

Gathering data at the critical bwlch of Pt. 483.6m

To my immediate west was the summit area of a Pedwar whose summit position was previously listed due to a 486m spot height on Harvey maps.  This summit position had officially moved from this point to another near bump after a visual inspection by Aled.  I planned to get Trimble data at each point and the two other 480m ring contours in the vicinity and anything else that looked as if it needed a good Trimbling, little did I know that this would consist of nine data sets, and this was boosted to eleven with the inclusion of a bwlch and summit of a potential new 400m Sub-Pedwar.

Gathering data at the first of nine surveys for the summit position of Pt. 483.6m.  The Trimble is positioned on the old summit where the 486m spot height appears on Harvey maps and which was Trimbled as being 482.7m (converted to OSGM15) high.  The highest point of the hill and the new summit is almost directly above the Trimble and just to the left
This point proved to be the second highest on Pt. 483.6m and was Trimbled as being 483.507m (converted to OSGM15)
Gathering data at the new summit of Pt. 483.6m and which was Trimbled as being 483.574m (converted to OSGM15)

During the process of surveying all of these points I stood with my back to the easterly wind and tried not to get too chilled, only resorting once to putting my fleece hood on and which just as quickly flapped back down from over my head as the wind whipped at it.  Part of this time was spent contentedly watching as the shadow of my hair danced on the grass and rock at my feet as the easterly wind blew in.

These surveys took over two hours to complete, the distance from one to the other was almost negligible and sometimes involved only a minute’s walk from one bump to the next.  The highlight was the vertical cliff face of the summit that is given a 479m spot height on current Ordnance Survey maps.  This sprang up in welcome surprise and although I considered scrambling up it I chose a more circumspect route taking a downward slant before the upward part could begin.

Snow capped Yr Wyddfa

All of these eleven surveys centred round the small mountain lake of Llyn y Drum which squatted penned into the landscape almost forgotten amongst the crags and bumps.  Having completed these surveys I lost height heading toward the last hill of the day; Craig y Garreg Lwyd which had been on the horizon standing rounded and beckoning for an age, its bwlch proved a boggy affair which had a stunning backdrop as compensation.

Llyn y Drum with the high Moelwynion beyond

Llyn y Drum with Manod Mawr in the background
Gathering data at the critical bwlch of Craig y Garreg Lwyd

Only one survey remained which proved to be the nineteenth of the day, and this was at the summit of Craig y Garreg Lwyd.  I walked up to its fairly large cairn and positioned the Trimble on a flat rock on top of the cairn and measured the offset to its base before pressing ‘Log’ and waiting the customary five minutes for data to be gathered.

Gathering data at the summit of Craig y Garreg Lwyd

My walk out was back to the connecting bwlch and downward following a vehicle track on the moor to my inward route next to the shore of Llyn Morwynion.  Looking back up toward where I had been, standing still like, waiting against wind, chilled and happy, looking and mind wandering, I felt a contentment of self, happy in the knowledge that the hills at given again, as they often do, ever majestic they stand whilst we pass through.  It had been another good day.


Y Garnedd and Carreg y Foel Gron above the waters of Llyn Morwynion


Survey Result:


Bryn Glas

Summit Height:  415.6m (converted to OSGM15)

Summit Grid Reference:  SH 73505 42086

Bwlch Height:  393.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 73647 42052

Drop:  21.7m (400m Sub-Pedwar status confirmed)

Dominance:  5.22%



Pt. 483.6m

Summit Height:  483.6m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SH 73541 42812 (summit position confirmed)

Bwlch Height:  449.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 73778 42825

Drop:  34.4m (Pedwar status confirmed)

Dominance:  7.12%



Pt. 474.4m

Summit Height:  474.4m (converted to OSGM15)

Summit Grid Reference:  SH 73258 42938

Bwlch Height:  460.6m (converted to OSGM15)

Bwlch Grid Reference:  SH 73295 42889

Drop:  13.8m

Dominance:  2.90%



Craig y Garreg Lwyd

Summit Height:  473.4m (converted to OSGM15, Trimble GeoXH 6000)  473.8m (converted to OSGM15, Leica GS15) (significant height revision)

Summit Grid Reference:  SH 73044 42742 (Trimble GeoXH 6000) SH 73047 42746 (Leica GS15)

Bwlch Height:  443.5m (converted to OSGM15, Trimble GeoXH 6000) 443.6m (converted to OSGM15, Leica GS15)

Bwlch Grid Reference:  SH 73222 42804 (Trimble GeoXH 6000) SH 73224 42803 (Leica GS15)

Drop:  29.9m (Trimble GeoXH 6000) (Pedwar reclassified to 400m Sub-Pedwar) 30.2m (Leica GS15) (400m Sub-Pedwar reclassified to Pedwar)

Dominance:  6.32% (Trimble GeoXH 6000) 6.37% (Leica GS15)



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





1 comment:

Alex Cameron said...

Interesting that Craig y Garreg-lwyd has now been demoted seeing as I filmed a scene on the summit for the Pedwarau video. Oh well I'll need to head up again and chuck a few more rocks on the cairn ;).