Sunday, 5 June 2016

Mapping Mountains – Trimble Surveys – Mynydd Preseli


14.05.16  Carn Trefeiddan (SM 729 250)

Carn Trefeiddan (SM 729 250)

Having been deposited safely on dry land after visiting The Smalls, Emsger (South Bishop) and Daufraich with Venture Jet, we wandered up the steps leading from the RNLI Lifeboat station at St Justinian’s west of St David’s to our awaiting cars, the weather had improved since the still but grey skied conditions of this morning, as the sun now shone down with a pleasant cooling slight northerly breeze bringing welcome vividness to the colour on the surrounding land.

People immediately laid plans for the remainder of the day and an obvious objective was Carn Trefeiddan, which at a map heighted 72m is a P30 just to the east south-east of where our cars were parked.  Remarkably Rob hadn’t visited this small hill, and neither had Adrian, it had also been on my wanted list for the weekend, so as Rob and Adrian wandered up the road to their cars, I quickly converted my walking trousers to shorts and gathered all necessary equipment and a few minutes later we were walking up the road with Ayako deciding to stay at the car until Adrian’s return from the hill.

After only a short distance up the road we took to a field directly below the summit of the hill.  Ahead was a good looking summit with grass and gorse interspersed amongst good Pembrokeshire rock.  On our way toward the bottom bit of rock we came across a memorial stone with an interesting inscription, one that no doubt was heart-felt, but still rather unusual in its chose of words.

Memorial on the north-western slopes of Carn Trefeiddan - it's worth reading it

Beyond the memorial bluebells sprang out of a carpet of grass, their blues matching well with the greens.  A bit of hand on rock was needed to clamber up and on to the ridge crest of the hill, and from here it was only a short walk to the high point which consisted of rock.

Rob and Adrian on the way up Carn Trefeiddan

Once at the summit I aligned the internal antenna within the Trimble to the high point of the hill and balanced its back end on my rucksack to give the equipment a semblance of being horizontal, and off it went collecting its allotted five minutes of data.

Adrian and Rob at the summit of Carn Trefeiddan

The Trimble set-up position at the summit of Carn Trefeiddan

Afterward we retraced our inward route to the memorial stone where I headed toward the hill’s connecting bwlch and Rob and Adrian headed back to their cars, having arranged to meet at 5.30pm in Porthgain as Rob quite fancied investigating a tidal island named Ynys Fach, this proved rather exciting and will be detailed in the next blog post.

As we’d looked out from the summit of Carn Trefeiddan we followed the lay of land from Pwll Trefeiddan; a substantial lake to the east of the summit, as its reed infested and no doubt boggy adjacent land headed up the hill to hill traverse to meet its high point somewhere near a meeting of road and track close to where a 39m spot height appears on Ordnance Survey maps.  It was here that I headed.

Once beside the road and tracks I assessed the lay of land and decided that the best and most convenient place to set the Trimble up was on top of a milk churn which was positioned on top of a white washed platform beside the minor road, this appealed to my sense of fun as I’d never surveyed the top of a milk churn before.

As the Trimble gathered its data Rob drew up in his car, we chatted for a few minutes before he sped off to visit Carn Llidi, which is an impressive looking hill situated just to the north.

Gathering data at the top of a milk churn at the bwlch of Carn Trefeiddan

All that remained was for the last of the Trimble’s 300 data points to be stored and for the equipment to be switched off, packed away and for the pleasant walk back to my car in the afternoon sunshine.  Next stop Porthgain and the excitement of a scramble down a cliff to a tidal island.


Survey Result:


Carn Trefeiddan

Summit Height:  73.7m (converted to OSGM15)

Summit Grid Reference:  SM 72930 25042

Bwlch Height:  38.2m (converted to OSGM15)

Bwlch Grid Reference:  SM 73054 25388

Drop:  35.5m (30-99m Twmpau status confirmed)

Dominance:  48.20% (Lesser Dominant status confirmed)







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