Monday, 29 December 2014

Mapping Mountains – Trimble Surveys – Pen Llŷn



28.12.14  Clip y Gylfinhir (SH 223 284)   

Clip y Gylfinhir (SH 223 284)
As Mark drove toward the western tip of Pen Llŷn (Lleyn Peninsula), Aled talked about a hill that stood a chance of becoming a P30, it was positioned just to the south of Mynydd Rhiw.  Although our plans were not set firm we had discussed a route between three hills that was feasible this time of year, and as the skies were bathed in blue it would only be lack of daylight hours that curtailed this plan.  However, spontaneity can be fun and soon Aled was directing Mark through the narrow network of lanes toward the car park immediately below Clip y Gylfinhir.

Clip y Gylfinhir (one translation of the name is the Curlew’s crag) is listed as a 200m Sub-P30 with its bwlch contouring and 270m summit spot height implies that it has 28m – 29m of drop.  As Mark drove up the last icy road toward the car park the hill loomed up conically shaped and well proportioned.

Once parked, Aled headed into the heather to assess the direction of the bwlch as it swings down from Mynydd Rhiw and ascends from the small community of Rhiw.  The small car park is also the hub for a meeting of tracks; these at least gave perspective towards the elevation of the bwlch and broke the heathery slopes.

As Aled assessed the bwlch Mark headed into the heather to photograph the hill without its adjacent wireless and radio transmitting mast in the scene, he then headed up the hill.

Mark on the summit of Clip y Gylfinhir
The point Aled had reached in the heather was good to pinpoint the critical bwlch but it would only be from the summit where we would have an aerial view of the scene.  Not wanting to keep Mark waiting a spot close to the meeting of tracks adjacent to the earthen car park was chosen and I set the Trimble up.

Once five minutes of data were collected we headed up the hill to join Mark on the summit.  From the car park a small path veers away from the access road to the transmitting mast and heads straight up the hill, I left the path to take photos of Aled as he gained height on steepening broken ground.

Aled on the ascent of Clip y Gylfinhir
The summit area consists of a number of embedded rocks, the highest being easily identified, and as the Trimble had its internal antenna aligned to the high point of the hill and started to log data I stood back and took in the view.

Gathering data at the summit of Clip y Gylfinhir
To the north the continuation of the main track from the car park headed up to the summit of Mynydd Rhiw, to the west the agricultural lowlands culminated in the last upthrusts of hills before the end of Wales and Ynys Enlli (Bardsey Island), the immediate eastern horizon was dominated by the great sweep of Porth Neigwl (Hell’s Mouth) and away inland stood a line of hills which were all snow-capped.

Mynydd Rhiw (SH 228 293)

The lowlands of the western Llŷn leading to Ynys Enlli

Porth Neigwl (Hell's Mouth)

Yr Wyddfa dominating the central view
After packing the Trimble away we descended the hill’s southern slopes toward the transmitting mast where I walked into the heather and gorse next to the paved access road to try and get a photo of Mark and Aled against Clip y Gylfinhir.

Heading toward the bwlch
From the summit was had a good view of the lay of land around the area of the bwlch and could easier follow the southerly ridge of Mynydd Rhiw as it heathered its way down toward the connecting land of Clip y Gylfinhir.  From the vantage point of the summit the hill to hill traverse looked as if it headed into an adjacent field toward a metal cattle feed which was conveniently placed and gave us a point to use for reference.

It was this hill to hill line that we now headed for, judging that the low point was on the heathery side of a double fenced and walled boundary and probably not in the closely cropped grassy adjacent field; the Trimble was set up and soon achieved its required 0.1m before it began to log data.

The set up position for the second data set
When I arrived back at Mark’s car we decided to head into Aberdaron for coffee and a bite to eat before revising our plans for further hills to the west.


Survey Result:

Clip y Gylfinhir

Summit Height:  266.1m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SH 22394 28474

Bwlch Height:  240.1m (converted to OSGM15)

Bwlch Grid Reference:  SH 22514 28524

Drop:  26.0m (200m Sub-Twmpau status confirmed)

Dominance:  9.77%
 


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

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