Monday, 17 July 2017

Mapping Mountains – Trimble Surveys – Carneddau

03.06.17  Pt. 650.9m (SH 702 657), Pt. 737.7m (SH 709 653) and Craig Eigiau (SH 713 654)

Craig Eigiau (SH 713 654)

The ridges of the Carneddau lend themselves to circular walks and the high car park in Cwm Eigiau is a convenient starting point with a number of options for either short or long walks, today we opted for the former as we had one in our midst who had a wonky knee and we also had a number of points to survey, both are not conducive to many miles on the hill.

The forecast was favourable with an odd rogue shower pushing northward predicted, otherwise winds were light and the temperature pleasant as we headed up the track from the car park having squeezed Aled’s van into the last remaining parking place.

Pen Llithrig y Wrach beyond Llyn Eigiau

The track contours around the northern part of Cefn Tal Llyn Eigiau and continues to the high lake of Melynllyn, and it was the grassy glacier moraine immediately to the east of this lake which was our main objective of the day, as Aled had analysed its northern bwlch and summit via LIDAR data, and the results were of sufficient interest to warrant surveying it and also its southerly bwlch with the Trimble.

Although I’d been on the Carneddau many times before I had never visited this lake and hadn’t continued on this track beyond the cut-off point where I had always previously headed to the summit of Craig Eigiau.

As we made steady progress toward Melynllyn the bothy of Dulyn came into view, a small roofed enclosure dominated by its mountain environment, it nestles below the lake of the same name and the black cliffs above, a testament to isolation. 

The isolated mountain bothy of Dulyn

Reaching Melynllyn gave us a good view up to the summit area of its glacier moraine, it was this that interested us as LIDAR data had given this hill a result tantalisingly close to 15m of drop from its northern bwlch to its summit, and at over 650m in height this hill stood a chance of being a new Uchaf as well as a new 2,000ft mountain, however LIDAR did not cover the area of the hill’s southern bwlch, with both bylchau being outflows we concluded that they must be close to, or equal in height.

Reaching Melynllyn

It didn’t take long to set the Trimble up at the northern bwlch and as this outflow was dry with the shoreline of the lake exposed and the water level relatively low, it meant that the bottom of my rucksack which was being used as an improvised tripod would remain dry.  Once ten minutes of data were collected we moved on to the summit.

Gathering data at the northerly bwlch

The Trimble set-up position at the northerly bwlch with Melynllyn and the cliffs leading to Foel Grach in the background

From below we could see the large erratic boulders scattered around the summit area and wondered if one of these was the high point, as we walked up the narrow path that follows the ridge of the hill and arrived at the summit we decided that the highest erratic and a point at ground level both needed surveying. 

The view from the northerly bwlch of the erratic boulders on the summit

As the Trimble gathered data from the top of the highest erratic we chatted and looked out across the lake, it proved a wonderful place to be and must be quiet at most times, as the lure and pull of the higher mountains encourage the throngs of people who visit this hill range.

Gathering data from the highest erratic boulder

Once data were stored from the top of the highest erratic, the Trimble was set up on top of my rucksack aligned with the position of an embedded rock at the ground level high point and a 0.11m measurement offset taken between its internal antenna and the embedded rock.

Gathering data from the high point at ground level

The fourth survey on this hill was at its southerly bwlch which LIDAR does not cover and we found this to consist of a reed invested channel, with its critical point easily identified the Trimble was set up and we waited for ten minutes of data to be gathered.  Once data were stored I took a few photographs, packed the equipment away and looked up at a steep grassed slope which Aled was already tackling.

Gathering data from the southerly bwlch

As we slowly headed up the slope the sky darkened and a brisk shower deposited its wet stuff, this soon passed and by the time we crested the ridge at the top of the slope the rain had headed north and the views west opened up.

The glacial moraine above Melynllyn

Surveying assistant

It was a day of surveying marginal hills for P15 Uchafion status, and the next candidate was a bump on the way between the higher 3,000fters and the rocky outcrop of Craig Eigiau.  This bump is given a summit spot height of 738m on Ordnance Survey maps and I had surveyed it with my wooden staff many a year ago in June 1998.

According to the map this bump has two options for its critical bwlch, both were surveyed with the more westerly option situated in a particularly wet place and which consists of a large boggy area, probably seldom visited, and yet retaining a beauty all to itself.

Gathering data at the westerly bwlch of Pt. 737.7m

The eastern face of Carnedd Llywelyn

The summit of the bump was relatively easy to pinpoint and once five minutes of data were collected we headed down to the bwlch between this hill and Craig Eigiau.  This bwlch consists of two small pools with the northerly one larger and circular shaped and the southerly one elongated.  As the northern part of the larger pool had an outflow we concentrated our efforts on the land leading to the southerly part of the smaller elongated pool, and again five minutes of data were gathered and stored.  Just one survey remained; the summit of Craig Eigiau.

gathering data at the summit of Pt. 737.7m
The bwlch of Craig Eigiau
Gathering data at the bwlch of Craig Eigiau

The summit of Craig Eigiau is a marvellous place and consists of a tapered large rock almost wave like in motion, with views toward Carnedd Llywelyn and the higher Carneddau.  We assessed this large rock for quite some time before deciding upon its high point and proceeded to wedge the Trimble in place with two small rocks.

Gathering data at the summit of Craig Eigiau

As the Trimble beeped away collecting the allotted 300 datum points I stood and soaked in the view, as this summit looks out as far as the Bryniau Clwyd and the hills of England beyond the wind turbines now in place close to the north Wales coast.  However, it was Creigiau Gleision and Pen Llithrig y Wrach that stood out as both were edged in sunshine highlighting their upper slopes.

Creigiau Gleision (SH 729 615)

Pen Llithrig y Wrach (SH 716 622)

After packing the Trimble away we followed the path on the grassed ridge down toward our inward track and back to Aled’s van.  It had been another good day on the hill. 

Survey Result:

Pt. 650.9m

Summit Height:  650.9m (converted to OSGM15) 
Summit Grid Reference:  SH 70272 65750

Bwlch Height:  638.0m (converted to OSGM15)

Bwlch Grid Reference:  SH 70321 65522

Drop:  12.9m (non 500m Sub-Uchaf status confirmed)

Dominance:  1.97%

Pt. 737.7m

Summit Height:  737.7m (converted to OSGM15) 
Summit Grid Reference:  SH 70973 65387

Bwlch Height:  728.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 70785 65210

Drop:  8.8m

Dominance:  1.19%

Craig Eigiau

Summit Height:  734.7m (converted to OSGM15, Trimble GeoXH 6000) 735.0m (converted to OSGM15, Leica RX1250)  
Summit Grid Reference:  SH 71314 65425 (Trimble GeoXH 6000) SH 71315 65425 (Leica RX1250)

Bwlch Height:  713.9m (converted to OSGM15, Trimble GeoXH 6000) 714.0m (converted to OSGM15, Leica RX1250)

Bwlch Grid Reference:  SH 71185 65473 (Trimble GeoXH 6000) SH 71191 65450 (Leica RX1250)

Drop:  20.8m (Trimble GeoXH 6000) 20.9m (Leica RX1250) (700m Sub-Twmpau addition confirmed)

Dominance:  2.82% (Leica RX1250 summit and bwlch)

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