Saturday, 9 April 2016

Mapping Mountains – Trimble Surveys – Rhos


05.04.16  Moelfre Uchaf (SH 898 716)  

Moelfre Uchaf (SH 898 716)

On my way to visit the two hills that make up Tre Pys Llygod (SH 886 686 and SH 894 687) I stopped to survey the critical bwlch of Moelfre Uchaf, whose summit I wanted to visit later as part of four separate walks planned for the day.  The critical bwlch of Moelfre Uchaf is positioned close to a road junction high in the hills that take in its own name and that of Mynydd Hiraethog.

The road junction is a crossroads with the west – east branch taking in the A 548 between Llanrwst and Llangernyw, whilst the southern branch is a minor lane and the northern branch is a part of the B 5113 as it heads toward Colwyn Bay.  Interpolation of map contours suggests that the critical bwlch is positioned just on this northern branch; the B 5113.

I’d investigated this area in a Google Car and thought the critical point to be on the road and decided that the safest way to survey it was to position the Trimble on top of my car’s roof.  After parking the car I walked up the B road and then the minor lane looking for the point where the hill to hill traverse met, I then looked at the meeting of the valley to valley traverse from different positions, having chosen the spot I re-positioned my car, set the Trimble up, took a measurement offset and stood in the morning’s sunshine until five minutes of data were gathered.

Using a car as an improvised tripod

Gathering data at the critical bwlch of Moelfre Uchaf

Once the equipment was packed away I continued toward Tre Pys Llygod, surveyed its two hills and their bylchau and then drove toward Moelfre Uchaf.  This hill is the highest in the northern part of Mynydd Hiraethog and one that until today had bi-passed my bagging exploits.  I parked where a track branches off from a minor lane at SH 889 712 and walked down the road to where a gate gave access on to the closely cropped grass of the hill’s southern slopes.

The trig atop the summit of this hill could be seen stretching off to my north-east at the end of the hill’s rounded western ridge.  It was an easy contented plod up the southern slopes using gates to gain access to each fenced enclosure where sheep and their lambs grazed in the afternoon sunshine.

The trig pillar on the summit of Moelfre Uchaf

As I approached the trig I knelt on the ground and pinpointed the highest bit of land on the western side of the trig, I did likewise on the north, east and south sides, and happy with my chosen placement I set the Trimble on the ground and away it went doing its Trimbling as I stood a safe distance from it.

Gathering data at the summit of Moelfre Uchaf

Leaving the summit I re-traced my route back to the car and then studied the map for my onward journey to Moel Fodiar; a 390m Sub-Pedwar whose status needed checking.


Survey Result:


Moelfre Uchaf

Summit Height:  395.8m (converted to OSGM15, Trimble GeoXH 6000) 

395.8m (converted to OSGM15, Leica RX1250)  (390m Sub-Pedwar status 

confirmed)

Summit Grid Reference:  SH 89798 71601

Bwlch Height:  251.5m (converted to OSGM15, Trimble GeoXH 6000) 251.5m 

(converted to OSGM15, Leica RX1250)

Bwlch Grid Reference:  SH 82775 63864

Drop:  144.3m (Trimble GeoXH 6000) 144.3m (Leica RX 1250)  (Submarilyn 

status confirmed)

Dominance:  36.45% (Lesser Welsh Dominant status confirmed)



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





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