Friday, 10 April 2015

Mapping Mountains – Trimble Surveys – Y Berwyn

10.04.15  Foel Wen (SJ 099 334) and Pt. 687.9m (SJ 102 330)  

Foel Wen (SJ 099 334)
The Berwyn on a mid-week day when the sun is shining and the paths relatively non-squidgy can be a delightful place to wander.  Today we had our sights on Foel Wen and its adjacent south-easterly neighbour; both had been given a variety of ten figure grid reference positions submitted to the Database of British and Irish Hills (DoBIH) and Graham had suggested that their respective summits needed surveying.

We met at 9.30am by a small bridge on a minor lane where two cars can be parked off the road, this is positioned at SJ 118 306 and is ideal for those wanting an extended walk around the Maen Gwynedd horseshoe.  Today we had lesser objectives peak and distance wise, but with a good forecast for dry and warm weather we were in no desperate rush and with the added weight of the surveying gear our pace around the hill was compromised.

We followed the lane up through two farm yards and out over a couple of fields to the southerly hillside of Mynydd Tarw, this hill is the first on the horseshoe if walked in an anti-clockwise direction.  It was a slow plod with a large rucksack, extra clothing and a tripod, but after an hour of walking uphill the hollowed out wind shelter at its summit came into view.

John and Graham at the summit of Mynydd Tarw
Beyond lay miles of moorland culminating in the rocky summit of Craig Berwyn (SJ 071 323) with a distinct path on the moor following the fence on the ridge line trying to bi-pass any bogs on the way, this path drops down to the connecting bwlch between Mynydd Tarw and the south-easterly top of Foel Wen before ascending the 22m to its summit.

Heading toward the summit of Foel Wen
By now we were experiencing a strong breeze, so much so that the predicted hottest day of the year seemed a distant reality.  We assessed the summit area of this south-easterly top before heading further west and the summit of Foel Wen.  When we reached this summit we quickly put on extra layers of clothing, including gloves and set the equipment up.  Graham looked through the level as John placed the staff in a number of positions working westward across the summit area, and I noted the readings.  The high point of Foel Wen proved to be at the far end of the summit ridge beside the remains of a small fence post.  As the Leica GS15 gathered 45 minutes of summit data we found a sheltered spot and lay in the heather chatting.  Before leaving we also collected five minutes of Trimble data.

Graham and John beside the Leica GS15 at the summit of Foel Wen
The remains of the old fence post marks the summit
Gathering data with the Trimble at the summit of Foel Wen
When the Trimble had gathered its allotted data I headed down to join John and Graham who were inspecting the bwlch between the hills before we headed back to the summit of the south-easterly top.  Very soon the staff and level were working wonders and pinpointing the high point of this hill to be approximately two metres from the small summit rock which is now almost overgrown by grass.  Another 45 minutes of data were collected by the Leica GS15 and five minutes of data with the Trimble.

Inspecting the bwlch between the two summits
John relaxing beside the fence
Using the staff and level to find the high point of the hill
Graham and John beside the Leica GS15 on the second surveyed summit
As the high cloud disappeared and the late afternoon sun broke out we backtracked toward the connecting bwlch of Mynydd Tarw and joined a slowly descending path that contoured around the southern flank of this hill back toward our inward route.  It had been a very enjoyable day on the hill and good to be out with John and Graham again after a few months absence.

Heading down from the hill
Survey Result:

Foel Wen

Summit Height:  690.7m (converted to OSGM15, Trimble GeoXH 6000) 690.7m (converted to OSGM15, Leica GS15)

Summit Grid Reference:  SJ 09934 33407

Drop:  59.0m (converted to OSGM15, Trimble GeoXH 6000)  59.0m (converted to OSGM15, Leica GS15, based on Leica summit and Trimble bwlch survey)

Dominance:  8.54% (based on Leica GS15 summit survey and Trimble GeoXH 6000 bwlch survey)

Pt. 687.9m

Summit Height:  687.9m (converted to OSGM15, Trimble GeoXH 6000) 687.9m (converted to OSGM15, Leica GS15)

Summit Grid Reference:  SJ 10232 33044

Drop:  21.6m (converted to OSGM15, Trimble GeoXH 6000)  21.6m (converted to OSGM15, Leica GS15, based on Leica summit and Trimble bwlch survey)

Dominance:  3.13% (based on Leica GS15 summit survey and Trimble GeoXH 6000 bwlch survey)

For details on the first survey of Foel Wen and Pt. 687.9m

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

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