Thursday, 12 November 2015

Mapping Mountains – Trimble Surveys – Moel y Gamelin

20.10.15  The Pimple (SJ 299 472)  

The summit of The Pimple (SJ 299 472)

My last two walks had explored the remains of land that was once spoil waste from the Bersham and Hafod Colliery’s respectively, and this walk was similar as just to the west of Bonc yr Hafod is another hill whose map details suggest that it was made of mine spoil dug from the ground.  This hill is also of interest as the current Ordnance Survey 1:50,000 and 1:25,000 maps have a 23m height difference for their summit spot heights with the 1:50,000 giving 131m and the 1:25,000 giving 154m, I thought a little Trimbling should be able to sort this out.

I parked on a housing estate at approximately SJ 298 468 which is to the south-west of the summit and walked down the road to a gate / stile giving access to a public footpath in a field, where two horses were contentedly grazing and one sauntered over to make closer inspection of their new visitor.

The critical bwlch for this hill is positioned westward of the summit in a valley that is narrow on the hill to hill traverse and elongated on the valley to valley traverse, without the aid of optical implements I knew that I may have to take a series of data sets to then compare heights, and the first of these was beside a hedgerow where interpolation suggests the bwlch to be placed.

Beyond was a foot stile and cropped grass leading to a house, as I wanted to ask about the name of the hill I headed toward it and Glenys Valentine came out to meet me, Glenys is aged 77 and proved a lovely woman to speak with, within a few minutes her son; Kevin, pulled up and the three of us chatted away for 15 minutes or so, they know the mound at the top of their field as ‘The Pimple’ and although Glenys can speak Welsh and Kevin had a smattering of the language, it was the English term they used and knew the hill by, this had been used by the family for a number of generations.  I also asked if I could survey a number of points close to the house and explained what I was doing.  They both gave me permission to do so and Kevin suggested the best way to take to visit the summit.

Over the next hour I happily gathered a further four data sets from various points on the valley to valley traverse, this was complicated by a mound near to the house and ground either side joining and continuing down valley. 

Gathering data from the critical bwlch of The Pimple

Once I was satisfied that sufficient data sets had been gathered from the area of the bwlch I headed up the hill to the summit of The Pimple, this is as its name suggests; a small mound perched on top of another larger one, all is land that was once mine spoil, it is now grassed over.  As the Trimble gathered data I looked over toward the adjacent field where the 154m spot height appears on current maps, and once the Trimble had done its stuff I clambered over the fence and marched to the top of the ploughed and smoothly rounded field.

Gathering data from the summit of The Pimple

It wasn’t difficult to judge where the summit was placed and the Trimble was soon perched on top of my rucksack gathering its allotted five minutes of data.  Thankfully all was quiet hereabouts as where the summit is situated was just out of sight of many of the surrounding buildings.

Gathering data from the high point in the adjacent field

Once data were gathered I packed the Trimble away and clambered back over the fence, walked down the hill to the grassed valley and back to my car.

Survey Result:

Summit Height:  153.5m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SJ 29984 47262 (summit relocation confirmed)

Bwlch Height:  128.3m (converted to OSGM15)

Bwlch Grid Reference:  SJ 29752 47350

Drop:  25.2m (100m Sub-Twmpau addition confirmed)

Dominance:  16.44%

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

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