Thursday, 21 May 2015

Mapping Mountains – Trimble Surveys – Pegwn Mawr

16.05.15  Foel (SO 067 786)  

Foel (SO 067 786)
Foel stands as an elongated ridge running north to south above the road between Llaethddu (SO 068 800) and David’s Well Bridge (SO 059 786).  It has footpaths encircling it all except for its western side which had the road running its full length.

Its bwlch is positioned to the south-east of its summit and connects with another Pedwar, named Castle Bank.  In January 2013 I’d almost visited this hill when out on a walk with Mark, we’d already visited Brondre-fawr Hill, Castle Bank and Moel Dod and daylight was running out, so it was left for another day.

I parked at SO 064 780 opposite a house where at least one car can safely be pulled off the narrow road, there is another option for parking on the grass verge close to a gate that gives access onto a track which gains height around the southern flank of this hill.

The inward track contouring around the southern flank of Foel
By now the afternoon was pleasant when sheltered from the brisk wind that still blew across the tops; sunshine sparkled the landscape and gave an appealing mood to the walk.  I followed the track up toward a ruined old building, which now has a large barn built into the hillside behind it.

Passing an old building on the way toward the critical bwlch of Foel
I wanted to survey the bwlch for this hill first and having walked quietly past a group of cows and their young calves I clambered into the field where the critical bwlch seemed to lay.  Ten minutes later and I was still wandering around trying to judge the ups from the downs, I decided to gather two data sets in the valley to valley direction and as the Trimble imperceptivity crept down to its required 0.1m accuracy before data can be logged the cattle ventured into the field behind me and I sat on an earthen bank and ate some butties. 

It took a long time for the Trimble to attain its accuracy, but once it had, I pressed ‘Log’ and retired to my seat and waited patiently.  The second data set was taken from a small enclosed area of land that seemed to have been part of a track leading from one hill to another.  Again I waited patiently with the wind at my back, eventually the required accuracy was reached, ‘Log’ was pressed and I sat down again and waited until five minutes of data were gathered.  During these two surveys I watched a tractor on the opposite hillside ploughing the land, I was in full view of the farmer and wondered what he was thinking as this person walked seemingly aimlessly around a field and then sat for minutes on end, occasionally scampering toward a small yellow thing before scampering away from it again.

The Trimble position for the second bwlch data set
Once the data were stored I walked up the adjacent field to a gate which gave access to the top of Foel.  The wind blew when I crested its summit ridge; I assessed the high point from a number of directions before choosing the spot for the Trimble.  As it gathered data I looked out on the wind turbines on Pegwn Mawr to the west as their blades skimmed around.

Looking toward Pegwn Mawr
Gathering data from the summit of Foel
Once the Trimble was packed away I followed the hill’s broad southerly flank down to the track I had followed on my inward route, and rejoined the narrow road back to my car.  Only one walk remained for my afternoon and that in the proper sense, really wasn’t a walk, it was a survey of the water level of Llyn Clywedog as I wanted to obtain a drop value for Bryn y Tail, this hill is another Pedwar and I had surveyed the road that crosses the Reservoir and the land below it last year, but I had not surveyed the height of the water level in the Reservoir.  Hopefully I wouldn’t fall in!

Survey Result:


Summit Height:  460.4m (converted to OSGM15)

Summit Grid Reference:  SO 06751 78601

Bwlch Height:  415.6m (converted to OSGM15)

Bwlch Grid Reference:  SO 07101 78330

Drop:  44.8m

Dominance:  9.73%

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

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