Tuesday, 24 December 2019

Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

18.09.19  Foel Uchaf (SJ 046 590), only bwlch surveyed

At least this bwlch survey would give me a semblance of a walk, however short in time and distance.  As the day consisted of roadside bwlch surveys I was by now used to pulling my car up at a convenient parking place and sauntering a few metres either to the position of the bwlch, or putting the Trimble on the roof of my car with it positioned directly over where I judged the respective bwlch to be positioned.  But the surveying of this bwlch entailed a walk down a road and in to a field which brought a semblance of exercise to the day’s proceedings.

The bwlch of Foel Uchaf

This survey formed a part of a roadside bwlch surveying trip and was squeezed between the bwlch surveys of Moel Yta and Moel Fama and was the seventh of nine such surveys planned for the day.

I’d already driven a digitised Google car on the minor lane to the north-west of this hill’s summit and found a convenient place to park, and 24 hours later I was there, safely parked with rucksack on my shoulders and Trimble in hand walking down the continuation of the minor road to a gate that gave access in to the field where one of the options for this hill’s bwlch is positioned.

The field is used for grazing sheep and a few sauntered around munching away as I made my way to what proved to be a relatively tight bwlch that was easy to pinpoint as I assessed the lay of land, and within a few minutes the Trimble was in position atop my rucksack gathering allotted data.

Gathering data at the bwlch of Foel Uchaf

The 5m contours on the OS Maps website indicate that another positional option for the bwlch is situated further west from the favoured position where the Trimble was now gathering data from.  Therefore, once data were stored I closed the equipment down and headed to the westerly perimeter of the field to the boundary hedge where a second data set was gathered.  This second position was adjacent to the minor road that heads south toward the Afon Clywedog. 

For the second data set I placed the Trimble on a fence post and noted the measurement offset, however this placement was above the adjacent road, which after the survey I visited and took another measurement to the approximate position of the ground at the base of the fence post.

Gathering data at the second bwlch set-up position

I then visited the field on the other side of the minor road and as this was on the hill to hill traverse and looked level if not slightly lower than the road, I took a third data set with the Trimble set up beside a track leading westward around the southern confines of Moel Yta.

Gathering data at the third bwlch set-up position

Once data were stored I made my way back to the car, checked the map and headed toward Rhuthun (Ruthin) and the continuation on the A525 road to the penultimate bwlch survey of the day; that for Moel Fama. 

Survey Result:

Foel Uchaf

Summit Height:  372m (spot height)

Summit Grid Reference:  SJ 04697 59012 (hand-held GPS via DoBIH)

Bwlch Height:  285.7m (converted to OSGM15)

Bwlch Grid Reference:  SJ 03828 59515

Drop:  86m

Dominance:  23.20%


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