19.07.20 Foel Fawr (SH 728 392), Foel Fawr (SH 726
394), Pt. 501.4m (SH 730 397) and Pt. 499.9m (SH
731 395)
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| Foel Fawr (SH 728 392) |
Between Llyn Trawsfynydd
to the west and Llyn Conglog Mawr to the east lie a compact group of hills with
Graig Wen (SH 739 394) the highest. These
hills are open with few fences and are bounded on the north by an invasive
conifer plantation. The summits overlook
many small lakes and pools, each adding depth of variety and perspective to the
landscape. These hills seldom draw me
back, but on the times I’ve visited they never disappoint.
Today I met Aled for our
first walk together since earlier this year in January. Covid-19 and its affects have altered many
things and one was the travelling restriction which impacted greatly upon
visiting the hills. With this
restriction now lifted it was good to be out again with a number of surveys
planned.
We met close to Llyn
Trawsfynydd and soon had our cars parked at the beginning of the track leading
to Llyn yr Oerfel. Behind the lake our
first hill of the day; Foel Fawr, rose in a great bulk of steepening
grass. The continuation of the track led
to the Braich-ddu Quarry with a vehicle track on the near moor leading us
higher toward the southern ridge of Foel Fawr, and the first of its two 528m twin
map heighted summits.
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| The two Foel Fawr summits with the old prioritised summit position on the left and the new higher summit on the right |
This summit has a
marvellous backdrop with the higher Eryli peaks lined one after another with
the Moelwynion prominent and the distinctive profile of Moelwyn Mawr and
Moelwyn Bach rising directly behind the large cairn atop the second and more
northerly of the hill’s twin map heighted summits. Once data were gathered and stored from the
first summit and the connecting bwlch we were soon beside the cairn with the
Trimble again gathering its allotted data.
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| The lower cairned summit of Foel Fawr with Moelwyn Bach and Moelwyn Mawr as backdrop |
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| Gathering data from the summit of Foel Fawr |
The main objective of
the walk was to visit and hopefully survey a forested hill that is given a
small 500m ring contour on the Ordnance Survey 1:25,000 Explorer map and a 504m
spot height on Magic Maps and on the mapping on the WalkLakes website. Its connecting bwlch is placed in a rather
unsavoury and daunting looking bog. We
had come prepared with a series of ten figure grid references and hoped to take
data from each point.
As the Trimble gathered
data from the first position, which like all others was in a watery realm, Aled
headed in to the conifers armed with an axe.
I then spent the next ten minutes listening to the quiet beep emanating
from the survey equipment as each data point was collected and the ever distant
crack of branches as Aled carved a way uphill toward the summit. As he emerged back close to the bwlch he
reported that the lower slopes were relatively easy but the higher slopes leading
toward the summit were a mess, with numerous wind-blown trees now felled at all
angles across the ground.
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| Gathering data at the first bog survey |
Following Aled in to the
confines we veered to the right and kept below the wind-blown trees which
proved an easier route than the one Aled had investigated on his preliminary
foray. Just before the felled trees were
encountered we came upon an unexpected crag, which is quite substantial and now
left immersed in the confines of regimented conifers.
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| The crag leading toward the summit of the new forested Uchaf |
The assault course now
started, it was never too difficult and soon we had clambered our way over,
under and through numerous trees and found the summit just beyond a small area
that had direct sunlight breaking through the forest and a view of the sky
which gave hope for data collection. The
high point consisted of a flat rock and we quickly devised a system to measure
the offset between it and the Trimble placement with it sitting atop my rucksack
which was on a conveniently felled tree giving it elevation above its
surrounds. Considering where we were it
achieved its 0.1m accuracy level before data should be logged relatively
quickly and we sat and chatted as it gathered its allotted data. Reversing our inward route through the
wind-blown felled trees we emerged in to the upright mature forest and
contoured around the lower part of the plantation aiming for our next survey in
the watery bog. By keeping in the forest
we avoided the impossibility of bog walking which may have proved hazardous!
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| Aled at the summit with the Trimble |
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| Gathering data on the summit area of the new forested Uchaf |
The ten figure grid
reference Aled produced for the next survey which was listed as the connecting
bwlch for the forested hill, was in the centre of a pool, which made me smile when
I pinpointed it on the mapping on the OS Maps website. As we emerged out of the conifer plantation
we were back in the bog, thankfully a semblance of dryish ground led around its
reed infested quagmire toward the pool.
I proceeded to set the Trimble up atop my rucksack on a large sponged
grass tussock, measured the offset between its internal antenna and the ground at
its base and as it beeped away collecting data, I lay across two tussocks close
by, and considering the surrounding conditions I remained remarkably dry.
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| Gathering data beside the small pool |
The next point to survey
was a 499m map heighted top and Aled encouraged its bwlch to also be
surveyed. This proved to be beside a
series of pools glinting blue in the late afternoon sunshine. Once bwlch data were gathered and stored we
headed for the last summit and sat in the warming conditions as another five
minutes of data were gathered.
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| Beside the small lake heading toward the bwlch that connects with Pt. 499.9m |
All that remained was
another investigation of the bog to our immediate east which connects with Foel
Fawr. We’d already taken two data sets
from its waters and with an elevated view we now decided to take two more, one
from between the two main large pools which are connected via smaller channels
and the last from the edge of the southerly pool. Considering how horrendous this looked it
proved relatively easy to accomplish.
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| The penultimate bog survey |
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| The route back to the awaiting cars |
All that remained was
the walk out following a track-bed contouring around the southern ridge of Foel
Fawr, which in time connected with our inward route and led back to the track
leading to Llyn yr Oerfel.
Postscript:
Since surveying these hills full LIDAR coverage is now
available. The LIDAR (Light Detection & Ranging) technique
produced highly accurate height and positional data that is now freely
available for England and Wales. Consequently the numerical details
for these hills have been analysed using this technique, and where appropriate
LIDAR has been used in preference to that produced by the Trimble.
Survey Result:
Foel Fawr
Summit Height: 528.6m (converted to OSGM15) (confirmed as
higher than the top positioned at SH 72621 39476)
Bwlch Height: 485.5m (converted to OSGM15)
Bwlch Grid Reference: SH 73074 39525
Drop: 43.1m
Dominance: 8.15%
Foel Fawr
Summit Height: 527.5m (converted to OSGM15) (confirmed as
lower than the top positioned at SH 72872 39284)
Summit Grid Reference: SH 72621 39476
Bwlch Height: 515.5m (LIDAR)
Bwlch Grid Reference: SH 72742 39451 (LIDAR)
Drop: 12.0m (Trimble GeoXH 6000 summit and LIDAR bwlch)
Dominance: 2.28% (Trimble GeoXH 6000 summit and LIDAR bwlch)
Pt. 501.4m
Summit Height: 501.4m (converted to OSGM15, Trimble GeoXH 6000)
Summit Grid Reference: SH 73011 39784 (Trimble GeoXH 6000)
Bwlch Height: 485.7m (LIDAR)
Bwlch Grid Reference: SH 73070 39636 (LIDAR)
Dominance: 3.13% (Trimble GeoXH 6000 summit and LIDAR bwlch)
Pt. 499.9m
Summit Height: 499.9m (converted to OSGM15, Trimble GeoXH 6000)
Summit Grid Reference: SH 73187 39525 (Trimble GeoXH 6000)
Bwlch Height: 490.0m (LIDAR)
Bwlch Grid Reference: SH 73453 39600 (LIDAR)
Drop: 9.9m (Trimble GeoXH 6000 summit and LIDAR bwlch)
Dominance: 1.98% (Trimble GeoXH 6000 summit and LIDAR bwlch)
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