03.06.18 Allt y Derw (SN 873 834) and Fuches (SN 866
836)
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| Fuches (SN 866 836) |
When leaving home the
sky had rolled in a smooth light grey, down and across near hill tops, although
a sign of summer lightness when delicate mist formations follow high hill
valleys, it still gave a feeling of oppression and I hoped that clearer
conditions could be found further west.
Thankfully patches of
blue appeared as I drove past Llanidloes and nearing my destination the hills I
wanted to visit were clear of mist, with their higher neighbours still bathed
in summer clag.
I’d visited Allt y Derw
and Fuches in November 2003 and surveyed from the connecting bwlch eastward to
where the 449m spot height appears on the ground and concluded that the summit
of Allt y Derw was approximately 3ft higher than this point giving a 99ft /
30.3m drop value, and that Allt y Derw and Fuches were about equal in height,
concluding that each should be listed as P30s and included in what is now the Y
Pedwarau, with Fuches the prioritised higher hill based on its larger 450m
uppermost contour ring.
Over recent times the
status of Fuches has changed due to LIDAR analysis, and this was then
questioned as the summit position produced by LIDAR did not match that from
on-site visits. As each hill is similar
in height, which was higher also affected their respective bwlch positions and
drop values. My intention today was to
survey both hills and try my utmost to clarify the situation.
I approached from the
south-east having left my car at the start of a wide track just off the narrow
lane that makes its way across these hill ridges. As I gained height the forested summit of
Fuches came in to view with slight signs of sunlight striking its slopes and
having a deep grey sky above.
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| The first hint of sunlight on the forested slopes of Fuches |
The high point of Allt y
Derw was easily identified and consists of grass beside a fence; I set the
Trimble atop my rucksack, measured the offset between its internal antenna and
the ground below and waited for 12 minutes of data to be gathered.
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| Gathering data at the summit of Allt y Derw |
Once the Trimble was packed
away I continued toward Fuches and the connecting bwlch between these two
hills. Arriving at the bwlch the sun had
burnt off any lingering mist and the land became bathed in clearer heat
compared to the mugginess of my ascent.
The critical point of
the bwlch lay close to a fence and adjacent to the large conifer plantation that
swamps the whole of Fuches, and another 12 minutes of data were gathered.
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| Gathering data at the critical bwlch of Fuches |
When I visited these
hills in 2003 I found a narrow path through the conifers that led up the
north-eastern ridge of Fuches to its high point, this is now a relatively wide
track used by trail riders and accessed from a forest track, and as I headed
from the connecting bwlch toward this track a mountain biker appeared, we
stopped and chatted, David Hirst lived locally and kindly confirmed the access
point for the upward track.
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| David Hirst |
The track led up as a
ribbon of bedrock against the greened sides of moss and wooded growth with
overbearing and regimented conifer trees either side. When reaching the summit area I paced 12
metres between what I judged to be two potential high points for the track,
with ground between each being relatively flat.
I chose which I judged to be the higher and set the Trimble up.
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| The track leading to the high point of Fuches |
Before activating the
Trimble I took a series of measurement offsets as the track had been gauged out
of the hill to the bedrock and ground either side was slightly higher, with
that on the south-easterly side looking the higher.
Once the Trimble was
activated I expected a long wait until it achieved its 0.1m accuracy level
before data should be logged, however this magical figure appeared on the
screen within about 15 minutes and I quickly pressed ‘Log’ and scampered back
down the track and waited for data to be gathered.
I wanted a minimum ten
minute data set from the summit of Fuches and as long as the Trimble did not
screech, which is a sign that the accuracy is not being attained, I thought a
longer data set was achievable, and eventually closed the equipment down after
28 minutes of data collection.
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| The Trimble set-up position at the summit of Fuches |
During this wait I stood
on the track, listened for any rogue trail bikers and let my mind wander to all
manner of things and places. I’ve found
this waiting time can be a thought provoking process when one’s mind can either
drift or be concentrated on matters at hand; it is a time to be savoured and
appreciated, although I also have to admit that there is a time limit to such
waits where the balance of appreciation is tipped to when boredom sets in.
Once data were stored
and after taking a few photos and packing the Trimble away I retraced my inward
route back to my car. The next hill
would tip me over to when boredom set in as I waited on its summit for nearly
90 minutes, it was another hill whose summit position and current status needed
checking against data produced via LIDAR analysis, the name of the hill is
Fynach Fawr.
Survey Result:
Allt y Derw
Summit Height: 450.0m (converted to OSGM15)
Summit Grid Reference: SN 87314 83429
Bwlch Height: 375.7m (LIDAR)
Bwlch Grid Reference: SN 86409 83857 (LIDAR)
Drop: 74.3m (Trimble summit and LIDAR bwlch)
Dominance: 16.51%
Fuches
Summit Height: 449.3m (converted to OSGM15) (significant height revision)
Summit Grid Reference: SN 86623 83656
Bwlch Height: 419.1m (converted to OSGM15)
Bwlch Grid Reference: SN 86997 83837
Drop: 30.2m (400m Sub-Pedwar reclassified to Pedwar)
Dominance: 6.71%
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