09.10.15
Colfa Hill (SO 194 553)
Colfa Hill (SO 194 553) |
Colfa Hill is positioned
in the heart of Radnorshire where hills stand gentle and their heathered
summits are eased with a number of vehicle tracks that pass between valleys and
head toward their heights. Today we
wanted to visit Colfa Hill which had been on our radar for a couple of
years. The hill is listed as having 146m
of drop in the Marilyns list and c 147m in the 500m Twmpau list, this drop
figure is close to the 150m required for Marilyn status, and with a map summit
height of 532m and with the area of the bwlch having a 388m spot height on it
that is not centralised, there was an outside chance that the hill has more
prominence than currently listed.
We parked, having been
given permission to do so, at the end of the narrow road that passes to the
north and then east of Llyn Heilyn which is to the west of Llanfihangel Nant
Melan. It was good to be out with John
and Graham again and we soon had our boots on and walking up the track and
across fields following rights of way on old greened vehicle tracks.
John with level in hand on the way to Colva Hill |
The weather was set fine
for the day with blue sky and warmth for early October. Cresting a small intervening pastoral ridge
we continued down to cross the Gilwern Brook and then headed up the other side
toward the expanse of this hill’s bwlch.
Heading toward the bwlch which is on the left of photo with trees close to it |
Graham nearing the bwlch |
The spot height on this
bwlch appears at its eastern fringes, we started assessing this area from its
west and spent quite some time laying out rows of flags slowly working our way
east, with measurements taken to each five flagged row and noted. As we progressed the land that looked as if
it was rising toward our hill was in fact continuing to go downhill.
With each reading taken
by John with the level to the staff that Graham was positioning beside each
flag, the area of the bwlch was mapped out and its hill to hill and valley to
valley traverse slowly gave up its secrets.
I noted each height reading and after about 90 minutes we had pinpointed
where the critical bwlch was positioned, this was in a boggy runnel on the
eastern side of the area of the bwlch and proved to be approximately five
metres away from where the 388m spot height appears on the ground.
John operating the level |
Graham with the staff |
As John and Graham
assembled the Lerica GS15 for its hours’ worth of data collection I took a few
photos with the heightened autumnal colour accentuated by the low afternoon
sun. As the GS15 gathered its allotted
data we watched a farmer drive sheep down the opposite hillside, half an hour
later he drove toward us and I sauntered over for a chat; Ray Rogers proved
very friendly and gave out smiles in his thick Radnorshire accent, we talked
about the hills, their names and his sheep.
A few minutes later and John and Graham came over and we all nattered
away for ten minutes or so.
The Leica GS15 gathering data at the critical bwlch of Colfa Hill |
Graham and John with Ray Rogers |
Graham and John beside the Leica GS15 at the bwlch of Colfa Hill |
After one hour of data
were collected I positioned the Trimble on top of the GS15’s antenna and we
gathered a further five minutes of data, having taken a 1.086m measurement
offset between its internal antenna and the ground. Once all the equipment was packed away we
headed up the hill.
Gathering data with the Trimble at the critical bwlch of Colfa Hill |
Following one of the
many green vehicle tracks that criss-cross these hills, we gained height and
swung left (north) as we gained the south-west ridge of Colfa Hill, this track
led around Cwm Griffin and soon we were beside the trig pillar at the summit.
John approaching the summit of Colfa Hill |
This summit had already
been surveyed with an Abney level and the high point found to be approximately
seven metres north of the trig pillar.
As the afternoon sun sank ever deeper and a cooling chill enveloped the
land we took a series of measurements with level and staff and found that the
Abney measurement was spot on. Soon
afterward the Leica GS15 was set up and gathering its data.
Surveying for summit position on Colfa Hill |
Graham and John beside the Leica GS15 at the summit of Colfa Hill |
Once an hour of data
were collected the Trimble GeoXH 6000 was set up on its draughts board and sat on
top of the tripod that had previously supported the Leica equipment and
gathered its five minutes of data.
The Trimble gathering data at the summit of Colfa Hill |
The Leica and Trimble set-up position at the summit of Colfa Hill in relation to where the trig pillar is positioned |
All that remained was to
pack everything away and retrace our steps down the hill. Passing over the bwlch we could see Ray and
his son beside a large sheep pen, we stopped and chatted, they were just about
to separate their sheep from any lingering souls who had joined from
neighbouring herds and treat them against scab.
Heading down from the hill |
As the sun sank behind a
hill ridge to our west the last half hour back to the awaiting car proved a
slightly chilly affair with autumnal clear skies heralding the onset of another
cold winter.
Survey Result:
Colfa Hill
Summit Height: 532.2m (converted to OSGM15, Trimble GeoXH 6000)
532.2m (converted to OSGM15, Leica GS15)
532.2m (converted to OSGM15, Leica GS15)
Summit Grid Reference: SO 19449 55397
Bwlch Height: 387.8m (converted to OSGM15, Trimble GeoXH 6000)
387.7m (converted to OSGM15, Leica GS15)
387.7m (converted to OSGM15, Leica GS15)
Bwlch Grid Reference: SO 17968 55359
Drop: 144.4m (Trimble GeoXH 6000) 144.6m (Leica GS15) (Submarilyn
status confirmed)
Dominance: 27.16% (Leica GS15)
status confirmed)
Dominance: 27.16% (Leica GS15)
For further details please
consult the Trimble survey spreadsheet click {here}
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