05.04.25 Lan Ddu Fawr (SN 787 699) and Carn yr Hyrddod (SN 790 704)
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| Lan Ddu Fawr (SN 787 699) from the summit of Carn yr Hyrddod (SN 790 704) |
Due to independent
surveying and LIDAR analysis there are few important hill surveys that remain. Lan Ddu Fawr and Carn yr Hyrddod are two of
these hills. They are placed in the open
grasslands of the Elenydd, approximately 0.5km apart. Both are topped by the remains of ancient
cairns, with scattered rock at their summits.
Considering the wild
surrounds of each hill, they are relatively easy to access, with the minor road
leading toward the Llynnau Teifi to their south. The paved section of this road turns to track
and continues to Claerwen; one of the remotest farms in Wales. The track continues from this farm around the
northern section of the Claerwen Reservoir, before turning back to a paved road
and its continuation east toward Rhayader Gwy.
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| The Llynnau Teifi |
Lan Ddu Fawr is given a
593m spot height on contemporary Ordnance Survey maps with a triangulation
pillar perched in the remains of the ancient cairn which is now fashioned as a
wind shelter. With the flush bracket adjoined to the trig pillar recorded as 592.836m in height. Whilst, Carn yr Hyrddod is given a 594m summit
spot height, which is coloured beige on contemporary Ordnance Survey maps, this
indicates an air height, the accuracy of which is not as good compared to that
of the flush bracket height.
As current maps give
Carn yr Hyrddod 1m higher, it is this hill that is prioritised for listing
purposes. Its classification can be
viewed as important as it is listed as a Marilyn, Dewey, Dodd, a Welsh Highland
P15 and a 500m Twmpau. Confusingly the
hill originally appeared in the Marilyn and Dewey listings as Waun Claerddu,
which applies to land incorporating a large bog to the south-east of the summit
of Lan Ddu Fawr. To add confusion upon
confusion the Marilyn list has recently changed its listed name to Lan Ddu
Fawr, which applies to the lower map heighted hill and not the higher.
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| Extract from the Ordnance Survey 1:25,000 Explorer map |
These hills had been on
our surveying radar for over a year as the higher map heighted hill is one of
our named hills for our Groups within our Regions and Sub Regions. Whilst, the lower hill is also close to Welsh
Highland P15 status with LIDAR giving it 14.6m of drop. Therefore, our plan was to survey each
summit, gathering at least two - three data sets from different positions and
also to survey the connecting bwlch between the hills. The weather forecast for the day’s adventure
gave clear blue skies, albeit with a brisk chilling easterly wind.
I met Aled at Dinas
Mawddwy at 7.30am and proceeded to drive toward Aberystwyth and then the roads
heading south before connecting with the narrow road leading to Llynnau
Teifi. We parked close to a cattle grid
and fence that headed up toward our hills.
As I opened the car door, the wind hit me and I quickly changed from
shorts to walking trousers. Thankfully
Aled had brought spare gloves which I needed as I had dispensed with my winter
gear in favour of a thin pair that would only protect from a slight chill, and
that easterly wind definitely needed extra protection as it was chilling to the
bone.
From where we parked
there are two options for a relatively easy route toward the first of our hills;
Lan Ddu Fawr. One is a wide shaly track
rising steeply above the road; the other is a comfortably gradiented green
vehicle track that headed up beyond the cattle grid and would in time follow
the course of a fence. I was in
following Aled mode and he soon headed up the steep shaly section. Beyond was open hillside and miles of it in
every direction. This is one of the
appeals of the Elenydd and few places in Wales can compare.
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| Heading to the hill |
Our route soon joined
the remains of a leet that contoured around grassed hummocks to our west. Aled soon left me to bag a P10 sub. He had a number of these on his planned
route, which would leave me on the summit of Carn yr Hyrddod and take a circuitous
route across the grass and bog toward Bryn Dafydd, before heading back to
Trawsallt and continuing to Disgwylfa and eventually more sub hills before
reaching the relative comfort of the paved road below. This would leave me to survey the summits of
Carn yr Hyrddod and Lan Ddu Fawr, via the connecting bwlch, surveying all
necessary points on the way, before heading back on our inward route to meet
Aled back at the car.
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| Lan Ddu Fawr above Waun Claerddu |
Aled soon bagged the P10
sub and rejoined me as the leet headed toward a forlorn looking gate. Here we rested whilst I set the Trimble up on
a gate post to attune it with satellite configuration. From here we contoured around the upper part
of Waun Claerddu before heading up the steep southerly slopes of Lan Ddu Fawr,
which took us to its summit. By now we
were exposed to the wind and it whisked across the hill, so much so that unless
hunkered down behind the wind shelter it proved difficult to communicate. We spent ten minutes or so assessing the
summit area and judging what points needed to be surveyed. Having picked three candidates we headed off
following a sheep track on the moor down toward the connecting bwlch.
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| Leaving the summit of Lan Ddu Fawr and heading toward Carn yr Hyrddod |
If not for the ten
figure grid reference produced by LIDAR it would be difficult to pinpoint where
the critical point of this bwlch lay, as it consists of much bog, which today
was thankfully almost bone dry. Writing
this post on the 6th April follows the driest month of March ever
recorded in Wales and England, and the first few days of April have been the
same. This helped us during the walk as
few places were boggy and that included the bwlch we were now walking
through. Remembering the LIDAR lay-out
of this bwlch, Aled pointed toward its critical point as we headed through its
stunningly wild surrounds toward the steepening slopes of Carn yr Hyrddod.
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| The bwlch between the two hills |
As we crested the upper
ridge the wind hit us again. At least
the confines of the bwlch had given some respite from its chilled extremes. This summit consists of a relatively modern cairn
and beside it the jumbled remains of the ancient cairn. We again assessed the lay of land and
pinpointed three positions to survey. At
each summit we looked for large rocks that could be deemed as being part of the
natural hill. There is plenty of rock at
each summit, but none that could be described as large enough to be a part of
the natural hill and therefore surveys were taken to either grass or the ground
at the base of the rock.
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| Aled at the summit of Carn yr Hyrddod |
As we made our way to
the summit a figure appeared beside the wind shelter on Lan Ddu Fawr, by the
time our summit assessment was complete he had joined us. Kevin Nicholls had driven up from Cardiff and
was part of the SOTA – Summits on the air community, and planned on setting up
his gear back on the summit of Lan Ddu Fawr.
He then headed back toward this summit, and soon afterward Aled was off
on his wild hill bagging trek. I watched
as he headed down toward a near bog before claiming height on a ridge leading toward
the summit of Bryn Dafydd.
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| Aled heads off in to the wilds of the Elenydd |
This left me to my
surveying activities. I knew what needed
to be done and even though the wind was proving fierce I had faced similar
conditions on a few hills before.
However, with six planned surveys on the two summits I knew that the
wind would hinder me more so than the Trimble, as even writing the notes in my
surveying notebook proved cumbersome and especially so when the wind was blowing
my camera strap and Trimble bag back over my head!
I soon found a suitable rock to place above the first point to survey and positioned the Trimble on top of it, wedging it in place with two smaller rocks. This proved an ideal solution to the wind and would be employed on the remaining summit surveys. Having taken a measurement offset from the equipment’s internal antenna to the ground at its base, I waited patiently for the 0.1m accuracy level to be attained before data should be logged, and once achieved I activated it to gather data.
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| Gathering data at the summit of Carn yr Hyrddod |
During data collection I
stood a safe distance away from the equipment so as not to hinder satellite
reception, scribbled all necessary detail in my survey notebook, whose pages
were flapping about in the wind. Once
five minutes of data were collected and stored I turned the equipment off, took
a series of photographs and repeated the process at two further points. Progress was being made.
Leaving the summit of
Carn yr Hyrddod I headed back down to the sheltered confines of the connecting
bwlch. Using the Trimble as a hand-held
device I zeroed in to the ten figure grid reference produced by LIDAR
analysis. The DTM and DSM model give the
critical bwlch approximately 5 metres apart.
I favoured using the DTM model as the critical point, and this led me to
a small channel amongst copious amounts of rather beautifully coloured grass tussocks.
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| Gathering data at the connecting bwlch between the two hills |
Wanting a rest from the buffeting wind I decided to take two data sets, both from the same position,
with the Trimble placed on top of my rucksack, with its base firmly wedged in
the bottom of the channel. After the
first data set was complete I re-positioned the rucksack over the same point but
with the Trimble now facing a different direction and set it to gather another
five minute data set, during which I sat and looked at some extraordinary
purple coloured bog enjoying lichen encrusted bulbous beauty that covered the
edge of a near peat hag. This and
looking up toward the summit of Carn yr Hyrddod occupied the next few
minutes. Sometimes surveying can take
you to some out of the way places, that in their own right are extraordinarily
peaceful and have a tranquility all their own, and this connecting bwlch was
one of those places.
Once the second bwlch
survey was complete I packed the equipment away and headed around any bog and joined
the ridge leading to the summit of Lan Ddu Fawr. Nearing the top I looked east toward the
ridge connecting with Trawsallt and spotted a small figure heading toward its
summit. It was Aled. He had made good progress and I thought that
he’d probably get back to the car before me as I still had three data sets to
gather atop Lan Ddu Fawr.
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| Aled on his way to Trawsallt |
When I arrived back at
the wind shelter Kevin Nicholls was hunkered down with his aerials already set
up and transmitting, talking to friends in various parts of the country. I said hi and explained that I wanted to take
a series of data sets and would be doing so on the far side of the wind shelter
for around 25 minutes. He indicated that
he would remain where he was whilst I did my stuff.
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| Kevin Nicholls hunkered own with his SOTA equipment in place |
I soon had the first position
set up, again using a rock to place the Trimble on and two others to wedge it
in place. Once the measurement offset
was taken I retreated as it collected another data set. Once complete I headed back around the cairn
to tell Kevin that the first was now complete and two more were to be taken.
This routine of using a
rock to slightly elevate the Trimble and give it a solid platform and to
protect it from any wind disturbance with two wedged rocks, proved ideal and
soon the second data set was complete.
Before moving the Trimble to the last position I again headed off to
tell Kevin that only one remained to take.
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| Carn yr Hyrddod from Lan Ddu Fawr |
The third position was
going to be the most difficult to get a good data set from as Aled and I had
decided that one needed to be taken at the entrance to the wind shelter. This meant that even with its slight
elevation on its rock the Trimble was faced with higher rock immediately above
on three sides. This is not conducive to
either attaining the 0.1m accuracy level before data should be logged, let
alone attaining a good data set, we will have to wait and see what the
processed data gives.
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| Gathering data at the summit of Lan Ddu Fawr |
As the last data set was
nearing completion Kevin was packing up his gear and therefore a quick bit of
wind driven conversation later and we decided to head down the hill
together. All that remained was to take
a few photos of the last of the eight survey positions taken during the day,
pack the equipment away, get my rucksack on and join Kevin as we headed down
the hill.
Our route took us back
to the gate where on the ascent I had taken a data set to attune the Trimble to
the local satellite reception. From here
we opted to follow Kevin’s inward route, walking on a good quad bike track beside
the fence line. We took our time on our
outward walk with lots of good conversation.
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| Kevin Nicholls |
By the time we arrived
back at the two awaiting cars, Aled was already there, flat on his back resting
in the sun. He’d made good time on his
route around the hills. Before leaving
we chatted with Kevin for quite sometime about the various hills he’d transmitted from and those he hoped to visit.
It had been an excellent day on the hill, with all plans fulfilled. It should be an interesting survey result!
Postscript:
The processed Trimble result could not split the heghts of these hills and therefore they are now listed as a twin top in the Deweys and 500m Twmpau lists. However, for convenience the data given below uses Carn yr Hyrddod as the prioritised hill. Please click here for more information relating to the Dewey twin top announcement.
Survey Result:
Lan Ddu Fawr (significant name
change for the Deweys)
Summit Height: 592.7m (converted to OSGM15) (summit relocation based on twin top for the Deweys) (summit relocation based on twin
top for the 500m Twmpau)
Summit Grid Reference: SN 78759 69974
Bwlch Height: 578.1m (converted to OSGM15, average of two
surveys)
Bwlch Grid Reference: SN 78931 70288
Drop: 14.6m
Dominance: 2.47%
Carn yr Hyrddod (significant
name change for the Deweys)
Summit Height: 592.7m (converted to OSGM15, Trimble GeoXH
6000) (summit relocation based on twin top for the Deweys) (summit relocation
based on twin top for the 500m Twmpau)
Summit Grid Reference: SN 79069 70421 (Trimble GeoXH 6000)
Bwlch Height: 424.8m (LIDAR)
Bwlch Grid Reference: SN 79547 66955 (LIDAR)
Drop: 168.0m (Trimble GeoXH 6000 summit and LIDAR
bwlch)
Dominance: 28.34% (Trimble GeoXH 6000 summit and LIDAR
bwlch)
For further details please consult the Trimble Survey Spreadsheet
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