Mapping Mountains – Trimble Surveys – Mynydd Epynt

30.12.19  Noethgrug (SN 837 373, not Trimbled) and Mynydd Bwlch y Groes (SN 868 356)  

Mynydd Bwlch y Groes (SN 868 356)

Visiting the hills of Mynydd Epynt between Christmas and New Year is becoming an annual tradition.  The land comprising the majority of this hill range is sadly out of bounds for much of the year due to military occupation.  However, all people deserve a holiday, and whilst the military are away this land becomes a quiet place, with just an occasional farmer spreading feed for grazing sheep and a rogue hillwalker or two.

Today we planned on visiting two Pedwar hills; Noethgrug and Mynydd Bwlch y Groes, with two 300m P30s as optional extras.  We were walking by 10.00am starting from the upper reaches of the Nant Gwennol valley where a forest track gained height up in to the misted realm of the conifer plantation.

The Nant Gwennol valley

Mist and conifers are well suited, neither are my favourites, but when combined they give an isolated solitude where darkened shapes of regimented trees merge.  Having gained height we left the main forest track and headed toward the summit on a narrow track which soon deposited us back on to the main forest track.

Leaving the main forest track

It was now time for a bite to eat as the next part of the walk involved tree bashing and following a ten figure grid reference toward the high point of Noethgrug with the aid of a hand-held GPS.

The outer trees gave some form of protection toward the inner, with the latter dark and dead with little greenery.  Patches of greenery only emerged the higher we got, with the summit beside an odd patch of green squeezed in amongst a mass of conifered branches.

The Trimble was set up beside the summit half way up a tree with the measurement offset noted between its internal antenna and the ground below.  There wasn’t much hope of it ever achieving the 0.1m accuracy level before data should be logged and after a few minutes I switched it off, packed it away and followed my two companions further in to the forest as we tried to find an old path back to the main forest track.

At the summit of Noethgrug

The old path was found, it had not been maintained and the trees soon enveloped us again.  Nearing the main forest track we came upon a few trees encrusted in moss.  Standing with branches sprayed out and greened with winter light adding to the background mist.  I stood and looked, a moment to savour before the next few miles on the continuation of the forest track.

Moss encrusted trees

We stopped where a narrower path led toward the summit of the first of the two optional 300m P30s.  We knew by now that time did not permit a visit as there was still a few miles to go to the top of our last hill; Mynydd Bwlch y Groes.

On the forest track to the north of Noethgrug

The forest track took us on to a paved road with the Epynt red flag flapping in the slight breeze, I took a few photos and we then continued.  A series of paved roads now took us over a slight ridge and up toward the public road that speeds its way beside the summit of Mynydd Bwlch y Groes.

One of the landmarks of the Epynt

Greeting us at the junction where the public road heads southward were signs for Dixie’s Corner; an unusual name so close to a Welsh summit.  The Epynt can be a surreal place to visit, with much of it out of bounds, but tranquillity can still be found, although the occasional passing vehicle as we marched up the road toward the triangulation pillar atop Mynydd Bwlch y Groes broke the silence and added to the surreal element as they quickly approached and disappeared again in to the mist.

An unusual name to find near the summit of a Welsh hill

Reaching the summit was welcome and gave me the opportunity to at least survey one summit or bwlch for my endeavours.  The Trimble was soon set up atop my rucksack gathering its allotted data.  During data collection I stood with my two companions and chatted and only stopped doing so after 11 minutes of data were gathered and stored.

Gathering data beside the trig pillar of Mynydd Bwlch y Groes

We left the summit and retraced our way back toward Dixie’s Corner and its near large barns and then headed westward down a wide track which shot downward in a military style straight line.  At its bottom there was now height to regain, again on the track, this was unwelcome at the end of the walk, but it had to be done.

Down from the hill

The track led us to an enclosed lane, passing a large old house on the way.  The old lane forever lost height fording the stream at its bottom before the last bit of torturous uphill back to the awaiting car.

LIDAR summit image of Mynydd Bwlch y Groes

LIDAR bwlch image of Mynydd Bwlch y Groes

LIDAR – Postscript

Since visiting 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 Mynydd Bwlch y Groes have been analysed using this technique, resulting in LIDAR being prioritied in favour of the Trimble GeoXH 6000 summit result.

Survey Result:

Noethgrug 

Summit Height:  412m (spot height)

Summit Grid Reference:  SN 83711 37384 (hand-held GPS via DoBIH)

Bwlch Height:  c 293m (interpolation)

Bwlch Grid Reference:  SN 84875 39048 (interpolation)

Drop:  c 119m (spot height summit and interpolated bwlch)

Dominance:  28.88% (Trimble summit and interpolated bwlch)

Mynydd Bwlch y Groes

Summit Height:  441.9m (LIDAR)

Summit Grid Reference:  SN 86898 35691 (LIDAR) (summit relocation)

Bwlch Height:  305.05m (LIDAR)

Bwlch Grid Reference:  SN 88817 38632 (LIDAR)

Drop:  136.9m (LIDAR) (Submarilyn deletion)

Dominance:  30.97% (LIDAR)

For further details please consult the Trimble Survey Spreadsheet