Monday, 14 May 2018

Mapping Mountains – Trimble Surveys – Moel Hebog



08.04.18  Pt. 532.7m (SH 574 441), Moel Ddu (SH 579 441), Moel Ddu (SH 579 442) and Mynydd Gorllwyn (SH 585 427)

Moel Ddu (SH 579 442)

Today’s walk proved a good circuit of hills above Llyn Cwmystradllyn in the company of Mark and Aled, with the main surveying objective being a 534m map heighted hill that I had surveyed in May 2000 using a basic levelling technique as having 29.1m of drop.  This we planned on combining with the two higher Moel Ddu summits and the 239m map heighted Mynydd Gorllwyn as our last hill.

The early morning low cloud had risen by the time we set off walking around the western side of the lake, following an old track past forgotten and derelict farmsteads whose robust lower walls still stand firm.

Mark and Aled on the track leading to the Gorseddau Quarry

Although the forecast was good there was still a winter feel to the land with bare trees and fawn coloured reed grass enclosing the adjacent fields.  Passing the old Plas-llyn and its shielding copse of trees, moss predominated on the lower bark and root, a sign of damp and the passage of time.

Moss on trees

Ahead lay the remains of the Gorseddau Quarry with the lofty heights of Bryn Bannog above, one merging in to the other.  We stopped for a bite to eat close to a quarry wall that would not be out of place in the stone work of the Inca.  Here I de-layered as sun broke through high cloud and the warmth of spring gave a welcoming feel.

Bryn Bannog and the Gorseddau Quarry


This wall wouldn't be out of place in Cusco


Moel Hebog

The first point to survey was a short distance above and consisted of a large, flat looking bog, this is the bwlch of Moel Ddu, and I sloshed about in its unsavoury depths for a few minutes trying to find where the most appropriate placement was for its critical point, during this Aled and Mark stood on a raised hummock of dry land directing me one way and the other, I eventually opted for land close to the stone wall that crosses the bwlch.

Gathering data at the critical bwlch of Moel Ddu

The upper part of Moel Ddu now dominated the horizon, this is a fine hill set back from its higher neighbours and we had about 200m to gain in height before standing on its summit, and most of this uphill proved rather steep.

Moel Hebog and the Gorseddau Quarry


The ascent toward the Moel Ddu ridge

Nearing the ridge connecting to Moel Ddu we had options for which summit to visit first and decided to head for the hill that I had surveyed 18 years ago.  This hill has two tops vying for its high point, and both were Trimbled.  During this the waters of Llyn Cwmystradllyn nestled in the high valley below and reflected sky and cloud.

Gathering data at the first of two surveys for the summit position of Pt. 532.7m


Llyn Cwmystradllyn

The second top surveyed for summit position has a large flat rock on its high point and the merit of including this in the measurement of the hill was debated at length as when standing on it, it wobbles.

Gathering data at the second of two surveys for the summit position of Pt. 532.7m

The next surveying objective was the connecting bwlch of this hill and as Mark and Aled soaked in the sunshine and view, I headed down toward the bwlch and used the ten figure grid reference produced by LIDAR analysis for positioning of the Trimble atop my rucksack, and once the measurement offset was taken between its internal antenna and the ground below, I waited for the 0.1m accuracy level before data should be gathered and then pressed ‘Log’ and waited for the allotted data points to be collected and stored.  Next stop the summit of the southern top of Moel Ddu.

Gathering data at the critical bwlch of Pt. 532.7m

This hill had also been surveyed using a basic levelling technique in May 2005 and today with Aled’s assistance the Trimble was positioned rather precariously on a balanced rock on the edge of the summit cairn, with an offset taken to the highest part we could find of the large rock that sits below the cairn.

The two Moel Ddu summits

As the Trimble beeped away gathering another data set Mark and then Aled headed over to the higher summit of Moel Ddu, and once the Trimble had done its stuff I joined them.

Gathering data at the summit of Moel Ddu (SH 57911 44136)

By now threatening dark grey cloud was massing to the east with the peaks of the Arenig immersed in what was no doubt heavy rain, thankfully we were still in sunshine but we wondered if the rain would edge our way.

The Trimble was positioned a few metres from the base of the large cairn atop the higher of the Moel Ddu summits on ground that the three of us judged was higher than that at the immediate base of the cairn.  As data were gathered the dark grey cloud began its slow path westward toward the high Moelwynion which were now bathed in threatening grey.

Gathering data at the summit of Moel Ddu (SH 57958 44205)

To our north the hills of Yr Wyddfa were also bathed in the mass of grey cloud as indeed was Cnicht, with light and shade giving depth to the land, and yet we remained in sunshine.

Dark clouds massing

Cnicht

Before leaving the confines of Moel Ddu I wanted to survey the connecting bwlch between the two summits, this was on moor grass away from the high stone wall that passes over the bwlch and also away from the steepening slopes of the lower summit.

Gathering data at the critical bwlch of the lower of the two Moel Ddu summits

We had one hill remaining to visit; Mynydd Gorllwyn which was southward from where we now were and entailed loosing height down toward land to the north of its bwlch.  The bwlch looked another boggy affair and its survey could wait until after the summit.

Mynydd Gorllwyn

Mynydd Gorllwyn is a fine hill, sunbathed as it was when we visited with rain showers to its south across the northern Rhinogydd, it dazzled in the sun invitingly and we headed toward its north-western slopes on a semblance of green land away from the fawned land of tussocks that pre-dominated the hill.

Cnicht

Cnicht and Moelwyn Mawr

Storm clouds massing over the Moelwynion

The going to the summit proved tough at the end of a long day on the hill with heat and steep ground proving wearisome, but soon the high point came in to view and as we sat and soaked in the land to our south that plunged down to the valley below, the Trimble beeped away gathering its last summit data set of the day.

Striking light on Moel Ddu

Gathering data at the summit of Mynydd Gorllwyn

All that remained was the connecting bwlch and this was in a land infested with high tussock grass that few must venture to.  As I remained with the Trimble, Aled and then Mark headed up to a track that would in time lead us back to my car.  However, I waited at the bwlch resting beside a fence until the last of the day’s data sets was stored and then slowly sweated my way up to the track to join them.

Nearing the end of another excellent day

The track headed southward as the grey mass of rain cloud edged northward away from us.  Arriving back at the car and getting my boots off was a delight, we were soon sitting in The Ring at Llanfrothen enjoying an evening meal and good conversation, a perfect way to end the day.

  

Survey Result:


Pt. 532.7m

Summit Height:  532.7m (converted to OSGM15)

Summit Grid Reference:  SH 57455 44182

Bwlch Height:  503.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 57647 44157

Drop:  28.9m (500m Sub-Twmpau status confirmed)

Dominance:  5.42%




Moel Ddu

Summit Height:  550.1m (converted to OSGM15)

Summit Grid Reference:  SH 57911 44136

Bwlch Height:  535.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 57942 44164

Drop:  14.5m (500m Sub-Uchaf status confirmed)

Dominance:  2.64%




Moel Ddu

Summit Height:  552.4m (converted to OSGM15)

Summit Grid Reference:  SH 57958 44205

Bwlch Height:  353.0m (converted to OSGM15)

Bwlch Grid Reference:  SH 57581 44928

Drop:  199.5m

Dominance:  36.11%




Mynydd Gorllwyn

Summit Height:  239.3m (converted to OSGM15)

Summit Grid Reference:  SH 58519 42702

Bwlch Height:  197.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 58095 42705

Drop:  41.4m

Dominance:  17.30%






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