Saturday, 28 April 2018

Mapping Mountains – Trimble Surveys – Tarennydd

01.04.18  Graig Goch (SH 714 084), Tarren Cadian (SH 729 072), Tap Llwyd (SH 719 065), Tarren y Gesail (SH 710 058) and Graig Wen (SH 694 068)

Graig Goch (SH 714 084)

The hills of the Tarennydd are like forgotten beasts nestled as they do against their higher and more dramatic neighbour of Cadair Idris.  Their slopes and ridges have been ravaged by man, with many now swamped in regimented conifer plantations and higher cymoedd dug deep with old mine workings.  However, they do have a peaceful charm, one where few people tread.

The circuit of Glyn Iago was suggested by Aled, who I met in Abergynolwyn at 8.30am on Easter Sunday, with the previous day damp and grey and the next forecast for heavy, persistent rain, we had chosen wisely as an early morning chill pervaded the land with edges of blue sky and a forecast of dry overhead conditions.

Having left one car in Abergynolwyn we drove toward the farm of Rugog and left the other in a large lay-by on the A 487.  This enabled an ascent of Graig Goch via its north-eastern slopes on a gauged out track that meanders its way up the hill from the aforementioned farm.  On our way we called at the farm to make place-name enquiries and were met by a number of barking dogs and one of the two occupants appearing in her dressing gown, after a cordial chat and permission to use the track we set off uphill.

As height was gained the bulk of Cadair Idris with its snow-capped slopes bulged in to view, a dramatic scene dominating the western view, ahead lay the upper reaches of Cwm Dylluan and the large conifer plantation that takes in much of the lower slopes of these hills, however much of the upper section of trees had been felled which would help in connecting Graig Goch with Tarren y Gesail and hopefully with a number of surveys that were planned for the day ahead.

Cadair Idris

The felled forestry leading from Graig Goch to Tarren Cadian

The track petered out near the summit of Graig Goch with a narrow path leading toward the hill’s high point, as I set the Trimble up Aled headed off to investigate the western slopes which plunged down in a dizzying way to the watered calm of Tal y Llyn below.

Gathering data at the summit of Graig Goch

Dizzying views down to Tal y Llyn

Cadair Idris and Tal y Llyn

Leaving the summit we back-tracked toward the end of the track before venturing in to the felled forestry which quickly brought us down to the connecting bwlch which consisted of a T-junction forest track, and once five minutes of data were collected with the Trimble we headed up a zig-zagging bulldozed narrowing track that led up toward the connecting north-easterly ridge of Tarren y Gesail where two hills were positioned that were going to be Trimbled.

At the bwlch of Graig Goch

The felled forestry beyond the end of the narrow bulldozed track

The going on the ridge consisted of moorland tussocks with a slight path of sorts leading beside the ridge fence toward the high point of Tarren Cadian, a 597m map heighted hill whose summit peered out on more conifer plantation to the south-east.

On the ridge leading to Tarren Cadian

Aled heading for the summit of Tarren Cadian

Two tussocked hummocks vied for the high point of the hill, we used an improvised method of levelling to determine the higher and once the Trimble had gathered its allotted data we set off on the continuation of the ridge down toward the connecting bwlch which we judged to be positioned amongst the conifers, this was Trimbled before we excavated ourselves from the trees and headed up toward Tap Llwyd.

Gathering data at the summit of Tarren Cadian

Not the best place for a survey

This next hill is given 15m of drop on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, and with a summit over 500m in height, it should, according to these figures qualify for Uchaf status.  However, I surveyed this hill in September 2005 as having 44ft 6˝ / 13.6m of drop, on that day I could only survey the high point of the hill that remained out of the conifer plantation and with no knowledge of the spot heights that would later appear on the Geograph map I was satisfied that this hill was not an Uchaf.  But today we found the forestry felled which gave the opportunity to survey two points for the summit and two for the bwlch position.

Gathering data at the high point outside of the felled forestry

The first potential summit point to be surveyed was beside the ridge fence, the second was amongst the debris of felled trees, on ground laid waste by the blight of conifers.  These were followed by the bwlch with two points surveyed to ground at the base of the ridge fence.  Happy with our efforts we plodded on.

Following the ridge fence toward the high point in the felled forestry with Tarren y Gesail in the bcakground

Gathering data at the summit of Tap Llwyd

Gathering data at one of two positions surveyed for the bwlch position of Tap Llwyd

The next part of the walk consisted of putting your head down and plodding uphill and in the process gaining about 110m of height toward the connecting fence to the trig pillar atop Tarren y Gesail.  As Aled munched on a sandwich beside the small wind shelter next to the trig I set the Trimble to gather data amongst a sea of tussocks, any of which could have laid claim to being the summit.  Aled then investigated the high land of tussocks and suggested a second data set was taken nearer the trig, once this was done we headed down toward a forest break that led to a forest track which headed toward our last hill of the day; Graig Wen.

Looking back toward Tap Llwyd and Tarren Cadian

Pick your tussock - gathering data at the summit of Tarren y Gesail

The forest track conveniently passed over this hill’s connecting bwlch which was Trimbled and then followed a slow plod uphill leading to the summit of Graig Wen.

Gathering data at the critical bwlch of Graig Wen

By now the wind had increased in strength and the cloud had caused a milky sun which heralded the incoming weather front that would soak the land the following day, thankfully we remained dry for the nine hours that we were on the hill.

The summit of Graig Wen consists of an attractive rocky knoll and as the Trimble gathered data I sat with Aled trying to shelter from the chilled wind.  Once data were stored and the Trimbke closed down and packed away we headed down toward the high dead end paved road leading to the old Bryn Eglwys Quarry.

Gathering data at the summit of Graig Wen

The paved road is steep in places but gave a relatively quick descent to the awaiting car parked in Abergynolwyn.  It had been another good day on the hill with five hills surveyed and a new Pedwar in Graig Wen bagged, and with new land covered connecting Graig Wen with Tarren y Gesail.


Survey Result:

Graig Goch

Summit Height:  585.6m (converted to OSGM15)

Summit Grid Reference:  SH 71479 08459

Bwlch Height:  455.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 72601 08269

Drop:  129.7m

Dominance:  22.14%

Tarren Cadian

Summit Height:  598.1m (converted to OSGM15)

Summit Grid Reference:  SH 72947 07296

Bwlch Height:  529.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 72369 06752

Drop:  68.7m

Dominance:  11.48%

Tap Llwyd

Summit Height:  565.7m (converted to OSGM15)

Summit Grid Reference:  SH 71990 06571

Bwlch Height:  550.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 71857 06414

Dominance:  2.70%

Remoteness:  2.875km (Pellennig addition confirmed)

Tarren y Gesail

Summit Height:  666.5m (converted to OSGM15)

Summit Grid Reference:  SH 71031 05890

Bwlch Height:  201.2m (LIDAR)

Bwlch Grid Reference:  SH 73733 09375 (LIDAR)

Drop:  465.3m (Trimble summit and LIDAR bwlch)

Dominance:  69.81%

Summit Height:  454.1m (converted to OSGM15)

Summit Grid Reference:  SH 69405 06806

Bwlch Height:  367.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 69874 06631

Drop:  86.7m

Dominance:  19.08%

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