Mapping Mountains – Trimble Surveys – Arenig

01.07.17  Pen y Foel Ddu (SH 753 394), Foel Cynfal (SH 749 395), Pt. 548.6m (SH 743 393), Graig Wen (SH 739 394), Moel y Croesau (SH 748 383) and Pt. 369.5m (SH 739 374)

Pt. 548.6m (SH 743 393) with Arenig Fawr in the background

I’ve often looked over to my left when travelling the minor road beyond Llyn Celyn that skirts the wilds of the Y Migneint and heads toward Llan Ffestioniog, and often thought that an approach to the hills taking in Graig Wen looked a boggy and pathless affair, and therefore always shied away from making an ascent from this side, however this was the ascent route suggested by Aled and with a second car left at the entrance to Bryn-celynog it would give an opportunity to visit and Trimble a number of hills, including two marginal Uchaf hills, one of which had been on Aled’s radar for a number of months.

A green track confidently leaves the minor road and looks as if it’s heading straight up toward the hills, unfortunately it abruptly ends with a narrow path continuing next to the course of a fence line, this also soon peters out with only the remnants of sheep paths to follow.

Heading toward the first hill of the day

The fence line led us to ground beside the quietly situated Llyn Cors-y-barcud, which today was a tranquil spot nestled and forgotten amongst its reed grass and bog.  A grassed ridge of sorts headed up and I slowly followed Aled toward the first summit of the day.

Llyn Cors-y-barcud

Aled heading toward Pen y Foel Ddu

Pen y Foel Ddu is the last hill of any subsequent prominence on the eastern side of this compact group, I’d visited this hill in September 2005 when immersed in my basic levelling surveys (BLS) with the resulting drop value being 50ft 6˝ (15.4m).  There is an overgrown cairn at the summit and I quickly set the Trimble up on my rucksack which was positioned on its back as there was a brisk breeze blowing, measured the offset between its internal antenna and the ground below and joined Aled away from the equipment for its five minutes of allotted data collection.

Gathering data at the summit of Pen y Foel Ddu

The next three hills and their respective bylchau and summits came quickly and at each we assessed the lay of land and gathered another five minute data set.  After surveying the summit of Pen y Foel Ddu the next point to gather data from was its bwlch, this consists of a browned water laden bog, and data were gathered from the northern and southern extremities of its watery ground.  Whilst assessing these points a grouse shot up from immediately beside us, a busied flap of wings and off it went, I’ve experienced this on the hill many times over the years, but then three young grouse shot up in all directions, quickly followed by two others and finally a single youngster shot up and away, they flew off in all directions with some of the youngsters following each other and others just skimming the moor grass and coming to rest beyond our eyesight.  This all happened so quickly and straight at our feet, the mother later had the attentions of a hawk which flapped down for the kill, it again shot off heading this time toward Aled and rested in the grass close by using it and also probably us for cover.

Gathering data at one of two points surveyed for the critical bwlch position of Pen y Foel Ddu

Pen y Foel Ddu and its water laden bwlch from the ascent of Foel Cynfal

Heading west the next summit belonged to Foel Cynfal, a relatively flat topped hill without a spot height on any map that I’ve seen.  Once at its summit the ground was assessed and the point judged the highest chosen, and the Trimble set up to gather data.  As I waited beside Aled for the 300 datum points to be stored, the morning’s blue sky had changed slightly with bulbous clouds occasionally blocking the warmth and colour given by the sun, and with a forecast of rain sweeping in from the west at approximately 4.00pm – 5.oopm we knew we could not linger if we were to get back to the awaiting car, dry.

Gathering data at the summit of Foel Cynfal

The next bwlch was positioned to the west and the steep grassed slopes leading down to it helped in assessing its critical point, I headed to its northern extremity and as this looked like the boggied outflow we concentrated our assessment on its southern side, and again the Trimble was set up and gathered its allotted five minutes of data.

Gathering data at the critical bwlch of Foel Cynfal

Our next hill lay on the land heading toward Graig Wen and it was a hill that I’d surveyed with my old wooden staff in September 2005, resulting in its inclusion in the fledgling Uchaf list, I remembered that it has two tops and these were on display as we followed sheep paths and contoured up on ground toward it.  We judged the first top which is the more northerly as the higher.  I set the Trimble up on my rucksack which was laid on its back as the breeze whipped across the hill.  This summit is a fine one and it would be sad to see it go from the Uchaf list if proven to have less that 15m of drop, before heading down to its connecting bwlch we walked to the southern top and peered back and agreed that this was lower.

The land leading toward the two tops of Pt. 548.6m (SH 743 393)

Looking back toward Foel Cynfal

Gathering data at the summit of Pt.548.6m (SH 743 393)

The connecting bwlch proved more expansive than those previously encountered but assessing the lay of land from a number of directions and vantage points helped in judging the placement for the Trimble.  Once five minutes of data were stored the equipment was packed away and we headed up toward the cairned summit of Graig Wen.

Gathering data at the critical bwlch of Pt. 548.6m (SH 743 393)

Pt. 548.6m (SH 743 393)

Pt. 548.6m (SH 743 393) with Arenig Fach in the background on the right

I positioned the Trimble on the highest rock of the cairn having moved one or two to accommodate proper placement, then measured the offset to the highest ground at its base and sat with Aled waiting for five minutes of data to be collected.  By now a ribbon of grey cloud was emerging way off on the western horizon heralding the forecast rain, so once the Trimble was packed away I followed Aled back along the broad eastern ridge and down to a land of bog and wilderness.

Gathering data at the summit of Graig Wen

We aimed for a dry hummock close to where pylons crossed this land, this according to LIDAR data that Aled had analysed is where the critical bwlch of our next hill; Moel y Croesau, lay.  I felt knackered when we arrived but the ten figure grid reference obtained from Aled’s analyses soon led me to the correct Trimble placement and again the customary five minutes of data were gathered.

Gathering data at the critical bwlch of Moel y Croesau

The following ascent to the summit of Moel y Croesau seemed to go very quickly, and once there we used the LIDAR placement to zero in on one of two high points.  I soon assembled the Trimble on top of my rucksack which was again positioned on its back.  Our route down was via a gravelled track that heads through these hills that once must have given access to the small mines dotted beside the Afon Llafar. 

Emperor moth caterpillar

Gathering data at the summit of Moel y Croesau

Llyn y Garn with Moel Llyfnant in the background

The gravelled track led down to the remains of the old farm house of Dolddinas and the blue skies of earlier had now been replaced with white cloud as the westerly rain front edged ever nearer.  The track now turned in to a greened path that led up toward Llyn Hiraethlyn, as the high point of this greened path was only just below a Trichant we headed up to claim a new hill for both of us.  Once at the summit the Trimble was quickly set up to gather data, and away to the west the rain front was now depositing its wet stuff on a part of the Moelwynion, so we knew that we hadn’t beaten it and in all likelihood we were going to get wet.

One summit left to visit with Moel y Croesau in the background

The rain massing beyond Trawsfynydd

Gathering data at the summit of Pt. 369.5m (SH 739 374)

The Trimble set-up position at the summit of Pt. 369.5m (SH 739 374)

Following a fence line steeply down beside the remains of a grassed over stone wall led us down to the connecting bwlch.  Thankfully the bwlch was tight and therefore minimum assessment was necessary, as I packed the Trimble away after its data collection the first wind-blown raindrops fell and we quickened the pace on the continuation of the green track that we had left to head up and bag the Trichant.

Gathering data at the critical bwlch of Pt. 369.5m

The path led past the expansive Llyn Hiraethlyn, which must be another forgotten lake seldom visited and yet tranquilly placed.  Contouring the land beyond the path led down toward the old railway line that once went to Y Bala, by now the drizzled raindrops had disappeared east and a slight bright spell developed and remained with us as we headed under the old railway line and down across summer growthed fields with views of Y Garn and past the old farm house of Bryn-celynog to my car.

Llyn Hiraethlyn

Pt. 369.5m (SH 739 374)

Passing under the old railway that once went to Y Bala

A fine view of Y Garn

We’d visited six hills in all and surveyed each summit and five bylchau with only the bwlch for Graig Wen remaining un-Trimbled, with this compact group of hills making a fine circuit and one that portray a wild scene of landscape.  

Survey Result:

Pen y Foel Ddu

Summit Height:  531.2m (converted to OSGM15)

Summit Grid Reference:  SH 75395 39452

Bwlch Height:  514.6m (converted to OSGM15)

Bwlch Grid Reference:  SH 75250 39548

Drop:  16.6m (Uchaf status confirmed)

Dominance:  3.13%

Foel Cynfal

Summit Height:  545.5m (converted to OSGM15)  

Summit Grid Reference:  SH 74998 39546

Bwlch Height:  517.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 74884 39528

Drop:  28.1m (500m Sub-Twmpau status confirmed)

Dominance:  5.16%

Pt. 548.6m

Summit Height:  548.6m (converted to OSGM15) 

 

Summit Grid Reference:  SH 74389 39398

Bwlch Height:  532.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 74328 39295

Drop:  16.2m (Uchaf status confirmed)

Dominance:  2.95%

Graig Wen

Summit Height:  555.6m (converted to OSGM15) 

 

Summit Grid Reference:  SH 73910 39474

Bwlch Height:  414.6m (converted to OSGM15, from subsequent Trimble GeoXH 6000 survey)

Bwlch Grid Reference:  SH 76301 40330

Drop:  141.0m (Submarilyn addition)

Dominance:  25.38%

Moel y Croesau

Summit Height:  490.6m (converted to OSGM15)  

Summit Grid Reference:  SH 74812 38345

Bwlch Height:  456.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 75052 38555

Drop:  34.2m (Pedwar status confirmed)

Dominance:  6.97%

Pt. 369.5m

Summit Height:  369.5m (converted to OSGM15) 

 

Summit Grid Reference:  SH 73944 37497

Bwlch Height:  338.8m (converted to OSGM15)

Bwlch Grid Reference:  SH 74077 37523

Drop:  30.7m (Trichant status confirmed)

Dominance:  8.31%

For further details please consult the Trimble Survey Spreadsheet

For details on the bwlch survey post of Graig Wen