Mapping Mountains – Trimble Surveys – Cadair Idris

23.05.18  Braich Ddu (SH 645 120), Ffridd Uchaf Cregennan (SH 647 128) and Craig y Merwydd (SH 644 134)

Ffridd Uchaf Cregennan (SH 647 128)

With a continued forecast for blue skies and warmth, I visited hills adjoined to the western part of the Cadair Idris range which are positioned above the small community of Arthog.  I thought three hills should give me my mountain fix, and with a fourth tagged on close to the Arthog Bog I would no doubt be a happy bunny by the end of the day.

I was walking by 8.00am having parked my car at a junction of minor paved roads adjacent to a track, with one leading north toward Arthog, one being the continuation of the road I had driven on and leading to the farm of Bron-lletty-ifan and the adjacent track leading south toward my first hill of the day.

The track leading toward Braich Ddu 

It was stunningly beautiful in the early light with hillsides ablaze in green and all beneath an iridescent blue sky.  In the distance the profile of Pared y Cefn Hir as ever stood out, whilst the great bulk of Tyrau Mawr shot skyward in a shimmering blue tinged silhouette.

Tyrau Mawr

The track led to the bwlch connecting Ffridd Uchaf Cregennan with Braich Ddu, with the critical point being on the gravelled track, and I sat in sunshine happy with life as the Trimble beeped away collecting its individual datum points.

Gathering data at the critical bwlch of Ffridd Uchaf Cregennan

I’d only visited my next hill; Braich Ddu once before in February 2000, I decided a direct ascent would be fun and followed a sheep path upward before crossing to the east side of the fence that steadily climbs this flank of the hill, in time I popped out on to leveller ground and regained my breath before continuing to the high point.

Watchful sheep

The summit ridge of Braich Ddu has now unfortunately been churned up by off-roaders with deep trenches where grass once grew; it’s a shame to treat a hill in such a way.

A sad reflection of the times

The Mawddach estuary stretched below with tidal sandbanks meandering amongst blue waters, with Fegla Fawr and Fegla Fach prominent as wooded landlocked islands.

The summit of Braich Ddu was easily identified and within a few minutes the Trimble was gathering its allotted data, once data were stored and the equipment packed away I continued down the hill’s broad south-westerly ridge to the gravelled track that I had left an hour or so previously, this swung around the northern section of the hill and led me back to the bwlch that I had earlier surveyed.

Gathering data at the summit of Braich Ddu

Approaching Ffridd Uchaf Cregennan

Above the bwlch to the north lay the summit of Ffridd Uchaf Cregennan and a slow plod up the hill led to its attractive summit, and within a few minutes the Trimble was sitting atop my rucksack with its internal antenna aligned with the high point of the hill and a measurement offset noted.

Gathering data at the summit of Ffridd Uchaf Cregennan

The ever present Tyrau Mawr

My route to the next hill was back down the inward track to my car, as I started walking up the continuation of the paved lane toward the next bwlch a quad bike appeared heading up the Arthog road from the north, I waved and walked back down the road and once the quad bike had reached me it stopped.

I spoke with Emlyn Lloyd for quite some time and could easily have carried on doing so as he proved a wonderful person to speak with, full of gently given knowledge and as with so many farmers who I’ve met over many years, only too willing to impart this knowledge.

Emlyn Lloyd

The hill I had just surveyed is a part of Emlyn’s land and is known as Ffridd Uchaf Cregennan, this is the highest ffridd of Emlym's farm; Cregennan, which is situated further along the narrow lane to the north.  He confirmed the name of my next hill; Craig y Merwydd, and gave me a name that other farmers had also given me when I started my place-name research many years ago, for the higher hill which is named as Braich Ddu on the map.

As I waved goodbye to Emlyn I followed his quad bike up the road to the connecting bwlch with Craig y Merwydd, the critical point was immediately below the narrow road in what was once either a stone built house that now lay beside the road in ruin, or an old sheepfold.

Gathering data at the critical bwlch of Craig y Merwydd

The morning was so becalmed in beauty that I was happily taking ten minute data sets instead of the customary five, being more than happy to sit in the sun and let my mind wander to all manner of things and places and listen to those distant and dim beeps as each datum point was stored, sometimes life can be a simple affair and this, I think, is one of the joys of the hills as they have capacity to strip away periphery detail and concentrate one’s mind on the here and now, which for me this morning involved quiet contemplation.

Just one summit remained to survey before I headed down to visit a vegetated landlocked island beside the Arthog Bog, and that summit was Craig y Merwydd. 

Craig y Merwydd is a rocky lump of a hill with two distinct summits and both were Trimbled.  Whilst data were gathered I sat below the high point looking out to sea in a stunningly beautiful land being warmed by sunshine cast out of a forever blue sky, it felt good to be alive.

Gathering data at the summit of Craig y Merwydd

Pared y Cefn Hir

Once data were stored and the Trimble closed down and packed away I made my way off the hill and back to the minor lane to my car and proceeded to drive north toward Arthog and my last hill of the day; Ynys Gyffylog.    

Survey Result:

Braich Ddu

Summit Height:  545.8m (converted to OSGM15)

Summit Grid Reference:  SH 64536 12066

Bwlch Height:  494m (spot height)

Bwlch Grid Reference:  SH 65371 11430 (spot height)

Drop:  52m

Dominance:  9.48%

Ffridd Uchaf Cregennan (significant name change)

Summit Height:  351.9m (converted to OSGM15)

Summit Grid Reference:  SH 64745 12858

Bwlch Height:  325.0m (converted to OSGM15)

Bwlch Grid Reference:  SH 64787 12795

Drop:  26.9m

Dominance:  7.65%

Craig y Merwydd

Summit Height:  295.7m (converted to OSGM15)

Summit Grid Reference:  SH 64413 13459

Bwlch Height:  261.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 64605 13317

Drop:  34.6m (200m Sub-Twmpau reclassified to 200m Twmpau)

Dominance:  11.70%

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Cadair Idris

17.02.18  Ffridd Nant y Gwyrddail (SH 674 147, only bwlch surveyed)

The bwlch of Ffridd Nant y Gwyrddail (bwlch at SH 662 134)

Having visited three hills close to where the critical bwlch of this hill lies I thought I should at least visit its boggy depths and obtain data, as this can be compared against the data that was gathered using a Leica GS15 when along with John Barnard and Graham Jackson we investigated this spot whilst surveying for the position of the critical bwlch of Pared y Cefn Hir (summit at SH 661 148).

It seems a long time ago when in November 2012 this bwlch was surveyed using the Leica equipment, as we had surveyed the summit of Pared y Cefn Hir and its adjacent hill of Bryn Brith, we needed to find the position of the bwlch connecting the higher of these two twin topped 383m map heighted hills to ascertain its drop value, and as the map indicated three positional possibilities for this critical bwlch, each in turn needed surveying, and the bog that makes up this potential bwlch position was by far the most soggy and unwelcome, to the point that after standing immersed in the bog operating the staff for about 45 minutes I thought I was suffering from trench foot!

Using level and staff in November 2012 to determine the bwlch position of Ffridd Nant y Gwyrddail

Today was an easy proposition in comparison as I had come prepared with the ten figure grid reference for this bwlch position.  When surveyed with the Leica GS15 this position proved not to be the critical bwlch of Pared y Cefn Hir (which proved by 0.09m to be the higher when compared to Bryn Brith), but it is still a connecting bwlch for another hill, and that hill is positioned down stream of this bwlch to its north-east with its summit given a map height of 312m at SH 674 147, the hill remains unnamed on the map but a visit to a local farmer after this survey gave the name of Ffridd Nant y Gwyrddail for the bounded land where the summit of this hill is situated.

It was only a couple of minutes’ drive from where my car was parked to where a passing place beside the minor road gave me an opportunity to leave the car for the short period of time this bwlch survey would take.

I was soon in the bog, thankfully wearing wellies this time, and used the Trimble as a hand-held device to zero in on the ten figure grid reference.  Even after doing this the underfoot conditions would still give a large margin of uncertainty to Trimble placement as tussock grass predominated. 

Gathering data at the critical bwlch of Ffridd Nant y Gwyrddail

As the Trimble ebbed down to the 0.1m accuracy level before data should be logged I watched as the delicate play of light slowly cast down upon adjacent hills, with the coned and pyramidal profile of Ffridd Bellau Nant y Gwyrddail looking particularly fine. 

Ffridd Bellau Nant y Gwyrddail (SH 665 139) on the left and Ffridd Nant y Gwyrddail (SH 674 147) on the right

Once the 0.1m accuracy level appeared I pressed ‘Log’ and waited for the allotted five minutes of data to be gathered.  My stay in the bog had been a short one, and especially so when compared to my last visit.  Once back at the car I drove the short distance down the valley and called at Nant-y-gwyrddail before visiting Emyr Rees of Tynyceunant.

Survey Result: 

Ffridd Nant y Gwyrddail (significant name change)

Summit Height:  311.5m (LIDAR)

Summit Grid Reference:  SH 67419 14719 (LIDAR)

Bwlch Height:  237.7m (converted to OSGM15, Trimble GeoXH 6000)  237.7m (converted to OSGM15, Leica GS15)

Bwlch Grid Reference:  SH 66210 13444 (Trimble GeoXH 6000 & Leica GS15)

Drop:  73.8m (LIDAR summit and Leica GS15 & Trimble GeoXH 6000 bwlch)

Dominance:  23.69% (LIDAR summit and Leica GS15 & Trimble GeoXH 6000 bwlch)

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Cadair Idris

01.05.15  Gau Graig (SH 743 140) 

Gau Graig (SH 743 140)

Cadair Idris was the second mountain I visited and I can still remember the thrill of discovering the beauty of its sculptured high cwm with Llyn Cau nestled in the cirque of cliffs and crags.  I consider that we then ventured up Cadair completely unprepared, as we took a party tent with us and pitched it beside Llyn Cau and brought more cans of lager than water.  Thankfully the evening was blissfully tranquil; otherwise the tent would have been easily blown to shreds.  The lager was drunk, we all had a great time and ascended the stone shoot to the summit the following morning in a variety of footwear including Doc Mart shoes, pumps and plimsolls.

This visit made a lasting impression and I re-visited in a similar manner a year or so later.  Following these two visits I invested in proper walking boots, maps and waterproofs and haven’t looked back since.  I have so many memories of these hills from sleeping in the summit shelter on three occasions to being dropped off at the top of the A487 and walking the full ridge, descending to Abermaw (Barmouth) and hitching back home.

The hills radiating out from Cadair Idris still draw me close with many fond memories from countless visits.  These hills are positioned from west to east with the summit of Cadair Idris; Pen y Gadair, centrally situated.  At the eastern end of these hills is Gau Graig, a 683m map heighted hill that is pyramidal in shape when viewed from its east.  The hill is steeply honed on this eastern side, it appears in a number of different hill lists, but the one that interested us today was its Hewitt and Sim listing, as it just scrapes in with a listed c 30m of drop.  I’d looked at the bwlch contouring for this hill on a number of occasions and had given Gau Graig c 28m of drop and therefore a Sub-Twmpau in my Twmpau list to the Welsh P30s.

Gau Graig had been suggested by John for us to survey, as Graham was on holiday we decided to just take a level and staff with us and have the Trimble as back-up to produce an absolute height for the hill and check its height values against the more accurate ones produced by the line survey.

We parked in the large pull-in area to the south-west of the high point of the A487 at SH 753 135.  From this car park a foot stile gives access onto a narrow but good path that leads north, gaining height as it does so before curving around to the west and following a fence up toward the steepening bulk of Gau Graig.

John on the lower section of Gau Graig

On our way we came upon Ian Tether who had travelled from Anglesey, he was wrapped up and seated, waiting for the military aircraft that use this high pass as part of their Machynlleth loop.  Across the valley at the top of the Craig y Llam cliffs were other people doing likewise, I’d already driven past an almost full car park at Bwlch Oerddrws when on my way to meet John, and these people were also out on the lower hillside waiting for the low level fly past of the military aircraft.  We stopped and chatted with Ian for a few minutes before continuing up beside the fence.

Ian Tether wrapped up waiting for the military aircraft

The ascent of Gau Graig from this direction can be a bit of a lung buster as the higher one gets the ground gets steeper with the final part through a rock band before the ground levels off just before the summit.

The ground is just about to get a wee bit steep

Once at the top we put on extra layers of clothing as although the forecast was for sunshine shielded by high cloud and for the day to be dry, a chillingly blown easterly wind was sweeping across the hills.

Mynydd Moel (SH 727 136) from Gau Graig

We had come well prepared with ten figure grid references for two potential bwlch positions which had a small intervening bump between, the furthest of these positions from the summit of Gau Graig also had a 659m spot height on the Ordnance Survey enlarged mapping on the Geograph website.  If the position of this spot height was at the critical bwlch and if this and the summit spot height were accurate the hill would only have 24m of drop and not the c 30m given in the Hewitts and Sims listing.

Before starting the line survey we set up the level and took readings to two rocks beside the cairn that appears overlooking the northerly part of this hill’s summit area, and onto a prominent rock positioned much closer to the fence that we had followed upto the summit.  The latter proved higher, the rock is positioned approximately 40 metres from the fence as opposed to the cairn which is probably about 140 metres from the fence.

Having found the high point we gathered five minutes of data with the Trimble and walked down to the area of the bwlch.

Gathering data from the summit of Gau Graig with the cairned top in the background

The Trimble GeoXH 6000 at the high point of Gau Graig with Mynydd Moel in the background

John had input the two ten figure grid references for the potential bwlch position into his hand-help GPS and when down in the area of bog that constitutes the bwlch we found that the nearest one to the summit of Gau Graig was close to a small pool, whilst the other was beside a ladder stile.  We took readings to the two and found the one beside the pool to be approximately 0.5m lower than the one beside the ladder stile, therefore we could dispense with more accurate surveying at the farthest option and concentrate our efforts around the confines of the small pool, and as you can imagine these were generally a bit squelchy.

If the spot height on the Ordnance Survey enlarged Geograph map was correct it would mean that the critical bwlch was approximately 0.5m lower than 659m, therefore giving the hill only 24.5m of drop, and therefore we already knew that there was a probability that Gau Graig would be deleted from the Hewitt and Sim ranks.

Having found that the small pool option was where the critical bwlch lay, we positioned two lines of flags at 2 metre intervals running across the bwlch from two valley to valley directions and took readings at each flag, this told us that the direction of the hill to hill traverse intersected the fence and the critical bwlch lay beside the pool on its north-westerly side.

The first line of flags positioned across the bwlch on the valley to valley traverse

We left three coloured flags at this position and started line surveying up toward the summit.  John operated the level and noted the readings whilst I held the staff.  Nearing the summit and we both thought that the hill didn’t have the required 30m of drop and 75 minutes after starting the line survey we took the last reading onto the high point of the rock that we had already determined to be the summit of the hill.  As John did the sums I did a pan around with the video camera and went to John to film him giving the result.

The result is that Gau Graig has 25.7m of drop and if confirmed by Alan Dawson the hill will become a Sub-Hewitt and Sub-Sim.  We had considered doing a line survey back to the three flags at the bwlch to ascertain a closing error, but the margin of drop dictated that this wasn’t really necessary. 

Before leaving the summit I took a few photos of John with the staff at the high point of the hill, and we then walked back down to the bwlch where John gathered ten figure grid references with his hand-held GPS and I positioned the Trimble on its improvised tripod and gathered five minutes of data.

John at the summit of Gau Graig

Gathering data at the critical bwlch of Gau Graig

John noting the ten figure grid reference for the bwlch with his hand-held GPS

All we now had to do was reverse our inward route back through the steep rock band and down beside the fence toward the waiting car.

Reversing our inward route down through the rock band and the steep section

John with the cliffs of Craig y Llam in the background

The last steep section before the path levels off

It had been another excellent day on the hill and another result which will mean a status change for a hill in two lists, three if you include the Tumps.     

 Survey Result:

Gau Graig

Summit Height:  683.8m (converted to OSGM15)

Summit Grid Reference:  SH 74373 14023

Bwlch Height:  658.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 73913 13777

Drop:  25.4m (Trimble geoXH 6000) 25.5m (Line Survey) (Hewitt reclassified to Sub-Hewitt) (Simm reclassified to Subsimm) (600m Sub-Twmpau status confirmed)

Dominance:  3.71%

For further details please consult the Trimble survey spreadsheet click {here}