Saturday, 21 May 2016

Mapping Mountains – Trimble Surveys – Pumlumon

05.05.16  Graig Fach (SN 821 931), Banc Bugeilyn (SN 826 924), Foel Fadian (SN 828 953, bwlch only), Bryn Llwyd (SN 835 920) and Bryn yr Ŵyn (SN 839 925)

Foel Fadian (SN 828 953)

The northern Pumlumon is a land of open big sky where during spring the accompaniment of Skylarks and a grazing sheep are usually the only living creatures heard and seen.  These hills are wonderful places where moor and bog meet and sun drenched bleached hillsides are interspersed with the darkened sprig of heather.  It was to these hills I ventured today; I hadn’t been this way in a number of years but had wanted to re-visit ever since getting the Trimble as one hill in particular needed a detailed survey.

The track to the car park beside the beautiful lake of Glaslyn is now rutted and puddle laden and I would no longer take anything except for a four wheel drive vehicle down it.  As I locked my car I looked at my watch – 7.34am – a relatively early start and the slight chill set against the blue of sky was a delicious feeling, and especially so when looking south toward the continuation of the track to Glaslyn, as a track meandering in to the hill is a welcoming site, one that fulfils many dreams.

A track to the hills - a sight that fulfills many dreams

I’d come with a set plan for the day and fully realised that it may be a long one as I knew there were many surveys to conduct; 25 as it turned out, which for me and my Trimble equalled my record.

Setting off on the track brought back many memories from my previous visits, all good ones, memories can be like friends on occasion where their presence evokes the past with inner smiles and heart felt sharing’s of time gone by that is renewed with each meeting.

The first survey of the day was on the track, beside one of the many rutted puddles next to the entrance to where cars can be parked to view Glaslyn.  This point is the critical bwlch for Banc Bugeilyn.  As the Trimble gathered its data I stood and soaked in the scene as Foel Fadian leapt skyward, a hill whose summit I’d surveyed when with Eryl in January 2014 shortly after getting the Trimble, and the elongated profile of Cadair Idris filled the backdrop of mountain and moor.

Gathering data at the critical bwlch of Banc Bugeilyn

The elongated profile of Cadair Idris with the blue waters of Glaslyn as foreground

Passing Glaslyn its waters shone back with a succulent blue that matched the sky, a welcoming blue, a blue that screamed out to be noticed, a blue that foretold a good day on the hill.  I smiled at a notice close to the lake which read ‘Conditions underfoot away from the main path can be dangerous due to uneven and boggy ground and visitors should be aware of tripping or falling especially around the lake.’  This sums up the wilds of the northern Pumlumon as it can be a teense tussocky and a wee bit boggy in places.

The first hill on my surveying to do list for the day was Graig Fach, this is a forgotten lump beside the main track as it weaves its way in to the wilderness, it stands forlorn of its neighbouring higher hills, probably seldom visited but it has a beauty that comes with this, a beauty that this morning gave me a contented 50 minutes as I pottered about taking two data sets at the summit and likewise at the bwlch.  I’d only visited this hill once before, in May 2004 and it is currently listed as a Pellennig and an Uchaf, with the former based on remoteness and the latter based on a criteria of 500m minimum height and 15m minimum drop.

Surveying for summit height and position on Graig Fach with the Aran in the background

Rising above me to the south-east stood Banc Bugeilyn, a great lump of moor, heather and bog whose summit area consisted of five or six potential high points, all of which I planned on surveying.  I knew a good narrow path existed from the track to the summit, but having visited Graig Fach I did not want to double back to try and find it, so I plodded up its slopes and found a sheep track taking me in the right direction, this bi-passed a particularly large and ruddy coloured bog and led me to the steepening summit slopes.  Behind me the waters of Bugeilyn glistened in the morning’s blue skied heat with Llechwedd Crin standing invitingly steep above.

Graig Fach (SN 821 931)

Llechwedd Crin (SN 816 922) rising above the waters of Bugeilyn

Once on top I decided that at least four potential high points needed Trimbling, I eventually took data from five separate points and left happy in the knowledge that time had been spent doing this as a number of people have expressed doubt over the exact high point of this hill.

Gathering data from one of the five points surveyed for summit position and height on top of Banc Bugeilyn

Beyond Banc Bugeilyn is a drop southward in to the confines of a large and bog ridden bwlch.  This bwlch was impregnated in my memory as stretching wide and featureless.  I found that it had not changed since my last visit, I wandered to and fro assessing the land and surprisingly it wasn’t difficult to pinpoint the approximate position of the critical bwlch, this was at or between two stagnant pools.  As I stood almost ankle deep in water I set the Trimble up on top of my rucksack to give it elevation above the surrounding moor and bog, and once the 0.1m accuracy level had been attained I splashed my way a safe distance from it and tried to find relatively dry ground to stand on.

Gathering data at the critical bwlch of Foel Fadian

As the Trimble did its stuff I noticed a white Landrover on the track to my west, two people got out of it and made their way down steepening slopes, their voices carried toward me in the confined and yet open space of the bwlch, I thought it a rather comforting experience seeing another person, in this case two, a welcome addition that took my mind away from the detail catalogued for each survey that can become a slight burden on occasion.  I wondered who they were and what they were doing, they slowly inched their way down the slope and disappeared from view for evermore, their purpose and destination to remain a mystery, a metaphor for life itself as one meets / sees so many people during the years on this earth and the vast majority are unknown and will never be seen again.

After packing the Trimble away I sploshed my way across the bwlch to drier ground where a sheep track took me on to the bleached moor above the next bwlch that needed surveying.  This bwlch connects with Bryn Llwyd (this is a locally known name, used in preference to Esgair Greolen which appears on Ordnance Survey maps) and Bryn yr Ŵyn, both of which are given small uppermost 500m contour rings and no spot height on current Ordnance Survey maps.  I’d surveyed these hills on 11th July 2000 with my old wooden staff and afterward sent the results to Michael Dewey who then included Bryn yr Ŵyn in his listing to ‘The 500-Metre Tops of England and Wales’.  I’d found on that day that the summit of Bryn yr Ŵyn was slightly higher than that of Bryn Llwyd, this was a surprise as the latter has a larger uppermost 500m ring contour on Ordnance Survey maps, the difference was only 4ft which is well within the experimental error associated with the rudimentary surveying method employed on the day.  Having the Trimble enabled me to re-survey each hill and ascertain an accurate height, and in the process confirm which is higher and also survey the drop for the hill, which I knew would be close to the minimum 30m required to qualify for Michael’s list.

I took three data sets from the bwlch, two on the hill to hill traverse and one where contour interpolation suggests the critical bwlch to be positioned.  The ground hereabouts was relatively easy to survey, and as the Trimble gathered data I luxuriated in the warmth of the day under expansive blue sky.  During this time I looked out at the valley where I planned on walking through after surveying the two summits of Bryn Llwyd and Bryn yr Ŵyn, this encloses Cors yr Ebolion, which translates as the bog of the foel, the valley stretched away in to the distance, between me and it was just moor, and more moor, a never ending wilderness where openness predominates and lost souls can never be found.

One of three surveys conducted at the bwlch for what proved to be the connecting bwlch to Bryn Llwyd and not that for Bryn yr Ŵyn

After surveying the bwlch I plodded up to the summit of Bryn Llwyd, assessed the lay of land, chose the spot to place the Trimble and set it up to gather its customary five minutes of data.  One of the joys of having the Trimble is that the surveys can form part of an extended walk, instead of purposely going out to survey a single hill, this may sound a rather unusual statement, but having the Trimble enables you to do a hill walk and survey on the way, these two ways of surveying hills are very different beasts, both have their advantages, but due to its portability and its internal antenna, accurate data that is far better than what is on a map or what can be estimated from contour interpolation can be achieved with no more than a five minute data set, it’s a wonderful bit of kit and one that has proven to be a fine addition to my hilly wanderings.

Gathering data at the summit of Bryn Llwyd

After surveying the connecting bwlch between Bryn Llwyd and Bryn yr Ŵyn I continued to the summit of the latter and proceeded to take a further three data sets, all from the same position, the resulting data can be averaged after processing.  With three bwlch and three summit data from Bryn yr Ŵyn and a data set from the summit of Bryn Llwyd I left a happy bunny and followed the edge of the conifer plantation that swamps this hill’s northern slopes down to Cors yr Ebolion.

Gathering data at the summit of Bryn yr Ŵyn

Once beside the bog I balanced over old pieces of fence post left to cross a reed infested steam and walked slowly through tussocks and bog to the safety and delights of a contouring path heading northward.  Reaching the path I tried to stop my brow from sweating and sat down on the edge of the path had a drink and a bite to eat and took my fleece coat off for the remainder of the day.  I’d been on the go for almost six hours and still had almost three hours until I got back to my car, 25 surveys takes a lot of time, you know!

The path proved a saviour and I had a memory that I’d been on it once before, it led through the mayhem of moor and bog to the Nant Ddu, where it crossed the stream and joined a track which I followed down to a large farm building.  After being in the openness of moor for a number of hours the enclosed nature of these streams where the Nant Ddu, Nant Goch and the Afon Clywedog meet was a surprisingly refreshing experience, giving a different perspective for the eye to concentrate on.  The waters rippled down small waterfalls and glistened back as the sun cast down.

The western slopes of Y Grug

A stout and relatively new footbridge crosses the stream below the large barn and a gravelled track leads up on the other side.  I followed the track as it narrowed and gained height until reaching a fence, where I diverted up to the summit of Y Grug, a 520m map heighted hill that I’d visited previously and surveyed with the old wooden staff.  By now the day’s exertions were taking their toll and as the Trimble gathered data from the summit of Y Grug I munched on an apple and spotted my car beside the road off in the distance. 

As I left the summit my right ankle began to hurt at it rubbed against my still relatively new walking boots, a problem I’ve faced ever since getting them, although unwelcome I will persevere as I’ve encountered this with previous pairs of boots and they have always bedded in over time.

The ridge of Y Grug stretches north over two other summits, both with little prominence but as I was there and as I had the Trimble I quietly surveyed each point in turn and eventually made it back on to the road just over a kilometre from where my car was parked.  I only had one survey remaining to conduct, and this was close to the road in a field and was the critical bwlch for the last summit north of Y Grug.  After packing the Trimble away I plodded back on the road to my car, it had been an excellent day on the hill with some interesting survey results anticipated.

Survey Result:

Graig Fach

Summit Height:  513.1m (converted to OSGM15)

Summit Grid Reference:  SN 82140 93168

Bwlch Height:  498.6m (converted to OSGM15)

Bwlch Grid Reference:  SN 82317 93309

Dominance:  2.83% 

Banc Bugeilyn

Summit Height:  550.1m (converted to OSGM15)

Summit Grid Reference:  SN 82659 92441

Bwlch Height:  476.7m (converted to OSGM15)

Bwlch Grid Reference:  SN 83158 94286

Drop:  73.3m

Dominance:  13.33%

Foel Fadian

Bwlch Height:  475.0m (converted to OSGM15)

Bwlch Grid Reference:  SN 82848 92131

Drop:  88.9m

Dominance:  15.76%

The result of the processed data for Bryn Llwyd and Bryn yr Ŵyn was of sufficient interest to warrant another survey, and therefore the following detail takes in the combined results from each survey:

Summit Height:  501.4m (converted to OSGM15, and average of four surveys and Dewey and Uchaf status confirmed and summit relocated from Bryn yr Ŵyn [SN 83919 92571] and new Pellennig hill qualifying on distance) 

Summit Grid Reference:  SN 83574 92022

Bwlch Height:  471.2m (converted to OSGM15)

Bwlch Grid Reference:  SN 83220 91901

Drop:  30.3m (500m Twmpau status remains)

Dominance:  6.04%

Bryn yr Ŵyn

Summit Height:  499.9m (converted to OSGM15, and average of five surveys and summit relocated to Bryn Llwyd [SN 83574 92022])

Summit Grid Reference:  SN 83919 92571

Bwlch Height:  490.0m (converted to OSGM15)

Bwlch Grid Reference:  SN 83565 92279

Drop:  9.9m

Dominance:  1.99%

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