Mapping Mountains – Trimble Surveys – Y Berwyn

21.06.14  Mynydd Tarw (SJ 112 324), Pt. 687.9m (SJ 102 330), Foel Wen (SJ 099 334), Tomle (SJ 085 335), Cadair Fronwen (SJ 077 346), Craig Berwyn (SJ 071 323), Moel Sych (SJ 066 318), Pt. 694.7m (SJ 080 317) and Godor (SJ 094 307).

The high Berwyn, (L-R) Moel Sych, Craig Berwyn and Cadair Berwyn

Living in Welshpool the nearest ‘big’ walk for me is the Maen Gwynedd Horseshoe.  I’ve done this walk many times, with past and present hill walking friends as well as on numerous occasions by myself.  I’ve also surveyed some of the small prominence hills on the horseshoe with my old staff for possible P15 status, but I’ve never set out with the intention of surveying all eleven hills and ten bylchau that take in the whole horseshoe. 

The main advantages of using the Trimble is its internal antenna which enables accurate results to be attained with the use of one piece of equipment which weighs just 2lb, and staggeringly these accurate results can be attained with just two minutes of data collection, I knew from past experience that when planned survey points exceed ten the time on the hill dramatically increases, as even though the minimum of data I collect is five minutes it takes quite some time to walk the surrounds of a bwlch and determine its most likely position.  With this in mind I wanted to visit the eleven hills above Cwm Maen Gwynedd on a day that had long daylight hours and with the weather forecast set fine and dry.  Today was the day as it was the 21^st June and the forecast was for dry weather, with fair weather cloud in the afternoon and a slight northern breeze which would dampen the heat of the day.

As I drove toward Llanfyllin the high Berwyn were in cloud, this extended out from the west and north like a roughly rolled piece of dough.  I parked at SJ 118 306 where a couple of cars can easily be pulled off the road next to a small bridge that crosses the Afon Iwrch (roebuck river), a name that conjures times when the land was different to nowadays.

I’d brought all manner of surveying implements with me, including a pole, clamp, steel tape, two Tupperware boxes, draughts board, dog lead and of course the Trimble.  I imagined I may need them all, thankfully I didn’t use the Tupperware, draughts board or the dog lead, all of which may have caused a few eyebrows to be raised by any passing hill walker.

Except for the occasional bark of a farm dog and the gentle flapping of overnight washing hanging out to dry, the countryside was quiet as I set off walking at 7.50am.  The route to the first hill of the day; Mynydd Tarw, goes through two farm yards before access to the hill can be gained. 

Passing through one of the farm yards on the way up to Mynydd Tarw

The distinct triangular wedge of forestry on the south-eastern side of Mynydd Tarw has now been cut on its lower section, leaving the customary assault course of tree stump and rutted land.  As I gained height the remnants of early morning cloud was pushed across the sky by a strong north wind.  I was sheltered from this approaching from the south but once on the summit I had to put my summer one skin jacket and thin gloves on as hanging around waiting for surveying equipment to gather data can sometimes be a chilly business.

At the summit of Mynydd Tarw I had a good look around the base of the ancient Bronze Age summit cairn which has now been fashioned to incorporate a wind shelter and prodded a number of rocks, all moved, I then contemplated placing the Trimble next to a high wooden pole across the fence close to the forestry but as I was trying to establish the highest permanent land I decided upon the inside of the wind shelter.  This wasn’t ideal for the Trimble as it was now inside a walled canyon of rock so the results will be interesting, as a safeguard I also gathered data from one of the upper rocks of the wind shelter and measured the offset with the steel tape to its base.  During data gathering I came across a large furry caterpillar and almost squished it when I forgot about its presence when I clambered over the adjacent fence.

Gathering data at the summit of Mynydd Tarw (SJ 112 324)

A big furry caterpillar

The continuation of the walk follows the ridge fence in a north-western direction on a peaty path amongst heather.  This path can become a quagmire during winter time; today it was almost bone dry and effortless, a sheer joy!  The first bwlch of the day proved interesting as I stumbled around in heather trying to make sense of where the valley to valley traverse reached its high point.  Most bylchau are relatively easy to judge where the hill to hill traverse low point is, it’s the valley to valley direction that seems to cause the problem.  Once the set up position for the Trimble was found I gathered five minutes of data and headed up toward the next hill which the Nuttalls list as Foel Wen South Top.  I’m using the Pt. notation for its name until our planned P15 hill list is published, this will incorporate its locally known name and all P15 data that the Trimble produces.

Gathering data at the summit of Pt. 687.9m (SJ 102 330) with (L-R) Moel Sych, Craig Berwyn, Cadair Berwyn, Tomle and Cadair Fronwen in the background

The summits and bylchau were now coming in quick succession, as next was another bwlch where the first hill walkers of the day passed me, they were doing the horseshoe and no doubt would complete the walk many hours before me.  Next was the summit of Foel Wen followed by its critical bwlch.

The summit of Foel Wen (SJ 099 334) looking back at Pt. 687.9m and Mynydd Tarw

Foel Wen from the approach towards Tomle

The next part of the walk follows the ridge fence as it ascends over 100m to the summit of Tomle.  I gathered data from two points on the summit area, one on the northern side of the fence close to where the 742m spot height appears on the Ordnance Survey enlarged Geograph map, and the other next to the cairn which is on the southern side of the fence.  As the Trimble gathered its data I stood and looked out toward the high ridge with the profile of Craig Berwyn dominating, away across the upper reaches of the Nant Cwm-llawenog stood my next summit; Cadair Fronwen.  Between me and it was another bwlch.

Gathering data at the first option for the summit of Tomle

Gathering data at the second option for the summit of Tomle

Bwlch Maen Gwynedd is situated between Tomle and the main Berwyn ridge and is part of an ancient route that has probably been in existent for millennia, it now has a metal gate on it which the Trimble didn’t like as its first placement was so close to it that the required 0.1m accuracy before the time when data can be logged could not be attained, I replaced it and waited, once achieved I pressed ‘Log’ and ran away as quickly as possible as I didn’t want to obstruct any satellite signals.  Just on the west of the bwlch is an old standing stone, marked as a Boundary Stone on maps, it lay on the ground for many years but with assistance from local farmers it is now embedded back in its rightful place overlooking the bwlch.

Gathering data at the critical bwlch of Tomle

The old boundary stone just above the bwlch with Cadair Fronwen in the background

My route now headed toward the bwlch which is the low point between Cadair Fronwen and the higher Berwyn.  Another metal gate gave access to the land on the west of the fence, I examined the bwlch for quite some time as the continuation of the route toward the top of Cadair Fronwen has railway sleepers on part of it to encourage walkers to keep off the eroded quagmire of bog.  These railway sleepers also cross the bwlch, I thought the task of finding the bwlch position would be easy but a narrow grass gully also crossed the track just to the south of the gate.  It was the high point of this grass gully that I chose and once five minutes of data had been collected I headed up to the summit of Cadair Fronwen.

Gathering data at the critical bwlch of Cadair Fronwen

Another fine and ancient cairn is placed on the high point of Cadair Fronwen, this was once rounded, and unfortunately one side has now collapsed giving a sprawling appearance, but still a marvellous place for our Bronze Age descendants to erect such a monument.  I found land just on its northern periphery to be the highest.

At the summit of Cadair Fronwen (SJ 077 346)

I retraced my steps to the bwlch and headed up toward the main Berwyn ridge.  I’d now been out for over six hours and surveyed five hills, I estimated that the walk with its accompanying surveys may take twelve hours which would mean getting back to the car for 8.00pm, giving two hours leeway as darkness would overtake me at 10.00pm.  However, I was reassured as once high on the ridge the next three summits and two bylchau came quick and fast.

Approaching Cadair Berwyn

Cadair Berwyn is marked with a trig pillar and a map height of 827m (826.922m to the flush bracket in the OS Trig Database), it has the same metric map height as one of its neighbours; Moel Sych.  Old imperial maps used to show Cadair Berwyn as 2712ft and Moel Sych as 2713ft, these same imperial maps never recognised that the peak in between; Craig Berwyn, was in fact higher.  I hoped that today would give a good data set for each hill, one that could be compared to the old imperial heights and confirm which out of Cadair Berwyn and Moel Sych in the higher.

As the Trimble gathered data next to the trig I sat beside a fence stile and ate a sandwich, resting in beautiful surroundings where sky and earth meet and the sound of sky lark song as accompaniment.

Gathering data beside the trig on the summit of Cadair Berwyn (SJ 071 323)

The bwlch between Cadair Berwyn and Craig Berwyn has an elongated pond on it, the Ordnance Survey have chosen the eastern side of this pond to place their 808m spot height.  I found the eastern side of the pond to probably be the outflow, as conditions were dry no water was escaping the pond today, but the land on the eastern side led down from the peaty remnants of the pool.  On the western side of the pool is the continuation of the ridge fence, positioned away from the drop over the cliff edge.  The murky water ebbed up to the fence but land on the opposite side was just a bit higher, signifying that the critical bwlch lay to the west of the pond and not at its east.

At the start of the walk I had decided to gather five minutes of data from each summit and bwlch, this has become customary for bwlch placement, but I normally gather ten minutes of data from each summit.  But with over twenty data sets to take during the walk I had decided to restrict the amount of data from each summit, otherwise I may become a surveying benightment, forever lost in a Berwyn bog.  However, I had all intention of collecting at least ten minutes from the next summit as no accurate absolute height has ever been given to the high point of Y Berwyn.

The high point of Y Berwyn; Craig Berwyn was only recognised as such in the late 1980’s.  This is when I took up hill walking and I remember reading an article about Bernard Wright, a former motor oils scientist from Tarvin, Cheshire, who realised that the central peak on the main Berwyn ridge was higher that its two near neighbours; Moel Sych and Cadair Berwyn.  His accompanying friends suggested that the ‘new’ top should be named Craig Uchaf.  I remember reading this with a certain amount of excitement as the Berwyn is an extensive hill range and it seemed incredible that their highest point had only now been recognised, let alone that it did not have a name.  This however, was years before I had contact with local farmers and shepherds, people who have an intricate knowledge of the land that they work.  It seems that our world of hill bagging is somewhat insular and rather neglects local knowledge as the mountain has been thought of as the highest in Y Berwyn for decades and its name also known by local people.

As I approached the highest point where rock formations jut up out of the ground I wanted a few quiet moments to pay respect to my father, as it was from this point that some of his ashes were scattered, overlooking the land he knew as home.  When I reached the highest rock and looked over the edge there were two people sitting just below, I had a quick think about my Dad and started nattering away with them.  I explained about the Trimble and asked if they would be good enough to try and stay below it during data collection, this was no problem as they were happy enough where they were for a good while yet.

Although I’d visited this summit over 30 times I had no memory of the exact formation of the highest rock, I knew you could stand on it, but also knew when doing so you could easily over balance.  But was the very highest rock pointed, flat, or was it tapering?  I’d brought the infamous dog lead so I could attach it to the hand strap of the Trimble when it was gathering data, as if it then toppled off the rock I could save it from falling a few hundred feet over the edge.  The high point proved ideal for Trimble placement and with only a light breeze I judged that the dog lead was not necessary.  However, I did ask the two women if they saw it falling past them could they be good enough to grab it!  As it gathered its ten minutes of data I busied myself with more chat and a number of photos.

The Trimble GeoXH 6000 gathering data at the summit of Craig Berwyn (SJ 071 323), a summit whose accurate absolute height had intrigued me for a number of years

The Trimble perched on the very highest point of Y Berwyn

Safely nestled on the high point of Y Berwyn the Trimble gathers its ten minutes of data

Once ten minutes of data were safely stored we said our farewells and I sauntered off in the sunshine toward the bwlch between Craig Berwyn and Moel Sych.  This proved a problem and it was only at the fourth attempt that the Trimble attained its required 0.1m accuracy.  I eventually decided to attach the Trimble to its pole, but not with its external antenna.  I pushed the pole in to the ground, attached its clamp and the accompanying Trimble and waited for the accuracy to be attained before pressing ‘Log’.  This was the first time I’ve set the Trimble up like this so the result will be interesting, I measured the offset from internal antenna to the ground as 0.87m, this will be taken off the result after post processing.

Llyn Lluncaws below the eastern face of Moel Sych

The critical bwlch of Moel Sych, with Craig Berwyn in the background

The Trimble GeoXH 6000 attached to its pole gathering data

The next summit was Moel Sych where its  ancient summit cairn has undergone the indignity of being re-built as a half wind shelter, where only room for a couple of people sheltering from an eastern wind is possible.  Shame we can’t leave things such as ancient cairns alone without tampering with their appearance.  I checked on surrounding rocks and any that moved when prodded where dismissed for Trimble placement, I found the highest that didn’t and collected another five minutes of data.  All that remained were the three hills on the descending ridge.

Gathering data at the summit of Moel Sych (SJ 066 318)

I backtracked toward Craig Berwyn and followed the narrow path down toward the 698m map height summit of Moel yr Ewig, a name inappropriately used for the 695m map height hill to its east by many hill list compilers.  Just beyond the summit of Moel yr Ewig is the critical bwlch for the qualifying 2,000ft hill.  I lay in the heather as the Trimble gathered data and enjoyed the sun, safe in the knowledge that the surveying expedition would be completed before night fall.

I gathered data from two points at the 695m map height hill that the Nuttalls and Alan Dawson list as Moel yr Ewig.  Again I sprawled out in the heather enjoying the rest and looking out over Cwn Maen Gwynedd toward the hills I’d visited earlier in the day as the Trimble lay in the grass, bilberry and heather quietly gathering its all important data.

Looking south-eastward from one of the high points of Pt. 694.7m (SJ 080 317)

Looking north-westward from one of the high points of Pt. 694.7m (SJ 080 317)

Next stop was a bwlch that proved to be the most difficult of the day, this did not surprise me as I knew the land hereabouts but I had never gone off piste before, having always kept to the path that makes its way through the morass of heather and bog.  Once amongst the peat groughs and drainage channels I tried to evaluate the critical bwlch position to the best of my capabilities, it reminded me of a smaller version of the Meall Cala bealach that John, Graham, Alan and I had surveyed in July 2009.  As the Trimble gathered its five minutes of data I lay in the heather quite close to it as it was impersonating the proverbial needle in a haystack.

Just three surveys remained and the majority of fair weather cloud had dispersed, leaving a radiant early evening blue sky with pleasant giving warmth.  Soon data from the hill the Nuttalls list as Godor North Top had been gathered and I made my way down toward the last bwlch of the day.  I found a small land bridge that bisected two stagnant small bogs, placed the Trimble on some wet grass and settled down in the heather for my customary five minutes of laziness as it chugged away doing its stuff.  Just one hill to go!

Looking back at the high Berwyn from the summit of Pt. 675m (SJ 089 311)

The summit of Godor is crowned by a small quartz rock cairn with the high point of the hill just beside it.  As the Trimble received signals from orbiting satellites I soaked up the early evening’s light and thanked the hills for a marvellous day.  One I probably will never repeat on these particular hills, but a day that took me away from the ease of the path in to the heather bound confines of bwlch, and one that gave me a greater appreciation of these hills and the land that they are a part of.

Gathering data at the summit of Godor (SJ 094 307)

As the sun sank lower in the western horizon I contentedly made my way down in to Cwm Maen Gwynedd through fields of Buttercups and breeze blown swaying grass, with long shadows cast as the glow of evening light on adjacent hills illuminated the land.

Delicate evening light on grasses

Merging yellows with greens

Breeze blown swaying grasses

The ridge from Mynydd Tarw to Cadair Fronwen bathed in evening light

The path home

Shadows on a leaf

Looking back towards Godor as the sun sinks ever lower

The day’s totals proved a record for my Trimbe surveys with eleven summits and ten bylchau surveyed, and in all 25 data sets taken.  I arrived back at the car at 8.30pm, the surveying expedition having taken 12 hours 40 minutes.

Survey Result:

Mynydd Tarw

Summit Height:  679.4m (converted to OSGM15)

Summit Grid Reference:  SJ 11265 32439

Bwlch Height:  635.2m (converted to OSGM15)

Bwlch Grid Reference:  SJ 10755 32695

Drop:  44.2m

Dominance:  6.50% 

Pt. 687.9m

Summit Height:  687.9m (converted to OSGM15, from subsequent Leica GS15 and Trimble GeoXH 6000 survey)

Summit Grid Reference:  SJ 10232 33044 (from subsequent Leica GS15 and Trimble GeoXH 6000 survey)

Bwlch Height:  666.4m (converted to OSGM15)

Bwlch Grid Reference:  SJ 10100 33264

Drop:  21.6m (Leica GS15 summit and Trimble GeoXH 6000 bwlch) (Subsimm, Sub-Hewitt and 600m Sub-Twmpau status confirmed)

Dominance:  3.13% (Leica GS15 summit and Trimble GeoXH 6000 bwlch)

Foel Wen

Summit Height:  690.7m (converted to OSGM15, from subsequent Leica GS15 and Trimble GeoXH 6000 survey)

Summit Grid Reference:  SJ 09934 33407 (from subsequent Leica GS15 and Trimble GeoXH 6000 survey)

Bwlch Height:  631.7m (converted to OSGM15)

Bwlch Grid Reference:  SJ 09387 33625

Drop:  59.0m (Leica GS15 summit and Trimble GeoXH 6000 bwlch)

Dominance:  8.54% (Leica GS15 summit and Trimble GeoXH 6000 bwlch)

Tomle

Summit Height:  740.7m (converted to OSGM15)

Summit Grid Reference:  SJ 08529 33529

Bwlch Height:  719.8m (converted to OSGM15) 

Bwlch Grid Reference:  SJ 08087 33716

Drop:  20.9m (Subsimm, Sub-Hewitt and 700m Sub-Twmpau status confirmed)

Dominance:  2.82% 

Cadair Fronwen

Summit Height:  783.4m (converted to OSGM15)

Summit Grid Reference:  SJ 07754 34661

Bwlch Height:  710.1m (converted to OSGM15)

Bwlch Grid Reference:  SJ 07602 34085

Drop:  73.3m 

Dominance:  9.35%

Craig Berwyn (significant name change)

Summit Height:  832.0m (converted to OSGM15)

Summit Grid Reference:  SJ 07163 32351

Bwlch Height:  484.7m (converted to OSGM15, from subsequent Trimble GeoXH 6000 survey)

Bwlch Grid Reference:  SJ 01628 30532

Drop:  347.3m

Dominance:  41.74%

Moel Sych

Summit Height:  826.7m (converted to OSGM15)

Summit Grid Reference:  SJ 06627 31858

Bwlch Height:  792.8m (converted to OSGM15)

Bwlch Grid Reference:  SJ 06944 32140

Drop:  33.9m  (Simm, Hewitt and 800m Twmpau status confirmed)

Dominance:  4.11%

Pt. 694.7m

Summit Height:  694.7m (converted to OSGM15)

Summit Grid Reference:  SJ 08073 31773

Bwlch Height:  670.6m (converted to OSGM15) 

                   

Bwlch Grid Reference:  SJ 07743 31823

Drop:  24.2m  (Subsimm, Sub-Hewitt and 600m Sub-Twmpau status confirmed)

Dominance:  3.48% 

Godor

Summit Height:  679.2m (converted to OSGM15)

Summit Grid Reference:  SJ 09431 30747

Bwlch Height:  c 654m (interpolation) 

                   

Bwlch Grid Reference:  SJ 09107 30986 (interpolation)

Drop:  c 25m (Trimble sGeoXH 6000 summit and interpolated bwlch)

Dominance:  3.71% (Trimble GeoXH 6000 summit and interpolated bwlch) 




For details on the second survey of Foel Wen and Pt. 687.9m

For details on the bwlch survey of Craig Berwyn

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