Mapping Mountains – Trimble Surveys – Carnedd Wen

06.06.20  Y Golfa (SJ 182 070), previously Trimbled

Y Golfa (SJ 182 070)

When Aled and I stood atop Pen y Cerrig Serth on the 19^th January earlier this year I couldn’t foresee this as the last summit I would visit for almost five months.  The intervening time has brought a pandemic, the likes of which has not been seen for over 100 years.

The Coronavirus; Covid-19 has killed over 400,000 people worldwide and over 40,000 of these in Britain, and to combat its spread a lock down was instigated on the 23^rd March.  This is slowly being lifted throughout Britain, with firstly England taking the plunge of opening up with the other constituent countries of the UK being more circumspect.

Throughout the last 2½ months I’ve followed instructions and not travelled to take the allotted daily exercise instructed by the Welsh Government.  Therefore any exercise I’ve taken is from my own doorstep and hill walks farther afield must wait until the countryside is once again open.

Although many of the instructions due to the outbreak of Covid-19 are harsh, they are understandable and necessary.  This has obviously limited everyone’s hill walking, or at least those who have abided the instruction, as some unfortunately haven’t.

The outbreak and resulting limited scope for hill walking has reconnected me to my local landscape and enabled late evening walks from my doorstep, mainly using the towpath beside the Montgomeryshire Canal for access to the countryside.  But until this evening I had not visited a summit of a hill.  Over the last 2½ months I’d looked toward a variety of hills from elevated views above Welshpool as the main Berwyn ridge distantly looked back at me, and the Breiddin, Cefn Digoll, Yr Allt, Moel y Garth, Upper Park and Y Golfa all were on grand display.  These hills were always on show as the sunniest spring since records began gave two months of sunshine and increasingly warm temperatures.  However, the weather has now broke and rain has recently set in, with the temperature giving cooler conditions, and although this afternoon gave showers, the forecast for the evening was good.

I’d recently investigated public footpaths connecting the Frochas Lane with the estate grounds of Llanerchydol, and now wanted to use the latter as an ascent route to the summit of Y Golfa, which I had done on two previous occasions, the last of which when I Trimbled its summit in August 2014.

Setting off at 6.55pm the canal towpath gave access to the Back Lane which leads toward the Raven roundabout and the paved road heading west out of the confines of Welshpool, to the quiet pastured old estate grounds of Llanerchydol Hall.  As ever it was good to be out and especially so during an evening, which I rarely do when hill bagging.

The pleasantly warm conditions and cloudless deep blue skies of the last two months had been replaced with bubbled cloud and a cooling evening.  I hoped that I could watch a lowering sun from the summit before scampering off to find a descent route enabling a circular walk before darkness overtook me.

Upper Park on the left and Cromwell Hill on the right

The paved road leading through the old estate grounds gives a tranquil ascent route with grazing sheep and inquisitive cows a plenty.  This soon turns to a vehicle track as it gains height past Home Farm and Pen-y-golfa.  The continuing public footpath then heads across a field and beside the Golfa Wood before leading to a variety of green tracks high on the hill’s eastern flank, each through summered fern and undergrowth.

The Breiddin and Shropshire Plain beyond

Across the valley Upper Park and Cromwell Hill caught the last glimmers of sunlight, whilst farther to the east the Breiddin rose above the Shropshire Plain.  Appearing ahead of me the white trig pillar stood bolt upright signifying the high point of the hill.  I had hoped that low light would cast illuminated colour on the trig giving me opportunity for a number of photos framing it in the foreground with distant views beyond.  As I approached the sun sank behind a cloud bank out to the west leaving dulled colour on the hill.  I had missed my opportunity by no more than a couple of minutes; however I could not linger as it was now 9.00pm and I had to devise a descent route.

The summit of Y Golfa

Below me the Gaer Farm looked an inviting way to connect with the Frochas Lane, so off I scampered on more earthen tracks and narrower footpaths, past manicured golfing greens and eventually down a field to a track, past friendly horses and a relatively recent new paved road heading uphill to The Gaer.  From here I could, if I wanted, remain on a paved road all the way toward Welshpool.  However, I had a number of options available to connect with my home town, and one involved using the public footpath I’d recently been on that heads across fields to Lower Llanerchydol, this would also give me the shortest and quickest route back.

It was 10.00pm as I scampered across the fields toward Lower Llanerchydol.  The sun had sunk, leaving delicate mauved clouds peering across the sky.  The paved road through the old estate took me down to the Raven roundabout and the Back Road through Welshpool and finally the canal towpath where I was accompanied by dancing bats on my way back home.  Arriving at my front door I looked at my watch, it was 10.40pm; it was time for a large mug of tea and a contented sleep.

LIDAR image for the bwlch of Y Gofa

The following day I checked the Trimble result for the summit and examined the area of this hill’s bwlch via Google Maps before downloading LIDAR to see if the bwlch was covered.  It was, just.  I then spent an inordinate amount of time building up LIDAR contouring and comparing this to the digitised image on my laptop via the Google car.

The bwlch of Y Golfa, with the critical point just through the gate on the left, and across the field toward the fence.  Photo:  Google Maps

The contrast between a hill walk to a summit where data is then gathered and stored in the Trimble GeoXH 6000 and producing the same via LIDAR on a laptop is extreme.  One gives beauty and the other involves staring at a screen whilst tapping endlessly on a keypad.  However, the end result is accurate numerical data and this is presented below.

Survey Result:

Y Golfa

Summit Height:  341.4m (from previous Trimble GeoXH 6000 survey) 

Summit Grid Reference:  SJ 18247 07086 (from previous Trimble GeoXH 6000 survey) 

Bwlch Height:  175.1m (LIDAR)

Bwlch Grid Reference:  SJ 16645 06017 (LIDAR)

Drop:  166.3m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  48.72% (Trimble GeoXH 6000 summit and LIDAR bwlch)

For details on the summit survey of this hill

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Carnedd y Filiast

07.02.20  Foel Goch (SH 953 422), only bwlch surveyed

Venturing to north-west Wales for the weekend I decided that with the weather set fine for the day it was ideal conditions to survey a number of bylchau on the way.  The first of four surveys on the agenda was the bwlch that connects with Foel Goch.

The bwlch of Foel Goch

Foel Goch is situated between Y Bala towards its south and Cerrigydrudion towards its north and its summit was surveyed with the Trimble GeoXH 6000 less than three weeks ago, when along with Aled we traversed its easterly satellite peaks on a gloriously blue skied winter’s day.  That visit was my 22^nd to its summit and yet I had hardly paid its bwlch any attention at all, except to find it on a map and estimate its height to deduce the relevant drop value for the hill.  And yet I had passed it on a multitude of occasions whilst driving from Frongoch toward Cerrigydrudion.  During these times I drove past without a cursory glance and yet it was there, beside the road, just a few minutes’ walk from the B4501.  

Foel Goch (SH 953 422)

Many hill baggers, myself included, seemingly walk with proverbial blinkers on, as all that matters is the summit and that all important tick against yet another hill.  The connection between summit and bwlch and the drop therein is important for many classifications of hills, yet, the respective bwlch is seldom visited.

I’ve found since surveying with the Trimble GeoXH 6000 that visiting bylchau has an appeal all to itself.  This rather esoteric aspect of hill walking can take you to seldom visited places amongst the hills where just an occasional farmer or grazing sheep pass by.

Prior to visiting the Foel Goch bwlch I’d looked toward it from a digitised image produced by a Google car on my laptop, and noted a ten figure grid reference produced by interpolation of contours from the OS Maps website.  Parking was not ideal, as it seemed the only available place was on the B road, but as I hoped to be there relatively early in the morning and access through a gate toward the bwlch was on a straight part of the road I was sure this would not be a problem.

Fog clagged any view as I travelled west from Welshpool, and it wasn’t until cresting the top of the B4391 as it wound its way over the Y Berwyn, that conditions cleared with hill summits reaching upward in to blue sky.

I was parked beside the gate on the B4501 at 8.45am and soon had my wellies on, although the ground the other side of the gate as it led down a vehicle track through a grazing field didn’t warrant their protection as the ground was firmly frozen, as was the bog that makes up the bwlch.

By now the morning’s sun had crested the eastern horizon highlighting the small hills to the immediate west with beautiful colour, whilst the frozen ground I was now walking on remained in shade for another 20 minutes or so.

The bwlch stretched out orientated in a north-east to south-west direction, access to it was through another gate.  I walked its periphery looking up its reed grassed interior assessing the lay of land as I did so.  The valley to valley traverse gradually crept upward toward where a small flattened ridge entered the bwlch from the west and complimentarily where a broad grassed bank did likewise from the east.  I also noted this when driving prior to parking and considered the critical position of the bwlch to be near this point.  When in the frozen bog I marched back up it to set the Trimble up further to the north-east for its first of what I decided should be two data sets.  This would at least give a comparison of positions and heights from each point.

As the Trimble gathered its first data set of the day I stood beside a near fence and luxuriated myself in this quiet, seldom visited little spot, where an occasional car and farmers vehicle quickly disappeared off in to the distance on the B road as the sun crept on to the bog bringing morning colour to proceedings.

The first Trimble set-up position at the bwlch of Foel Goch

Closing the Trimble down as its allotted data were gathered and stored, I moved position back through the frozen bog and set the Trimble up for its second data set.  Before activating it to gather data I walked a short distance south-westward in to clumps of reed grass and peered back at the second set-up position; the land was heading uphill from me to it.  Happy with this second set-up position I set the equipment to gather data and stood fifty or so metres from it whilst it quietly beeped away gathering individual datum points.

The second Trimble set-up position at the bwlch of Foel Goch

Once the Trimble was safely packed away I headed on a direct route over two fences back toward the B road before the short walk to my car, it was now 9.30am and the second of the day’s four planned bwlch surveys was only a short drive further westward.  This second bwlch connects with Arenig Fach and is beside the A4212 as it speeds its way past Llyn Tryweryn. 

Survey Result:

Foel Goch

Summit Height:  611.0m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Summit Grid Reference:  SH 95379 42292

Bwlch Height:  336.8m (converted to OSGM15)

Bwlch Grid Reference:  SH 91716 43965

Drop:  274.2m

Dominance:  44.88%

  

For details on the summit survey of this hill

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Aran

13.09.19  Aran Fawddwy (SH 862 223), only bwlch surveyed

Aran Fawddwy is the highest hill in Britain south of Yr Wyddfa and as such it dominates the land around it.  The view from its summit is extensive with ridge upon ridge of diminishing hills to its east and the higher Eryri hills far off to its north.  I’d visited its summit 19 times but had never visited its bwlch, although I had driven over it on many occasions.  This bwlch is positioned beside the A494 road as it makes its way from Dolgellau in the south-west to Y Bala in the north-east.

Aran Fawddwy (SH 862 223)

The bwlch is unassuming, as many bylchau are.  Outside of the many vehicles that pass over it on a daily basis I wonder if anyone has ever visited it because of what it is.  I suspect not.

Prior to my visit Aled Williams had LIDARed the bwlch and afterward I did likewise.  I also drove a Google car in the vicinity of the bwlch to compare the placement of the bwlch via LIDAR to the lay of land via a digitised image, and found by parking at the entrance to Pant Gwyn on the western side of the road it would enable me to position the car directly over the position of the bwlch according to LIDAR.

LIDAR bwlch image for Aran Fawddwy

I arrived mid-afternoon and manoeuvred my car in to position leaving sufficient space for any vehicle driving in or out of Pant Gwyn, and importantly with the front of the car safely positioned off of the main road.

The car in place with the Trimble on its roof

Also crossing this point is the disused railway line that connected Dolgellau to Y Bala, its course can easily be seen either side of the road and before setting the Trimble up to gather data I wanted to investigate the land beside the road.  My conclusion is that the building of the rail line and road has increased the height of this bwlch from its natural point, but determining the natural height and its position is now probably impossible, therefore I concentrated on the LIDAR position and aligning the Trimble with it as it was placed on top of my car’s roof. 

The set-up position beside the grass verge next to the drive leading to Pant Gwyn

Once the offset between the Trimble’s internal antenna and the ground below was measured and noted, I created the file and waited for the 0.1m accuracy level to be attained and then pressed ‘Log’ and waited for the allotted data to be gathered and stored.

Gathering data at the bwlch of Aran Fawddwy

During this I stood back and watched the steady hum of cars hurtle past whilst enjoying the afternoon sunshine.  After the Trimble was closed down a vehicle appeared from Pant Gwyn, I went over to say hello and explain what I was doing, and the occupant said she did wonder.  We chatted for a number of minutes and she explained that her family farm from Rhyd-y-main and I wondered if I had made place-name enquires with her husband during the extensive enquiries with local famers when I covered the Aran range.

After I packed the Trimble and the surveying steps away I waved my goodbye’s and headed toward Y Bala and the B4391 road crossing the Y Berwyn for the last survey of the day.

Survey Result:

Aran Fawddwy

Summit Height:  905.6m (Leica RX1250)

Summit Grid Reference:  SH 86270 22386 (Leica RX1250)

Bwlch Height:  232.7m (converted to OSGM15)

Bwlch Grid Reference:  SH 85050 26799

Drop:  672.9m

Dominance:  74.30%

  

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Bannau Brycheiniog

13.09.19  Pen y Fan (SO 012 215), only bwlch surveyed

For many hill classifications the connection between the summit and bwlch of the respective hill is all important, as knowledge of each height gives the drop value of the hill.  This sounds simple, and usually in practice it is, however there are examples where the nature of the summit and that of the connecting bwlch come to the fore, and for Wales there are few other hills that can compare with Pen y Fan for the sometimes fraught nature of what constitutes a summit and also a bwlch.

Pen y Fan (SO 012 215)

Pen y Fan is the highest hill in south Wales and as such one can expect its connecting bwlch to the next higher summit to be a great distance from its high point, and this is so, with its bwlch situated towards the north close to or in the village of Talerddig.

For many years the summit of Pen y Fan had an Ordnance Survey triangulation pillar on its top.  Details in the OS Trig Database give a completion year of 1939; presumably this is when the pillar was installed.  The pillar was still in situ in 1990 but it was soon removed.  The summit of Pen y Fan now has a neatly arranged conical cairn at its high point, and adorning its top is a large upright flat rock with a fixed plaque giving the name and map height of the hill.  The old trig pillar had a flush bracket height of 886.358m and was set on a concrete base approximately 0.20m high, with natural ground at its base approximately 885.8m in height.

The trig pillar that once adorned the summit of Pen y Fan

I had visited and surveyed the summit of Pen y Fan on the 25^th October 2016, taking two data sets from the summit area, one at the top of the man-made conical cairn and the other on what I deemed to be the highest remaining natural ground of the hill.  These two data sets came to 885.739m at SO 01208 21582 and 884.601m at SO 01210 21587 respectively.  Dependent upon one’s view the 885.7m height from the top of the conical cairn can be taken as that for the hill as although the cairn is man-made it is nearer to the natural height of this hill when compared to the 884.6m height to remaining natural ground.  However, neither option is perfect.

Gathering data at the summit of Pen y Fan

Gathering data at the base of the man-made conical cairn at what can be deemed the remaining natural high point of the hill

The bwlch of Pen y Fan is to its north and placed close to, or in Talerddig, dependent again on one’s view of what constitutes a bwlch.  I had endeavoured to survey this bwlch on the 18^th August 2015 arriving in Talerddig early in the morning and proceeded to take a data set from where contour interpolation and an on-site inspection suggested the critical point to be positioned.  This point was in a field close to a house whose drive led toward the main road that passes through the village. 

Prior to data collection I had assessed the lay of land for a number of minutes, and had also done so after closing the equipment down and heading toward a gate which gave access to a drive leading to a house and which was beside the main road and a minor road where my car was parked.  When I reached the gate I looked back on my set-up position and wondered if it was correct, but with a big surveying day ahead that did not end until sunset I decided I was happy enough with the placement and headed south to examine the bwlch of Allt yr Esgair.

Gathering data at the 1st bwlch survey of Pen y Fan

Between then and now LIDAR has become available.  This has revolutionised hill classification in ways that those interested in such things could only dream of a few years ago.  Subsequently the bwlch of Pen y Fan was analysed via LIDAR by Aled Williams and the critical point was found to be beside the gate where I had looked back to the Trimble set-up position.

However, LIDAR also gives the opportunity to examine the lay of land in detail by building up contours at 1mm intervals if the inclination to do so takes a hold.  It also gives an opportunity to place accurate heights to such things as road and rail cuttings, something that contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps seldom do.  And just to add complication to an already fraught situation of what constitutes a summit and a bwlch, Talerddig just happens to have a rail cutting that when built was the deepest in the world.

LIDAR image of bwlch highlighted in white on right with the northerly part of the rail cutting highlighted in yellow on left

The rail line passing through Talerddig joined Machynlleth to Newtown and was constructed in the early 1860s.  The cutting is 37m deep (120ft) deep and must have been a difficult engineering task to complete.  Using LIDAR gives an opportunity to add an accurate height to this cutting as it makes its way southward up valley to the line’s high point before descending down valley toward Caersŵs.  The high point of the rail line to the south of the cutting would also be on the hill to hill traverse for anyone making their way from Pen y Fan to the next higher hill, and dependent upon one’s view should be taken in to account when calculating the drop value of this hill.  However, there’s no fundamental rights or wrongs with whether such things as cuttings should constitute a part of the drop value of a hill,  all one can do is assess the options and form an opinion, and if a different conclusion is formed by another person; respect it even though one may not agree with it.

LIDAR image of the rail cutting on left

LIDAR close up image of the rail line and the critical point of the bwlch highlighted in white

Therefore, we have a summit whose conical cairn is now man-made, although its height is nearer that of the natural height of this hill when compared to the highest remaining natural ground at the periphery of the conical cairn, and a bwlch that has a rail cutting which is lower on the hill to hill traverse compared to what may constitute the natural bwlch.  I say ‘may constitute the natural bwlch’ as when building up the contours with LIDAR I became aware that ground beside the house named Hafan that overlooks the field and gate where the Trimble GeoXH 6000 was previously set-up and where LIDAR places one position for the bwlch, looked as if it has been terra-formed as contours appear slightly ragged compared to their usual form.  The descending hill to hill contours also indicate that the bwlch should be placed near to where the Trimble was previously set up, although this is now on a descending route down valley from the gate where LIDAR places this option for the bwlch.  Having examined LIDAR in detail I concluded that the natural bwlch had been terra-formed and although a natural bwlch can still be followed up valley to ground at the base of the gate, the building of the house named Hafan had altered the lay of land sufficiently to disturb land where the natural bwlch was situated.

LIDAR close up image of the land leading to what could be deemed the remaining natural bwlch with the meeting of the white contour lines being the critical point; note jagged contours indicating the land has been terra-formed

Sometimes it is the surveying that is the simple task, with the dilemma of what constitutes a summit and bwlch being the difficult part.

Having surveyed what I thought to be the bwlch and with LIDAR indicating this option to be beside the gate I wanted to re-visit and as Talerddig was on route from the bwlch of Newydd Fynyddog which I had just surveyed to the bwlch of Aran Fawddwy which was my next port of call, I made my way over the hill road toward Talerddig. 

Having parked in the village, I walked the short distance to the gate with Trimble and surveying steps in hand and placed the Trimble atop the solid stone pillar adjacent to the gate and at the end of the drive leading to the house of Hafan.

The gate where LIDAR gives the remaining natural bwlch of Pen y Fan

I smiled as I looked over the gate toward where I had taken data from on my previous visit and quietly opened the gate to venture in to the field to take a measurement offset between the Trimble’s internal antenna and the ground in the field at its base.  Having noted a 1.51m offset I went back through the gate entrance, locked it behind me and stood on the surveying steps to set the file up in the Trimble, and once the 0.1m accuracy level was attained I pressed ‘Log’ and marched off toward the main road where I stood and took a few photos.

The Trimble set-up position at what can be deemed the remaining natural bwlch of Pen y Fan

Once the allotted data were gathered and stored I headed back to the surveying steps,  clambered up on them and pressed ‘Done’ and closed the equipment down, packed it away and headed back to my car, such a simple survey considering the complications of what constitutes the bwlch and summit of Pen y Fan. 

           

Survey Result:

Pen y Fan

Summit Height:  885.7m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Summit Grid Reference:  SO 01208 21582

Bwlch Height:  215.0m (converted to OSGM15, remaining natural bwlch)

Bwlch Height:  209.3m (LIDAR, rail cutting)

Bwlch Grid Reference:  SH 93136 00074 (remaining natural bwlch)

Bwlch Grid Reference:  SH 93041 99532 (LIDAR, rail cutting)

Drop:  670.7m (cairned summit and remaining natural bwlch)

Drop:  676.45m (cairned summit and rail cutting bwlch)

Dominance:  75.72% (cairned summit and remaining natural bwlch)

Dominance:  76.37% (cairned summit and rail cutting bwlch)

  

For details on the summit survey of Pen y Fan

For details on the 1st bwlch survey of Pen y Fan

For further details please consult the Trimble Survey Spreadsheet