Mapping Mountains – Trimble Surveys – Y Mynydd Du

13.06.17  Fan Brycheiniog (SN 824 220, only bwlch surveyed)

Gathering data at the bwlch of Fan Brycheiniog

Standing beside an A road watching cars and lorries thunder past a small piece of surveying equipment could be thought of as an unusual pastime, to many it undoubtedly is, but there is a satisfaction to such a thing, albeit an unusual one.

Having visited Mynydd y Drum and the Nant Helen Opencast Mine and with a small walk above Llanfair-ym-Muallt (Builth Wells) pencilled in for later in the day I thought I’d better survey the critical bwlch of Fan Brycheiniog; one of south Wales’ highest mountains.  This bwlch is positioned on or beside the A 4067 as it heads southward from Sennybridge toward Ystradgynlais, it was a bwlch I drove over earlier in the day and when doing so I tried to judge where its critical point lay.

Thankfully the road has a number of large pull-ins close to the area of the bwlch and once out of my car I went to work.  This work consisted of bending over, kneeling and sometimes lying on the ground assessing where the uphill from the valley to valley traverse meets the downhill from the hill to hill traverse.  When doing this it is advantageous to gain height for an overall view of the scene, unfortunately the ground to the east of the road is steep and therefore I used a conveniently placed ladder stile to stand on top of and gain a little elevation to assess the lay of land.

It proved easy to judge where the upper part of the northern valley lay as the reed grass and wet surrounds of the Blaen-crai was positioned beside the ladder stile, which was only a few metres from the road.  I marched back to the lay-by where my car was parked and proceeded to kneel on the grass verge to look at the uphill part of the road, there seemed to be two points where the high point may lie, with a slight dip in the road between.

I ummed and aghed for ten minutes or so wondering which out of these two points to gather data from, on the eastern side of the road a drainage ditch beside the grass verge helped in judging where the downward southern land lay, however as drainage ditches aren’t necessarily consistent in their depth I decided only to treat this as an indicator of where the critical point may lie.

During this process vehicles sped past, one thing was certain the Trimble was not going to be set-up on the road, perhaps if this bwlch was on a country lane it would be all right to do so, but a busy A road was asking for trouble.  Deciding on my point I set the Trimble up on my rucksack and measured a 0.42m offset between the equipment’s internal antenna and the ground at the base of the rucksack and waited until the 0.1m accuracy level was attained before data should be logged.

The Trimble set-up position at the bwlch of Fan Brycheiniog

During data collection I made a note of how many vehicles whizzed past heading south, the total amounted to eight cars and four Lorries, all within five minutes; hopefully the data set won’t be compromised by this activity.

Once the allotted five minutes of data collection were up, I switched the equipment off, packed it away and headed north to the outskirts of Llanfair-ym-Muallt (Builth Wells) and the joys of Garth (SO 053 506), a hill I’d wanted to visit for many a year.

Postscript:

Since this survey took place the details for the bwlch of this hill have been ascertained from LIDAR analysis conducted by Aled Williams, and these details are being prioritised in favour of those produced by the Trimble GeoXH 6000.

  

Survey Result:

Fan Brycheiniog

Summit Height:  802.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 82435 22060 (Trimble GeoXH 6000)

Bwlch Height:  378.5m (LIDAR)

Bwlch Grid Reference:  SN 87056 19547 (LIDAR)

Drop:  424.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  52.84% (Trimble GeoXH 6000 summit and LIDAR bwlch)

For details on the summit survey of Fan Brycheiniog

For further details please consult the Trimble Survey Spreadsheet

Mountain Biking the Hill Boundary of Powys - Day 6

25 years ago today I set off with a good friend; Mark, on the sixth day of our attempt to circumnavigate by bicycle Wales’ largest county; Powys.  To add interest to the venture we planned on visiting the highest point of each of the eight 2,000ft hill ranges within the county, which are all situated around its periphery, bikes included.  We were backed up by Hazel and Barry; without whom our little adventure would not have taken place.  Prior to setting off and during our trip we raised money for the British Heart Foundation and the Ystradgynlais Mountain Rescue team.

The following is an account of this ten day expedition with each day’s journey appearing on the Mapping Mountains blog 25 years after it had taken place.

The county of Powys with the eight 2,000ft hill ranges positioned around its periphery

Day 6

31.07.90 – Mynydd Du – Fforest Fawr – below the Brecon Beacons     

As we arrived at the camp site yesterday the sun had broken through the blanket of cloud and gave us a beautiful evening, the skies had remained clear overnight and when Mark unzipped the door of the tent this morning the warmth of the sun greeted us.  We were soon up and having breakfast and getting the bikes ready for another day on the hill.  Today’s hill range was Mynydd Du with its high point being Fan Brycheiniog.

After setting off we nearly overshot our intended junction and almost ended up in a dingle as we headed toward the hills, we stopped and examined the map and happy that we were on the right route carried on toward the track that approaches Llyn y Fan Fach.  This track would give us good access toward our intended hill.

We rode as far as the filter beds where a small fish hatchery is placed, the sun beat down which was a welcome addition when compared to our crossing of the Berwyn and Pumlumon, but the heat was unrelenting and slowed our progress.

We cycled as far up the track as we could and then contoured around the hillside aiming for the small path that climbs steeply up to Bwlch Blaen Twrch which is positioned between Picws Du and Fan Brycheiniog.  The slopes ahead of us seemed never ending and the bikes were slung over our shoulders as we edged our way up toward the bwlch.

Taking a rest below Picws Du

The heat starts to take its toll

Steep ground on the way up toward Bwlch Blaen Twrch

Beyond the bwlch we carried and pushed the bikes up the final slopes to the summit of Fan Brycheiniog where we rested, ate some food and took a couple of photos next to the trig pillar.  We had now reached the summit of four out of the eight hill ranges we planned on visiting and the next three high points of Fforest Fawr, the Brecon Beacons and the Black Mountains lay tantalisingly in view to our east.

Beyond the bwlch we pushed and carried the bikes to the summit of Fan Brycheiniog

Beside the trig pillar on Fan Brycheiniog.  Four down, four more to go

Our onward route headed south over Fan Hir and proved quite stunning as we cycled down from the summit of Fan Brycheiniog, up the slopes of Fan Hir, over its high point and down its extended southerly ridge.  Except for occasionally stopping to take photographs we cycled this entire route to within a couple of hundred metres of the road where we were met by Barry.

Cycling over Fan Hir was exhilarating

Open and free and all the way down to Glyntawe

We met Barry just north of Glyntawe and stopped off for a welcome drink in the local pub, before cycling the four miles up the A 4067.  At the top of this road we found a quiet spot to have a late lunch before heading east on a minor road toward Heol Senni.  This minor road skirts the northern flank of the Fforest Fawr hills and reaches its high point at around 420m, it then plunges down to Heal Senni loosing almost 180m in height as it does so.  Much of this section is on open land and has sheep wandering from their hillside grazing onto and over the minor road to find juicy morsels of grass on the opposing grass verge.  This section of road is almost 2km in length and has no significant corners on it, with much of it being completely straight, we both put our heads down and our backsides over the back of the seat and hurtled down the road with Mark overtaking a car and me almost wiping out a sheep, having reached 52mph we pulled on the brakes as we entered Heol Senni, this would prove the fastest time recorded during the ten day expedition.

Arranging to meet the back-up vehicle at the Storey Arms at the top of the A 470 we continued out of Heol Senni and onto a short section of the A 4215 before turning right onto a minor road that took us to the busy A road.  This road is the major north – south trunk road in Wales and thankfully we were only cycling on it for about 3 miles.  Our fitness levels were now attuned to the rigours of each day and we set a good pace cycling up the road, it was good to see Hazel and Barry pulled up off the road opposite the Storey Arms and we rested for a few minutes happy in the knowledge that our next hill; Fan Fawr, was straight above us and could be tackled in the evening.

As Hazel and Barry drove down the road to a large lay-by next to forestry which would be our camp for the night, Mark and I sped up Fan Fawr.  It took us 30 minutes to get to the top from the Storey Arms, we only stopped once and I quickly took a photo for posterity as we did so.

On our way up Fan Fawr

The view from the top was stunning with beautiful evening summer light, and Mark stood next to the small summit cairn with his bike raised above his head.  We spent a number of minutes on the summit soaking in the view, another hill had been completed and it had only taken us 30 minutes to do so! 

At the summit of Fan Fawr.  Five down, three more to go

Just before setting off on our 12 minute ride down Fan Fawr

Looking out from the summit of Fforest Fawr the days seemed to be merging into one another with Fan Brycheiniog and Fan Fawr visited today, Pen y Fan planned for tomorrow and Drygarn Fawr visited yesterday, we were making excellent progress and celebrated by whizzing down from the summit of Fan Fawr back to the Storey Arms in 12 minutes.

After cycling down the road we joined Barry and Hazel in the back-up vehicle as the local midges plagued us, they really were quite evil during the night.  Tomorrow we were heading up to Pen y Fan, the highest summit in the Brecon Beacons and also the highest point that we would reach during our ten day adventure.

Tomorrow:  Brecon Beacons – Crickhowell – below the Black Mountains     

Mapping Mountains – Trimble Surveys – Y Mynydd Du

14.04.14  Bwa'r Llyn (SN 798 214), Picws Du (SN 811 218), Fan Brycheiniog (SN 824 220) and Fan Hir (SN 830 209)

Fan Brycheiniog (SN 824 220) and Picws Du (SN 811 218)

What stunning hills we visited today!  I first ventured south to the delights of Y Mynydd Du in July 1989; I’ve visited many times since, but not to the higher hills since March 2003.  I’ve rather neglected the beauty of these hills over the last few years.

It was another celebratory day as it was Ed’s first hill walk since taking early retirement.  We discussed the possibilities yesterday with a number of hills mentioned, but with a forecast of fine weather we decided upon a two hour drive south to the tranquil realms of the south Wales old red sandstone giants.

There is now a gravelled car park at the end of the track at SN 799 238, from here we walked up the continuation of the track as it makes its way toward a small fish farm marked as Filter Beds on the OS 1:25,000 map.  There was a slight chill in the breeze and the forecast blue skies had not yet materialised.  But these soon developed as we joined the path that leaves the track and heads west above Llyn y Fan Fach.

The first hill we visited was Bwa'r Llyn at SN 798 214 which is named in the Nuttalls list as Waun Lefrith.  This was one of the new entries to their list of Welsh 2,000ft mountains as it was surveyed using a basic levelling technique and found to have the required 15m of rise to enter the list.

The path up to this summit is a good gradient and gives ever expansive views down on to the lake and the sublime beauty of the sandstone cliffs.  Usually etched in their greens and reds when the sun is out, with darkened shadows accentuating their rippled effect; this view never disappoints.

We passed many large hessian bags full of gravel for path repairs; it wasn’t the only repair to the path we came across during the days walk.  We rested at the summit after testing our powers of observation with trying to determine which blade of grass is the highest; we then rested at the bwlch with two quad bikes appearing over the horizon with local farmers driving the sheep on to more fertile pasture.

The last uphill toward the first summit of the day, past sacks of gravel, presumably for use in path repair

Ed beside the summit cairn on top of Bwa'r Llyn

Sheep gathering on Y Mynydd Du

The continuation on the escarpment edge from here toward the remaining summits of the day is one of my favourite stretches of hill country in the whole of Wales as the going underfoot is good and views even better.  To our left the ground plunged downward toward the expanse of Llyn y Fan Fach with the great cirque of cliff framing the lake.

Looking back toward our inward route with Llyn y Fan Fach nestling below

The second summit of the day was Picws Du which is part of the collective Bannau Sir Gaer.  We both had a good look at the cairn as we tried to establish the highest point.  The ground below the central rocks seemed the highest, but it is probably made up of the detritus of the cairn so I opted for a small embedded rock beside the cairn and gathered 11 minutes of data.

The Trimble GeoXH 6000 gathering data at the summit of Picws Du

One or two people visited the summit as the Trimble gathered data, including the remarkable Brian Cooper, who was on a 20 mile wander around the hills, having done 26 miles yesterday and 24 miles the previous day, and no doubt more tomorrow.

The remarkable Brian Cooper who walks 4,500 miles per year and said 'The longest spell without a good walk I've had since 2006 is three days, and that was when my wife died, for her funeral'.

By now the sun was out and shone brightly down upon a land of bleached hill grass, not yet luxuriantly green.  The eastward route down to Bwlch Blaen Twrch passed a number of staked out hurdles, all running parallel down the hillside toward the bwlch.  All regimentally put in place to discourage walkers from using the slightly eroded path.  I suppose erosion management is an important factor is such a fragile environment, but we both thought the wooden barricades to be a little over the top.

Keep off the path!

More data was collected at the bwlch before we contoured around the south-western bulk of Fan Brycheiniog, the going was pathless and a little rough in places, but not uncomfortably so.  Our next stop was at Bwlch Giedd, the connecting bwlch between this ranges high point and that of Fan Hir.  By now Ed was well and truly in relaxing mode and as the Trimble gathered its data he flopped out in the sun.

Picws Du (SN 811 218)

The same happened on the summit of Fan Hir, this proved relatively easy to identify, and as another ten minutes of data was collected Ed took full advantage and lay out on the summit soaking up the sun and the prospect of stress free life outside the confines of the work ethic.

Fan Hir (SN 830 209)

We retraced our steps to Bwlch Giedd and continued north-west up to the high point of the day, not the summit that I’d visited many times before, which is the land beside the trig pillar at SN 825 217, but the relatively newly crowned high point of Y Mynydd Du, which is at Tŵr y Fan Foel at SN 824 220.  The high point was established by using a level and staff in 2011 by the DoBIH team whilst on their first annual meet.  The trig position and that of Tŵr y Fan Foel are both given the height of 802m on Ordnance Survey maps.

Looking toward the trig atop Fan Brycheiniog with the hill's high point; Tŵr y Fan Foel, in the background

The Trimble was placed on the highest bit of grass beside the summit cairn and as 12 minutes of data was gathered we relaxed and looked at the map.  We had a couple of options for our descent and decided on the northern route directly down from the 781m Fan Foel at SN 821 223.

The Trimble GeoXH 6000 gathering data at Tŵr y Fan Foel

Tŵr y Fan Foel (SN 824 220)

As height was lost we picked up sheep paths amongst the land that led down toward the car.  During the last few minutes we could look to our left at the majestic sweep of Y Mynydd Du, a truly wonderful place.


For those contemplating early retirement I think Ed can recommend it:

Survey Result:

Bwa'r Llyn (significant name change)

Summit Height:  676.2m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 79820 21451 (Trimble GeoXH 6000)

Bwlch Height:  660.2m (LIDAR)

Bwlch Grid Reference:  SN 80083 21357 (LIDAR)

Drop:  16.1m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  2.37%




Picws Du

Summit Height:  749.1m (converted to OSGM15)

Summit Grid Reference:  SN 81171 21858

Bwlch Height:  655.9m (converted to OSGM15)

Bwlch Grid Reference:  SN 81635 21728

Drop:  93.2m (Subhump status confirmed)

Dominance:  12.44%

Fan Hir

Summit Height:  760.0m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 83090 20921 (Trimble GeoXH 6000)

Bwlch Height:  717.0m (LIDAR)

Bwlch Grid Reference:  SN 82898 21275 (LIDAR)

Drop:  43.0m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  5.66% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Fan Brycheiniog

Summit Height:  802.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 82435 22060 (Trimble GeoXH 6000)

Bwlch Height:  378.5m (LIDAR)

Bwlch Grid Reference:  SN 87056 19547 (LIDAR)

Drop:  424.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  52.84% (Trimble GeoXH 6000 summit and LIDAR bwlch)

For details on the bwlch survey of Fan Brycheinig

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