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}