Mapping Mountains – Trimble Surveys – Banc Llechwedd Mawr

 

09.07.22  Disgwylfa Fawr (SN 737 847) and Disgwylfa Fach (SN 736 838) 

Disgwylfa Fawr (SN 737 847)

As the forecast gave for particularly warm conditions from late morning on, we had a relatively early start having driven down the track leading to Llyn Syfydrin.  This lake is positioned in the heartland of the Pumlumon range and gives easy access to Disgwylfa Fawr and its adjacent hills.  We planned on visiting two hills on this first walk of the day.  However, there are a number of P30s in this area, many of which can be combined during extended walks via connecting tracks through quiet, almost forgotten land. 

Llyn Syfydrin

Intermittent cloud gave some respite from the sun as we left the car and made our way on the track leading toward the old building of Syfydrin.  Before reaching this we branched leftward on another track; unmarked on my map, which steadily gained height before levelling off.  This approach headed direct toward the western flank of Disgylfa Fawr, a hill I had only visited once before in March 2003, when along with Eryl and Stephen we visited six hills during a 5 hour 15 minute walk starting from the western shore of the Dinas Reservoir.  On this first visit this land left me with an impression of openness and wildness, with bleached moor and remains of old farm houses adding a feeling of abandoned tranquillity. 

Aled heading up the steep slopes of Disgwylfa Fawr

Nowadays earthen tracks indicating the off road use of trail bikes gauge part of this land and two of these tracks led steeply up the western flank of Disgwylfa Fawr.  I put my head down and ever so slowly started on the steep uphill plod, whilst Aled wisely took a route contouring up and waited for me at the top of the steep section.  Occasionally I rested, turned and looked down toward the lake and the continuation of land as it headed westward toward the sea, which this morning crested the horizon, temptingly blue with its straight lined edge piecing the point between sea and sky. 

Taking a rest whilst on the steep section

Once over the steepest section I followed Aled as he headed toward the summit of the hill, which is crowned with a small cairn.  The views from this vantage point are extensive and whilst I set the Trimble up to gather data, Aled sat looking north out toward the expanse of Nant y Moch Reservoir and a multitude of hills that radiated out in all directions. 

LIDAR summit image of Disgwylfa Fawr

Prior to visiting these hills Aled had analysed them via available LIDAR which only covers the higher of the two.  With the summit now being Trimbled the LIDAR would at least give an accurate height and position for the bwlch of Disgwylfa Fawr. 

LIDAR bwlch image of Disgwylfa Fawr

As the Trimble slowly beeped away gathering its individual datum points, I sat beside Aled whilst a slight breeze blew across the upper hill.  When data are collected gives time for my body to rest, with my mind taking over with conversation and view to enjoy.  All too soon though, the Trimble had gathered its allotted data and once switched off and photographs taken we headed down the southern slopes toward our second hill of the day; Disgwylfa Fach. 

The inward route from Llyn Syfydrin

Aled at the summit of Disgwylfa Fawr

Gathering data at the summit of Disgwylfa Fawr

Between Disgwylfa Fawr and Disgwylfa Fach is the critical bwlch for the latter, smaller heighted hill.  A fence followed the course of the bwlch in the valley to valley direction.  Either side of the fence was a mass of high reed grass, indicating bog.  We had encountered slithers of peaty wetness on the lower part of our walk down to this bwlch and even though it was high summer the ground was still wet.  In winter this would probably be a quagmire.  We debated where the critical point of the bwlch was positioned and decided it roughly followed the course of the fence and therefore I placed the Trimble on a convenient fence post, took a measurement offset between its internal antenna and the ground at its base and as Aled made his way through almost waist high reed grass to the relative comfort of the grassland beyond, I set the equipment to gather data. 

Heading toward Disgwylfa Fach

Crossing the bwlch

As the Trimble gathered its allotted data I initially lay on the reed grass below the equipment, but my shorts soon got wet and therefore I spent five minutes or so kneeling on tussocks of reed grass endeavouring to remain as dry as I could. 

My view during the bwlch survey

Gathering data at the bwlch of Disgwylfa Fach

It proved a slow plod up to the summit of Disgwylfa Fach.  At this time of year great swathes of the Pumlumon hills are covered in thick grassland, which can be torturous to walk through.  The route from bwlch to summit was not great in distance but was pathless, first through the reed grass at the bwlch followed by thick grass on the upper slopes.  It was heavy going and especially as the sun was increasing in strength and the temperature was ebbing ever upward. 

Gathering data at the summit of Disgwylfa Fach

As the Trimble gathered data from the summit of Disgwylfa Fach I again joined Aled and sat, relaxed and enjoyed the view.  Moments like this are to be savoured as all too soon the five minutes usually allocated for data collection are over and it is time to pack the equipment away and head off. 

The grasslands of the Pumlumon hills

We now had to reclaim lost height to crest the broad south-western ridge of Disgwylfa Fawr.  This was relatively easy with sheep paths followed leading us back to our inward track above the old building of Syfydrin.  By the time we arrived back at the car the temperature had rocketed.  But there were still two more walks to do, both relatively small in length, with just one for me whilst Aled planned on doing the both. 

Almost back at the car

Leaving Llyn Syfydrin I drove up the track to the narrow paved road and followed this southward toward Ponterwyd and then connected with another narrow road heading north toward Nant y Moch Reservoir, which in time led us toward our next track leading toward Banc yr Ŵyn (SN 741 902); which for me would be my last hill of a very hot day. 

 

Survey Result 

 

Disgwylfa Fawr

Summit Height:  506.1m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 73729 84737 (Trimble GeoXH 6000)

Bwlch Height:  352.5m (LIDAR)

Bwlch Grid Reference:  SN 73605 86685 (LIDAR)

Drop:  153.6m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  30.35% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

 

Disgwylfa Fach

Summit Height:  414.2m (converted to OSGM15)

Summit Grid Reference:  SN 73653 83882

Bwlch Height:  375.4m (converted to OSGM15)

Bwlch Grid Reference:  SN 73652 84116

Drop:  38.8m

Dominance:  9.36%

 

 

For further details please consult the Trimble Survey Spreadsheet