Mapping Mountains – Trimble Surveys – Hirddywel

12.03.16  Pen Crwn (SN 963 736), Cefn Penlan (SN 952 755), Drysgol (SN 946 744), Bryn Titli (SN 933 757), Garreg y Noddfa (SN 930 761), Garreg Lwyd (SN 942 733), Mynydd Perthi (SN 953 727) and Yr Wylorn (SN 959 724)  

Bryn Titli (SN 933 757)

When contacting people in regard to the Table of Progress for Y Pedwarau I struck up email conversation with a number of people, one being Fergal Hingerty.  Fergal is a native Irishman who now resides in Bristol with many if not all of his weekends spent bagging hills.

Fergal’s hill bagging story is a remarkable one as he was diagnosed with advanced stage one of spinal degeneration which left him with the prospect of life in a wheelchair.  After undergoing a 9½ hour operation and months of rehab he is now walking the hills and is quickly amassing his Pedwar total.  An invite to join him on a walk was not to be missed.

We met just to the north of Rhaeadr Gwy (Rhayader) and parked our cars farther up the minor road that makes its way to St Harmon.  The circuit we had planned was a horseshoe walk around the valley that encloses the Marcheini Fawr stream.

As we ascended a muddy track toward the summit of our first hill of the day; Pen Crwn, the overhead conditions of grey skies with a steak of early morning brightness gave the prospect that the cloud would break and give us welcome sunshine.

Fergal nearing the summit of Pen Crwn

The summit of Pen Crwn comprises moor grass and as the Trimble gathered its customary five minutes of data we stood and chatted and considered the route ahead.  Initially this was following the hill’s broad northern ridge which gave us heathery and boggy conditions until easier grass was found which took us down to the hill’s bwlch.

Gathering data at the summit of Pen Crwn

After surveying the bwlch the first light specks of drizzle closed in on us from the north, although only light the drizzly conditions then stayed with us for the rest of the walk.  After packing the Trimble away we continued to the top of Cefn Penlan which is listed as a Sub-Pedwar with c 24m of drop.  This wasn’t a hill on our planned route but as the conifer plantation at its summit had been felled, it seemed wise to visit its highest point and gather another data set with the Trimble.

As the Trimble gathered data we considered our route toward the summit of Drysgol, between us and it was a morass of tussock grass and bog, we opted for a route straight through the tussocks and aiming for a green track that contours this hill’s northern slopes.  Although the going was rough it was not prolonged and soon we were on the green track and heading toward the high point of Drysgol which is immersed in deep heather.

Gathering data at the summit of Cefn Penlan

As Fergal wanted to visit as many Pedwarau as he could during the day, he decided that as I continued surveying each summit and bylchau on my way to the top of Garreg y Noddfa, he would head north to the summit of Craig Gellidywyll (SN 951 763) on a there and back walk and catch up with me on the continuing track through the wind turbines that predominate the central part of our planned route.  This was estimated to take an hour; therefore we made our way through the continuing tussocks, heather and bog toward a fence junction where I headed north-west and Fergal headed north.  Off he went, leaving me to survey the critical bwlch of Drysgol which I’d wanted to do ever since getting the Trimble.  I’d estimated this hill’s drop as 102ft (31.1m) from a basic levelling survey that I’d conducted of the bwlch on the 13^th May 2005, and ever since I’d always wondered if this hill had sufficient drop to be included in the main Pedwar list.

Gathering data at the summit of Drysgol

The bwlch consists of more tussocks and is placed to the north-west of where a 457m spot height appears on current Ordnance Survey maps.  It’ll be interesting to see if Drysgol retains its Pedwar status, I for one hope it does, as its summit is isolated from the other hills we planned on visiting during the day’s walk and gives good views and is undisturbed by the wind turbines that scatter themselves across the next bit of land I now headed toward.

Gathering data at the bwlch of Drysgol

As I arrived at the high point of Bryn Titli, which is listed as having 19m of drop and therefore only one metre below Sub-Pedwar status, I looked out into the gloom and spotted Fergal as a small black dot on the summit of Craig Gellidywyll.  By the time I’d positioned the Trimble on top of my rucksack to give it elevation above its moorland surrounds he was making his way back from the summit.

The view from Bryn Titli of the heather bound summit of Drysgol

I quickly made my way down to another bog which constitutes the area of the bwlch of Bryn Titli, and stood on tussock grass just above patches of shallow water as the Trimble gathered another five minutes of data.  Next stop; the summit of Garreg y Noddfa, which I’d previously surveyed with John and Graham in February 2009, its high point is on grass on the northern edge of the track that continues its way south between the turbines that are scattered across this part of land.

Gathering data at the summit of Garreg y Noddfa

By the time I’d packed the Trimble away Fergal had appeared and quickly caught up with me, it had been just over an hour since he had headed off to bag Craig Gellidywyll.  The grey conditions were now set for the rest of the afternoon and the light drizzle continued to fall from a dead pan grey sky that had descended over some of the higher 500m peaks to our west.

We now had another six surveys ahead of us, with the first being in another expansive bog and which constitutes the bwlch of Garreg y Noddfa.  Fergal wisely waited on the gravelled track as I stood in my wellies in water waiting for the Trimble to do its stuff.

Another expansive bog, this one is the bwlch of Garreg y Noddfa

Beyond this bwlch lay the highest summit of the day; Garreg Lwyd, which was another hill I’d surveyed with John and Graham in February 2009.  Its high point is on grass next to a few flat stones which constitute the semblance of a tiny cairn.  By now the grey conditions had closed in and rain showers slowly ebbed down surrounding valleys, but it was never wet enough for me to put my Goretex jacket on and I continued in the hope of trying to keep my camera and surveying gear relatively dry.

Fergal at the summit of Garreg Lwyd

Only two hills remained, Mynydd Perthi which is a Sub-Pedwar listed with 26m of drop and the higher Yr Wylorn which is listed as a Pedwar with 56m of drop.  The grassy eastern slopes of Garreg Lwyd took us down to the next connecting bwlch which is the critical one for Yr Wylorn. 

This bwlch has a grassed ditch and small raised embankment crossing it and therefore its critical point proved difficult to judge.  After collecting data we proceeded to the summit of Mynydd Perthi.  As the Trimble gathered data from this summit I stood with my back to the drizzle which was developing into rain and waited patiently for another data set to be stored.  During the day Fergal and I chatted about a number of things and I thanked him for being patient, as it isn’t everyone who would wait in grey drizzly conditions whilst the Trimble recorded all the data sets during the day, he did so without complaint.

Gathering data at the summit of Mynydd Perthi

On our way to the summit of our last hill of the day; Yr Wylorn I quickly set the Trimble up on the connecting bwlch which is the critical one for Mynydd Perthi, and gathered five minutes of data.  The fourteenth and last data set of the day was on the heathery summit of Yr Wylorn and once the equipment was closed down and packed away we headed down toward the bwlch and connected up with a green track that brought us back to my car.

The fourteenth and last data set of the day at the summit of Yr Wylorn

It proved a good day on the hill with Fergal and as I switched my car radio on to listen to the uncomfortable goings on at Twickenham, Fergal zoomed off in pursuit of another Pedwar to add to his growing number.  

  

Postscript:  Since the survey of these hills, the LIDAR (Light Detection & Ranging) technique is now being used to produce accurate height and position for hills.  Therefore, numerical data produced by surveying with the Trimble GeoXH 6000 is being updated.  However, each individual data set is analysed and as data produced by the Trimble GeoXH 6000 is considered more accurate it is this relative to the position produced by LIDAR that is prioritised.

Survey Result:

Pen Crwn (significant name change)

Summit Height:  486.7m (converted to OSGM15)

Summit Grid Reference:  SN 96320 73629

Bwlch Height:  434.7m (converted to OSGM15)

Bwlch Grid Reference:  SN 95566 75036

Drop:  52.0m

Dominance:  10.69%

Cefn Penlan

Summit Height:  481.4m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 95233 75538 (Trimble GeoXH 6000)

Bwlch Height:  458.3m (LIDAR)

Bwlch Grid Reference:  SN 94615 75529 (LIDAR) 

Drop:  23.0m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  4.78% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Drysgol

Summit Height:  483.6m (converted to OSGM15, Trimble GeoXH 6000)  483.7m (converted to OSGM15, Leica GS15)

Summit Grid Reference:  SN 94630 74415 (Trimble GeoXH 6000)  SN 94626 74408 (Leica GS15)

Bwlch Height:  454.4m (converted to OSGM15, Trimble GeoXH 6000)  454.2m (converted to OSGM15, Leica GS15) 

Bwlch Grid Reference:  SN 93870 75665 (Trimble GeoXH 6000)  SN 93909 75668 (Leica GS15)

Drop:  29.2m (Trimble GeoXH 6000)  29.6m (Leica GS15) (Pedwar reclassified to 400m Sub-Pedwar)

Dominance:  6.04% (Trimble GeoXH 6000)  6.11% (Leica GS15)

Bryn Titli

Summit Height:  492.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 93383 75719 (Trimble GeoXH 6000)

Bwlch Height:  472.7m (converted to OSGM15, height relative to Trimble GeoXH 6000)

Bwlch Grid Reference:  SN 93192 76017 (LIDAR)

Drop:  20.0m (Trimble GeoXH 6000 summit and LIDAR with height relative to Trimble GeoXH 6000 bwlch) (400m Sub-Pedwar addition)

Dominance:  4.06% (Trimble GeoXH 6000 summit and LIDAR with height relative to Trimble GeoXH 6000 bwlch)

Garreg y Noddfa (1st significant name change) (2nd significant name change)

Summit Height:  495.4m (converted to OSGM15) (Trimble GeoXH 6000)  495.7m (converted to OSGM15) (Leica 530)

   

Summit Grid Reference:  SN 93032 76171 (Trimble GeoXH 6000)  SN 93038 76169 (Leica 530)

Bwlch Height:  436.7m (LIDAR)

Bwlch Grid Reference:  SN 93730 74216 (LIDAR)

Drop:  59.0m (Leica 530 summit and LIDAR bwlch)

Dominance:  11.89% (Leica 530 summit and LIDAR bwlch)

Garreg Lwyd

Summit Height:  498.1m (converted to OSGM15, Trimble GeoXH 6000)  498.1m (converted to OSGM15, Leica 530)

Summit Grid Reference:  SN 94214 73326

Drop:  205m

Dominance:  41.15%

Mynydd Perthi

Summit Height:  457.0m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 95321 72719 (Trimble GeoXH 6000)

Bwlch Height:  430.4m (LIDAR)

Bwlch Grid Reference:  SN 95575 72582 (LIDAR)

Drop:  26.6m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  5.83% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Yr Wylorn

Summit Height:  473.8m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 95990 72409 (Trimble GeoXH 6000)

Bwlch Height:  418.7m (LIDAR)

Bwlch Grid Reference:  SN 95211 73208 (LIDAR)

Drop:  55.1m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  11.62% (Trimble GeoXH 6000 summit and LIDAR bwlch)

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