Mapping Mountains – Trimble Surveys – Elenydd

15.10.20  Cae Pen y Maen (SN 656 694) 

LIDR image of Cae Pen y Maen (SN 656 694)

Cae Pen y Maen used to be listed as a 200m Twmpau and also a Subhump, with the latter list previously giving the hill 95m of drop, based on a 297m summit and 202m bwlch height.  Its P30 and Subhump status was subsequently relocated to its adjacent hill, which is listed as Banc y Maen Rochorlem (SN 675 691) in the 200m Twmpau list.  Its relocation was due to a 299m summit spot height that appeared on the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive coverage Map. 

Just over two weeks ago I’d visited the summit of Banc y Maen Rochorlem and surveyed it, and even though Cae Pen y Maen was relatively close the lack of time and daylight hours meant that I bi-passed it.  Today the opportunity to visit and survey this summit could not be missed and it had been pencilled in as one of nine hills to visit during the day with Charles Everett. 

By the time we parked just below the summit late afternoon light was casting long shadows on the narrow lane leading up toward the gate that gives access to the uppermost field of the hill.  This hill was the penultimate one of our mini-bagging bonanza and as with many others; it proved a delight to visit. 

Heading up the lane toward the gate to access the summit field

As Charles sat on the small plinth at the base of the trig pillar which is placed about 100 metres from the summit of the hill, I used the Trimble as a hand-held device to zero in on the ten figure grid reference that LIDAR analysis gives for the summit. 

The Trimble was soon set up gathering data, and I then stood back writing all necessary details in my note book.  During data collection a number of cows slowly crept toward the equipment, from the vantage point of the trig pillar Charles shouted over that they were still below it, therefore not interfering with satellite reception, which reassured me. 

The Trimble set-up position at the summit of Cae Pen y Maen

Once the allotted data were gathered and stored I closed the equipment down, packed it away and joined Charles by the trig.  A few minutes later we were back at the car, it had taken 25 minutes to visit and survey the hill; however I now wanted to get to grips with its connecting bwlch which looked as if it was positioned in a large bog. 

Even though I encouraged Charles to join me in the bwlch bog survey he politely and very wisely declined.  The bwlch of Cae Pen y Maen is positioned a short distance on the continuation of the narrow lane from where we had parked for the summit.  A few minutes later and I was parked beside the bwlch, it looked rather daunting and uninviting.  Thankfully I had brought my wellies. 

The bwlch of Cae Pen y Maen

Leaving Charles to relax in the car I headed off to its watery realm, firstly following a fence line adjacent to the bog which gave a semblance of dry ground and then I went for it.  The bog consisted of a multitude of tussocks and the further I ventured in to it, not surprisingly the more watery it became. 

I’d come with a ten figure grid reference for its interpolated position from the old 5m contouring on the OS Maps website.  It took me an inordinate amount of time to stumble through the tussocks zeroing in to this position, but eventually I arrived at it. 

Late afternoon light on an old ruined farm house

By the time I set the Trimble up to gather its allotted data the sun was low in the sky giving beautiful colour that illuminated the reed grass at the bwlch.  The wellies had proved a necessity and as the Trimble quietly beeped away I stood back and wondered how many people had ventured in to this place of bog and methane gas which rose as I stumbled my way through its tussocky depths. 

Gathering data at the bwlch of Cae Pen y Maen

Once I packed the Trimble away I had options to get out of the bog, I could retrace my inward route, or head over the bog to a gate and relatively safer ground on its other side, or head straight for the car, which looked back at me like a tempting beacon.  I chose the latter and proceeded to wade through all manner of unsavoury undergrowth. 

During data collection a large van pulled up beside my car and when I emerged out of the bog it proved to be the local farmer, who was wondering with an inquisitive smile on his face what on earth someone was doing immersed in his bog.  Charles had already explained that we were eccentrics and I added an in depth explanation of the Trimble and how critical a critical bwlch actually is, and a few moments later Charles and I were away heading for our last hill of the day. 

 

Survey Result: 

 

Cae Pen y Maen (significant name change)  

Summit Height:  296.6m (converted to OSGM15)

Summit Grid Reference:  SN 65690 69496 

Bwlch Height:  268.8m (converted to OSGM15)

Bwlch Grid Reference:  SN 66401 68910

Drop:  27.9m (200m Twmpau reclassified to 200m Sub-Twmpau)

Dominance:  9.40%

 

 

For further details please consult the Trimble Survey Spreadsheet