Mapping Mountains – Trimble Surveys – Foel Cedig

 

25.02.22  Moel Heulog (SH 987 353) 

Moel Heulog (SH 987 353)

With the late winter storms receding and a forecast for a dry and partly sunny day, I took the opportunity and visited Moel Heulog, which is an unassuming hill rising beside the B4391 road as it crosses the Y Berwyn from Llangynog to Y Bala.  This hill is one of three potential P30s that I had noted during recent map study and LIDAR analysis and over the next few months I hoped to survey each in turn. 

Moel Heulog is given a 376m summit spot height on the contemporary Ordnance Survey 1:25,000 Explorer map; with interpolation of bwlch contouring giving this hill an estimated c 28m of drop.  However, the old Interactive Coverage Map that was hosted on the Geograph website had a 346m bwlch spot height positioned at SH 98935 35205, resulting in 30m of drop.  Therefore, this hill was reclassified to Trichant status due to the bwlch spot height, but with contouring suggesting otherwise it was prioritised for a Trimble GeoXH 6000 survey. 

Getting to the hill proved problematic as the upper part of the B4391 road was closed due to resurfacing.  This meant a long detour via Llanwddyn, Llyn Efyrnwy and the Hirnant pass before re-connecting with the B4391 road and then heading back up the Y Berwyn but this time in the opposite direction to the one planned.  Even this was a risk as I did not know how much of the upper section of the road was closed.  Thankfully Moel Heulog is positioned on the western end of this mountain road and it was the easterly section undergoing resurfacing.  After finding my designated parking spot I gathered all necessary equipment and headed over a small foot stile on to a soggy field which gave access toward the bwlch and then summit of this hill. 

A public footpath crossed the field heading toward a gate which gives access to the narrow lane on the eastern side of the hill; this lane also crosses the connecting bwlch.  All was relatively quiet as I made my way over the field, with an occasional rogue car still heading over the Y Berwyn on the closed road and a tractor slowly chugging its way on the narrow lane.  A drainage channel across the field meant that wellies; my preferred footwear for this time of year, proved a good chose with water flowing down the channel and muddied and slippery sides.  Beyond the drainage channel the field led up to the gate and lane at the bwlch. 

Having spent a few minutes assessing the lay of land beside the lane I positioned my rucksack and the Trimble atop it where I judged the critical point of the bwlch to be positioned.  I then measured the offset between the equipment’s internal antenna and the ground at its base and waited for the 0.1m accuracy level to be attained before data should be logged.  During the waiting process two cars approached from the north, I flagged each down in turn and explained what I was doing and asked them to be careful when driving past the equipment, they duly were and soon the Trimble was activated to gather its allocated data. 

Gathering data at the bwlch of Moel Heulog with the southerly top in the background

Having collected five minutes of bwlch data I approached the Trimble to close it down just as a tractor rounded the corner from the south.  It stopped and I chatted with the farmer for a few minutes before waving him off and packing the equipment away. 

This was my first survey for quite a while and it felt good to be back on the hill, albeit I had so far only been waiting on a country lane whilst the Trimble did its stuff.  However, many similar surveys have taken place over the last eight years and the waiting process has an unusual therapeutic element to it, and one that I am now accustomed to. 

The Trimble GeoXH 6000 set-up position at the bwlch of Moel Heulog

The map shows this hill with two tops, one metre apart in height, with the southerly the lower with a spot height of 375m.  It was this southerly top that I approached first and as I was now standing on its high point I decided to gather data from it.  As the Trimble quietly beeped away gathering its individual datum points I looked west toward the impressive bulk of Arenig Fawr standing out whitened with snow, with Mynydd Nodol to its right looking relatively small in comparison, it was this latter hill that was next on the day’s surveying agenda. 

The southerly top from the approach across the field

Arenig Fawr from the southerly summit of Moel Heulog

After packing the equipment away I headed over an intervening fence to the higher northerly summit where I was met by two friendly horses, both nuzzled toward me as I set the Trimble up.  One remained beside me as I measured the offset; they only sauntered off as I checked on the positioning of the equipment before activating it to gather data.  During data collection the horses thankfully kept their distance. 

An extremely friendly horse

It felt good to be on the summit, with horses and sheep as companions, blue sky and a slight chilled breeze as accompaniment, and waiting for the world to pass me by.  Such times are now the expected norm, and the experience seldom disappoints.  They afford a time to ponder, with thoughts aplenty or to drift where one’s mind wanders. 

Gathering data at the summit of Moel Heulog

As I left the summit using two gates for access down to the field and drainage channel below, I looked across to where the two horses now were, bade my farewells and wandered back toward my awaiting car.  The survey had been salvaged with the re-routing due to the road closure giving the prospect of not being able to get to the hill.  The survey also gave opportunity to get my mind-set back on hills and surveying after a long self-imposed winter break.  It felt good to be back. 

 

Survey Result:

 

Moel Heulog

Summit Height:  377.8m (converted to OSGM15)

Summit Grid Reference:  SH 98750 35398

Bwlch Height:  347.0m (converted to OSGM15)

Bwlch Grid Reference:  SH 98941 35209

Drop:  30.7m (Sub-Trichant reclassified to Trichant)

Dominance:  8.14%

 

 

For further details please consult the Trimble Survey Spreadsheet