Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

18.09.19  Moel Fechan (SH 993 632, only bwlch surveyed)

This was the fourth of nine planned roadside bwlch surveys during the day and each had either been LIDARed, examined in detail via 5m contouring on the OS Maps website or driven to and over in a digitised Google car assessing the lay of land and the ups and downs of the hill to hill and valley to valley traverses.

The bwlch of Moel Fechan

As LIDAR does not cover the area of this hill’s summit or connecting bwlch I was reliant upon map contours and the Google car for pre-visit assessment, and then an on-site inspection when there.

The ‘there’ part was a grass verge beside the A543 road close to a cross roads intersecting with the B5435 and a minor road.  I’d already found a parking place via driving the Google car and was soon loading up with all necessary equipment including my newly purchased surveying steps which are ideal for car roof surveys as they give height to see the screen to create the file necessary to start gathering data.  They are also ideal for grass verge roadside surveying as they give the Trimble an added semblance of protection when balanced on top of my rucksack and importantly a higher position which enhances satellite reception.

The set-up position at the bwlch of Moel Fechan

As I approached the cross roads and turned right on the B5435 to park in a pull in place close to a gate, a tractor with attached hedge cutting equipment was parked nearby.  Leaving my car I walked the short distance up the A543 to where I judged the critical point of the bwlch to be positioned.  As I did so the tractor started chugging up the road conveniently cutting the grass verge where I was just about to set the equipment up.  I flagged the tractor down and quickly explained what I wanted to do, the driver said he wouldn’t be heading back up the road for 15 minutes or so, which was all I needed, and once the grass was cropped I unfolded the surveying steps and positioned my rucksack on top with the Trimble placed atop the latter; giving a measurement offset of 0.95m between its internal antenna and the ground below.

Gathering data at the bwlch of Moel Fechan

A few vehicles zoomed past as the Trimble beeped away gathering data.  During data gathering I stood beside the road 50 metres or so from the equipment and waited for the allotted data to be gathered and stored.

I left the Trimble gathering data for six minutes and then closed it down happy in the knowledge that another bwlch survey was complete.  All that remained was to pack the Trimble away, fold the steps up and walk the short distance back to my car.  Next stop the bwlch connecting to Foel Gasyth.

Survey Result:

Moel Fechan

Summit Height:  372m (spot height)

Summit Grid Reference:  SH 99335 63247 (hand-held GPS via DoBIH)

Bwlch Height:  299.2m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 98493 63393 (Trimble GeoXH 6000)

Drop:  73m (spot height summit and Trimble GeoXH 6000 bwlch)

Dominance:  19.56% (spot height summit and Trimble GeoXH 6000 bwlch)

  

For further details please consult the Trimble Survey Spreadsheet