Wednesday, 24 June 2015

Mapping Mountains – Trimble Surveys – Moel Hebog


15.06.15  Carreg yr Eryr (SH 526 378) and Graig Ddu (SH 522 376)   

Carreg yr Eryr (SH 526 378) on left and Graig Ddu (SH 522 376) on right

With the weather set fine and the prospect of a meal at Dylan’s in Cricieth at 7.15pm to celebrate the coming of age of Alun who turned a frighteningly 60 today, I planned a few little walks around small hills that I had not visited before, all around the Cricieth area, and all marginal P30s.

The first hill of the hill was Carreg yr Eryr which overlooks Black Rock Sands on the outskirts of Morfa Bychan.  I parked in a pull in spot on the way to where this hill’s critical bwlch is situated.

As I got my boots on the warmth of the day had not yet broken through the morning cloud but conditions for a few hours surveying on small hills was ideal.  I walked up the road to where the hill’s critical bwlch lay, this is on a corner of a narrow lane and where a track continues to a few houses.  I had inspected this bwlch in a Google Car the previous evening and wondered how safe it would be to position the Trimble on, or next to the road.

Thankfully I judged the position of the bwlch to be just off the road and on part of the track, however this was directly under a high hedge and adjacent to a number of wheely bins that were awaiting their morning collection.

After waiting a number of minutes for the accuracy of the Trimble to attain its 0.1m level before data can be logged, I wondered about using one of the wheely bins as an improvised tripod, I had also had to guard the Trimble from three cars that passed, one up the lane, one down the lane and one aiming straight for the Trimble approaching from the houses down the track.  The driver of the latter was very obliging and drove a safe distance from the Trimble when I pointed toward it and indicated for him to take a wide berth around it, he duly obliged.

Gathering data at the critical bwlch of Carreg yr Eryr

It took an age for the Trimble to reach the 0.1m accuracy, but when it did I pressed ‘Log’ and picked it up after five minutes of data collection, packed it away and started walking up another lane which gives access toward the top of Carreg yr Eryr.  A few seconds later and the bin lorry pulled up directly on the spot where the Trimble had been placed, the wheely bins were be collected and the Trimble had got its five minutes of data with no more than 30 seconds between it being picked up and ending up in the back of, or under a large bin lorry.

The lane led to the bwlch between Carreg yr Eryr and Graig Ddu, the former has a 53m spot height on Ordnance Survey maps and the latter an uppermost c 50m contour ring, so I wanted to survey both.  Graig Ddu also has another small c 50m contour ring on its summit area, but this was visually dismissed as being lower than its main summit when I arrived at its top.

Moel y Gest dominating the grassed summit of Carreg yr Eryr

I set the Trimble up on the high point of Graig Ddu and stood back as it gathered data and admired the view with Castell Cricieth away to west, this would be my last surveying objective of the day and I hoped the castell would remain a P30 as it has only recently been discovered by Alex Cameron.

Castell Cricieth would be my last hill and survey of the day

It was lovely to be on the edge of land overlooking the sweep of sea, there always seems to be a special beauty to seascapes, one that is hard to define, but their ending of land and flatness of sea is sometimes other worldly and pleasantly appetising.

Gathering data from the summit of Graig Ddu

Once the summit data were gathered I backtracked down to the lane and accessed the summit of Carreg yr Eryr through a gate and a field.  The high point proved to be at the top of a rock outcrop and soon the Trimble was collecting data from its top.

The great sweep of Black Rock Sands

As the Trimble gathered its data the warmth of the morning’s sun broke through the cloud and warmed up proceedings.  I was soon back on the lane heading down toward the bwlch admiring a newly cropped flock of sheep on the way.

Gathering data from the summit of Carreg yr Eryr

Newly cropped and out in the sun

Both summits proved enjoyable little ventures with that of Carreg yr Eryr seemingly higher when viewed visually, but Graig Ddu is certainly the more appealing as it sits wind-blown and open to the westerly sea elements.  Next stop Moel y Gadair and an encounter with a Carp lake.


Survey Result:


Carreg yr Eryr

Summit Height:  53.3m (converted to OSGM15)

Summit Grid Reference:  SH 52627 37813

Bwlch Height:  22.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 52976 37896

Drop:  30.9m (30-99m Sub-Twmpau reclassified to 30-99m Twmpau)

Dominance:  58.06%




Graig Ddu

Summit Height:  52.9m (converted to OSGM15)

Summit Grid Reference:  SH 52259 37621

Drop:  c 19m

Dominance:  35.94%



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




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