Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

16.01.16  Trwyn y Fuwch (SH 813 823) and Creigiau Rhiwledyn (SH 814 825)

Trwyn y Fuwch (SH 813 823)

Driving through the outskirts of Mold I looked back toward the south-east and the high splattering of cloud was ablaze with every hue of pink imaginable; hopefully the star encrusted sky that had now evolved in to this gentle and rather beautiful sunrise foretold a good day on the hill.  I was heading to Colwyn Bay to meet Alex as I’d asked him if he would be my guide for the day on a number of local P30s.  Each planned hill had been picked with the intention of getting a selection of reasonable photographs to include in Y Trechol – The Dominant Hills of Wales.  This list is being put in Group format bi-weekly on the Mapping Mountains site and the first group that I had no photograph for is that of Moelfre Uchaf, and the hills around Colwyn Bay formed part of this Group.

By the time I’d arrived at Alex’s the clear conditions to the east had been replaced by a high blanket of grey cloud in the west, this was a disappointment as the weather forecast predicted a dry day in Wales with lots of sunshine.  Alex finished sorting his stuff out including bringing a stove which proved one of the highlights of the day, and away we went with Alex directing me toward the top of the B5115 where parking can be found adjacent to a Premier Inn at SH 811 821.

Our first P30 was Trwyn y Fuwch, otherwise known as the Little Orme, this is one of two headlands either side of Llandudno Bay, with the other being Gogarth (Great Orme).  A kissing gate gives access to the well-worn footpath leading up this hill’s southern ridge; a left branch from this path took us up a small rock band on to the higher exposed limestone that predominate these hills.  As Alex led the way I looked past the great sweep of the bay toward Gogarth, which if not for the concrete and steel metropolis of Llandudno would no doubt, in time, become its own island, adrift from the mainland as the sea imperceptibly cut through the low lying land barrier between it and the Conwy Sands.

Alex heading toward the summit of Trwyn y Fuwch

We soon arrived at the summit which is adorned with a brightly white trig pillar, relatively newly painted; it looked slick and cared for, and had, with one or two other local trigs, been painted by Alex.  The high point of the hill is positioned approximately 14 metres from the base of the trig and consists of closely cropped grass.  As I set the Trimble to gather data, we both stood below it and looked toward this hill’s north-eastern top; Creigiau Rhiwledyn, which Alex suggested could be Trimbled.

Gathering data at the summit of Trwyn y Fuwch

Once five minutes of data were collected I packed the Trimble away and we headed down to the connecting bwlch where I placed the Trimble on top of my rucksack to give it elevation above the surrounding ground, this improvised form of surveying works extremely well and in essence creates a makeshift tripod for the Trimble, all one has to do is remember to measure the offset between the ground at the bae of the rucksack and the position of the internal antenna within the Trimble.

Gathering data at the bwlch area of Creigiau Rhiwledyn

Beyond the bwlch lay the summit of Creigiau Rhiwledyn which has no height given it on any map that I have seen.  One of the delights of surveying is giving such points an accurate height, this hill, with its northern cliffs plunging straight down to the sea stood a chance of being elevated to the ranks of Sub-Twmpau, so for me, the survey was a worthwhile one, and it would also be good to give the two tops a height difference when compared to one another.

Visiting the second top also gave us views back toward the summit of Trwyn y Fuwch and as one of the priorities of the day was photography I hoped that I would have at least one good photo of this Dominant Hill.

The high point of Creigiau Rhiwledyn proved to be a small embedded rock about 1.5 metres from the base of the summit cairn, having set the Trimble up to gather data we walked further north-east to look down toward the path that heads up this hill from the coast, Alex had already recommended this route and the small part of it that could be seen from this vantage point looked appealing.

Gathering data at the summit of Creigiau Rhiwledyn

By now a few specks of rain were falling, this wasn’t a surprise as the sky was slate grey and looking ominous, the forecast for this part of the country was obviously wrong and the rain band predicted to reach the north of Ireland, south-west Scotland and Cumbria looked as if it had edged its way further south-east.

Once another five minutes of data were collected I packed the Trimble away and we headed down a path that re-joined our inward route half way down the hill.  Next stop Mynydd Pant (SH 810 816).    

LIDAR image of Creigiau Rhiwledyn (SH 814 825)

Postscript: 

Since the survey of these hills full LIDAR coverage is now available.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height and positional data that is now freely available for England and Wales.  Consequently the numerical details for these hills have been analysed using this technique, resulting in the LIDAR height and position for the bwlch of Creigiau Rhiwledyn being prioritised in preference to that produced by the Trimble GeoXH 6000.

Survey Result:

Trwyn y Fuwch (significant name change)

Summit Height:  141.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 81314 82382 (Trimble GeoXH 6000)

Bwlch Height:  6.3m (LIDAR)

Bwlch Grid Reference:  SH 78249 82533 (LIDAR)

Drop:  135.4m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  95.56% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Creigiau Rhiwledyn

Summit Height:  136.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 81450 82503 (Trimble GeoXH 6000)

Bwlch Height:  117.3m (LIDAR)

Bwlch Grid Reference:  SH 81382 82471 (LIDAR)

Drop:  19.5m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  14.26% (Trimble GeoXH 6000 summit and LIDAR bwlch)

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