Mapping Mountains – Trimble Surveys – Crib Goch

 

05.10.24  Crib Goch (SH 624 551), Pt. 914.6m (SH 623 551), Pt. 901.8m (SH 622 551), Pt. 906.2m (SH 619 551), Pt. 563.0m (SH 638 551) and Carreg Gwalch (SH 642 552) 

The early birds had already gathered at Pen y Pàs, but pure thriftiness, or perhaps self-imposed meanness, had destined my course past them for a lower starting point near the bottom of Bwlch Llanberis.  As I wearily stumbled out of the car, I spotted lights up on the darkened skyline as an even earlier bird traversed along the north ridge of Crib Goch.  This mountain was the primary surveying objective for the day. 

Sunrise.  Photo: Aled Williams

A steep ascent was tempered by scenes of sunrise, with the silhouette of a cloud-capped Moel Siabod beautifully framed by the walls of Y Pàs, its narrow road conspicuously snaking up the valley below.  Periodic rests allowed me to appreciate the ruggedness of these mountains, vast slopes riddled with rock features of various character.  I marvelled at these being the workplaces of the shepherds, the true “mountain men”. 

Base of the north ridge.  Photo: Aled Williams

I had now arrived at the base of the north ridge.  A fair-weather day had been promised but with 30mph wind speeds and these were most definitely present with occasional blusterier spells.  As I ventured onto the start of the arete, I took note of the greasy rocks, not yet dried from the dampening effects of the overnight mists.

The lower arete.  Photo: Aled Williams

Before continuing further I decided to prepare myself for surveying, in case the winds made it difficult to retrieve the various pieces of equipment whilst on the ridge.  The downside of this was that the collection of objects hanging around my neck and stuffed into pockets restricted movement and tended towards imbalance!  I would have to take the traverse carefully and slowly. 

The upper arete.  Photo: Aled Williams

Despite a few uncomfortable blasts from the wind, the ascent of the north ridge went by without incident and I soon found myself at the eastern end of the summit arete, where a few flocks of those early birds were resting having ascended via the east ridge.  I decided that it would be best to go on before them, thus giving me the opportunity to set up the Trimble GeoXH 6000 while they traversed past me, meaning that data collection could then occur without interference from passers-by. 

The summit arete.  Photo: Aled Williams

My memory of the highest point was thankfully incorrect and it proved a relatively sheltered and safe position to spend what would otherwise be a disproportionate amount of time on such an airy summit.  I immediately started to collect 5 minutes of data once the first group of people passed by and was not interrupted by others.  I packed away the equipment happy with the thought that the summit of Crib Goch had now been surveyed. 

Surveying the summit of Crib Goch.  Photo: Aled Williams

The next objective was to survey the bwlch and then the summit of the highest of Crib Goch’s famous pinnacles.  Both points were easily surveyed, with an Abney level being used to locate the highest spike of rock atop the pinnacle. 

A window on the world.  Photo: Aled Williams

As I packed away the equipment atop the highest pinnacle, numerous groups were now making their way along the summit arete.  It was getting busier and this would make surveying the lowest of the pinnacles very difficult. 

The highest of the pinnacles.  Photo: Aled Williams

The problem became apparent once I arrived at the bwlch of the lowest pinnacle.  Its position was a nick between two rocks, exactly at the start of the easiest route that allows passage up and over the pinnacle.  The best approach was to survey it in a time window between the groups of people.  Unfortunately, the tight confines of the bwlch impacted the Trimble’s ability to reach its required accuracy level for measurement.  Just as it was close to reaching this level, a group of people would pass and it would shoot back up to inaccurate levels again! 

The problematic tight bwlch of the lower pinnacle.  Photo: Aled Williams

After a frustrating 45 minutes at the bwlch, data was eventually collected.  I quickly scrambled to the top of the lowest pinnacle and located the highest spike of rock through use of an Abney level.  In contrast, this survey went smoothly and within 10 minutes it had been completed. 

Surveying the summit of the lowest pinnacle.  Photo: Aled Williams

I descended to Bwlch Coch and headed straight to the bwlch of the next top to be surveyed (Pt. 906.2m at SH 619 551).  This was formerly listed as a Welsh Highlands Sub, but was deleted in March 2023 following LIDAR analysis that gave the top only 9.8m of drop.  Given the highly marginal nature of the LIDAR result, this was a priority survey to complete. 

The bwlch of Pt. 906.2m.  Photo: Aled Williams

As the Trimble gathered data, I sat on the grassy edge looking down to Cwmglas Mawr.  The vista of lakes and peaks beyond was stunning, as was the one behind me of Clogwyn y Garnedd and Lliwedd.  A short walk along the narrow ridge of the top brought me to the summit rocks and the Trimble was duly positioned for 5 minutes of measurement. 

Surveying the summit of Pt. 906.2m.  Photo: Aled Williams

After packing up the equipment I headed back to Bwlch Coch, taking the unpleasantly steep descent to Llwybr Pyg during the height of the midday heat.  My final objectives of the day were two Welsh Highland Subs found on the ridge between Bwlch y Moch and Pen y Pàs: Pt. 563.3m and Carreg Gwalch.  These surveys were completed efficiently with not a single walker met along the entire length of the pleasant undulating ridge that joins the two tops together.  All that remained of an excellent day’s surveying was the long plod back to the car.

Pt. 563.0m and Carreg Gwalch.  Photo: Aled Williams.

Survey Result: 

 

Crib Goch

Summit Height:  924.0m (converted to OSGM15, Trimble GeoXH 6000) (average of three surveys)

Summit Grid Reference:  SH 62418 55182 (Trimble GeoXH 6000)

Bwlch Height:  857.2m (LIDAR)

Bwlch Grid Reference:  SH 62168 55116 (LIDAR)

Drop:  66.8m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  7.23% (Trimble GeoXH 6000 summit and LIDAR bwlch)  

 

 

Pt. 914.6m

Summit Height:  914.6m (converted to OSGM15)

Summit Grid Reference:  SH 62309 55153

Bwlch Height:  904.1m (converted to OSGM15)

Bwlch Grid Reference:  SH 62336 55149

Drop:  10.6m

Dominance:  1.16%

 

 

Pt. 901.8m

Summit Height:  901.8m (converted to OSGM15)

Summit Grid Reference:  SH 62258 55130

Bwlch Height:  892.5m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 62268 55133 (LIDAR)

Drop:  9.3m

Dominance:  1.03%

 

 

Pt. 906.2m

Summit Height:  906.2m (converted to OSGM15)

Summit Grid Reference:  SH 61983 55146

Bwlch Height:  896.1m (converted to OSGM15)

Bwlch Grid Reference:  SH 61885 55154

Drop:  10.1m (Welsh Highland Sub Reinstatement)

Dominance:  1.11%

 

 

Pt. 563.0m

Summit Height:  563.0m (converted to OSGM15)

Summit Grid Reference:  SH 63821 55162

Bwlch Height:  552.8m (converted to OSGM15)

Bwlch Grid Reference:  SH 63750 55175

Drop:  10.2m (Welsh Highland Sub addition)

Dominance:  1.82%

 

 

Carreg Gwalch

Summit Height:  546.0m (converted to OSGM15)

Summit Grid Reference:  SH 64238 55249

Bwlch Height:  531.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 64229 55166

Drop:  14.7m (Welsh Highland Sub addition)  

Dominance:  2.70%

 

 

For further details please consult the Trimble Survey Spreadsheet