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

Mapping Mountains – Trimble Surveys – Glyder Fawr

04.03.23  Pt. 924.4m (SH 659 585), Castell y Gwynt (SH 653 581), Pt. 929.0m (SH 656 579) and Pt. 872.3m (SH 658 577) 

Today I wanted to survey a number or rocky peaks on Glyder Fach.  Early travel writers would often overuse the word stupendous to describe the natural features of Eryri, but this mountain truly deserves the adjective.  I set off from Pen y Gwryd under leaden skies.  The conditions were mild and the mist was confined to elevations above 900m.  Upon reaching the plateau above Llyn Caseg Fraith, I noticed that my surveying plans may be compromised by the presence of snow that was earlier blanketed by the clouds.  This was unexpected and I was not equipped with winter mountaineering gear. 

The mist enshrouded ridge (Photo: Aled Williams)

My original plan was to first descend to Bwlch Tryfan to then ascend the north ridge of the mountain, thus allowing the surveying of some of its impressive pinnacles.  However, the snow conditions looked threatening.  Knowing that the most difficult scrambling was found on the lower half of the ridge, I decided that I would first ascend to the top of Glyder Fach and then investigate whether a descent to the pinnacles on the ridge was possible.  As the upper slopes of Glyder Fach were gained, the prospect became increasingly ominous!

An expanse of mist and snow (Photo: Aled Williams) 

By the time I had reached the high plateau of the mountain, I was in cloud.  It was a monochrome scene, the whiteness of the snow and sky interrupted by the dark outlines of naked rock.  The absence of wind provided a quiet stillness; another world to that found below the cloud.  The top of the north ridge came into view, which signalled decision time.  Would I venture down along its serrated snow-clad edge?

Top of the ridge (Photo: Aled Williams)

My feet awkwardly crested the first few boulders.  I slipped slightly and sensed the plunge that waited down to the recesses of Cwm Bochlwyd.  Compensating my weight to the right, another wave of exposure greeted me as I spied the rime-encrusted rocks disappearing into the void of Cwm Tryfan.  Luckily, there was no ice and this provided me the confidence to move forward slowly and carefully.

Looking down the upper section of the ridge (Photo: Aled Williams)

I eventually arrived at my first survey point of the day.  This was a narrow gap in the ridge at the top of a steep gully, which provided the land bridge between the highest pinnacle and the bulk of the mountain.  The pinnacle itself looked inaccessible and I doubted whether I would be able to climb it in the conditions for the purpose of measuring its height.  The primary target of the day was immediately behind the highest pinnacle, a peak that stood a chance of making P10 status and therefore inclusion into the Subs of The Welsh Highlands list.  Unfortunately, it soon became apparent that I would not be able to survey it, since the routes to it were too dangerous in the conditions.

The upper pinnacle (Photo: Aled Williams)

Having accepted that the lower pinnacles were out of reach, I focused on surveying the highest pinnacle.  The critical bwlch was quickly located and the Trimble was placed in position.  It took around ten minutes for the equipment to attain its optimal accuracy levels, hampered by the enclosed nature of the location.  This wait provided time for devising a strategy that would allow the top of the pinnacle to be measured for absolute height.  The strategy was duly executed and it quickly became apparent that I would not be able to place the Trimble at the highest point of rock.  However, by jamming my body in a cleft between two rocks and awkwardly contorting upwards, I was able to attain a position where the equipment could be held in place just below the summit.  A long two minute wait ensued as data was collected, at the end of which I had lost all sensation in my fingers!  The offset between he Trimble antenna and the highest point was taken before I gingerly descended to the relative safety of the bwlch.

Back on relative terra-firmer (Photo: Aled Williams)

I then re-traced my route upwards along the ridge.  I was glad to reach the high plateau again, happy that the morning’s adventure was at an end.  The next objective was Castell y Gwynt, although a quick visit to the summit of Glyder Fach provided a prelude.  

The summit area of Glyder Fach (Photo: Aled Williams)

Castell y Gwynt (SH 653 581) (Photo: Aled Williams)

The climb up Castell y Gwynt was completed with relatively little difficulty and the Trimble was soon gathering data on the highest rock.  I felt perched as I looked down on the plateau below.  Once descended the critical bwlch was located and the equipment was soon beeping away again as yet another data set was collected.  As I sat waiting, I admired the rock architecture of this fine top with its cathedral-like spires seemingly piercing the sky above.  However, my ruminations were suddenly interrupted by two ice-axe-equipped individuals creeping up towards the Trimble as they contemplated a route up the peak.  I greeted them with: “If you could steer clear of the yellow thing that would be appreciated”, to which one replied: “what is it?”, and without explanation I shouted “a GPS”!  Nothing more was said apart from a “thank you” as they retreated on to other things.

The bwlch of Castell y Gwynt (Photo: Aled Williams)

The penultimate tor to gather data from (Photo: Aled Williams)

There were two other tors that I wanted to survey on the way back to Pen y Gwryd.  These have always caught my attention when travelling along the road from the south and their surveys were long overdue.  The first proved to be another dramatic top, with a pleasing view down to Cwm Ffynnon.

One of the two rock tors surveyed on the descent (Photo: Aled Williams)

The last surveying objective of the day (Photo: Aled Williams)

The second top stood at the limit of the snowline.  Its form consisted of a terrace made up of huge pillars, permeated by deep cracks and chimneys.  Two summits were investigated with data gathered on each, despite the eye having judged the western point to be comfortably higher.  All that remained was a steady plod back to the car to bring another good day on the hill to a close. 

Aled Williams (March 2023) 

 

Survey Result:

 

Pt. 924.4m

Summit Height:  924.4m (converted to OSGM15)

Summit Grid Reference:  SH 65975 58541

Bwlch Height:  917.8m (converted to OSGM15)

Bwlch Grid Reference:  SH 65971 58536

Drop:  6.6m

Dominance:  0.72%

Castell y Gwynt

Summit Height:  975.7m (converted to OSGM15) (average of two Trimble GeoXH 6000 surveys) (significant height revision)

Summit Grid Reference:  SH 65397 58181

Bwlch Height:  959.7m (converted to OSGM15)

Bwlch Grid Reference:  SH 65419 58194

Drop:  16.0m

Dominance:  1.64%

Pt. 929.0m

Summit Height:  929.0m (converted to OSGM15)

Summit Grid Reference:  SH 65625 57979

Bwlch Height:  921.1m (converted to OSGM15)

Bwlch Grid Reference:  SH 65639 57995

Drop:  7.9m

Dominance:  0.85%

Pt. 872.3m

Summit Height:  872.3m (converted to OSGM15)

Summit Grid Reference:  SH 65867 57758

Bwlch Height:  867.0m (converted to OSGM15)

Bwlch Grid Reference:  SH 65876 57793

Drop:  5.3m (Welsh Highland Sub deletion)

Dominance:  0.61%

For details on the 1st survey of Castell y Gwynt

For further details please consult the Trimble Survey Spreadsheet

 

  

Mapping Mountains – Trimble Surveys – Moel Siabod

25.02.23  Moel Siabod (SH 705 546, only bwlch surveyed) and Cefn y Cerrig (SH 674 545) 

Having scrutinised several OS maps a circular walk was devised from the viewing-point car park (SH 658 541) between Llyn Gwynant and Pen y Gwryd.  I had never started a hill walk from this point and found the idea rather novel.  I arrived just after 8am and soon set off along the road to Pen y Gwryd, flanked by a stunning view of Yr Wyddfa.  Remnants of recent snowfall speckled the upper slopes and the buffeting of a cold north-easterly reminded me that winter was not yet over. 

Yr Wyddfa looking resplendent as ever (Photo: Aled Williams)

As I approached Pen y Gwryd, the masses bound for Yr Wyddfa were already filling up the available roadside car parking spaces.  I slipped by unnoticed as I headed to the first of my surveying objectives; the critical bwlch of Moel Siabod.  I had assisted Myrddyn Phillips with the survey of this pass back in 2017 and was eager to collect a couple of extra data sets given that the drop result was so close to the 600m prominence threshold for Major status (hills that appear in Mark Trengove’s list The Major Mountains of Britain and Ireland).  Two data sets were taken at the bwlch, each involving a lonely five-minute vigil in the numbing chill of the north wind. 

Gathering data at the bwlch of Moel Siabod (Photo: Aled Williams)

The view toward Cefn y Cerrig (Photo: Aled Williams)

Having packed away the Trimble, I headed towards the high point of the day; the potential new Welsh Highlands Sub of Cefn y Cerrig.  It felt good to be out on the open mountain, although the underfoot conditions made the traverse of the moor a squelchy affair.  Drier conditions prevailed once on the arm of Cefn y Cerrig was reached and a leisurely walk soon brought me to the base of the summit tor. 

The view of Dyffryn Mymbyr (Photo: Aled Williams) 

Gathering data at the summit of Cefn y Cerrig (Photo: Aled Williams)

I had visited the summit of Cefn y Cerrig once before in December 2005 and my memory of it as a fine rocky top was affirmed by the stunning view of Dyffryn Mymbyr.  This time, there was work to do.  The high point was duly located and the Trimble was placed into position for measurement.  During data collection I sheltered in comfort on the south-western side of the summit rocks and spied my descent route. 

Gathering data at the bwlch of Cefn y Cerrig with Yr Wyddfa as backdrop (Photo: Aled Williams)

Cefn y Cerrig (Photo: Aled Williams)

Once the Trimble had completed its task, I scrambled down the rocky facade of Cefn y Cerrig to the bwlch connecting it to its parent peak; Clogwyn Bwlch y Maen.  The critical position was located beside a partially frozen pool and the final data set of the day was gathered shortly afterwards.  The ground between Cefn y Cerrig and the car was pathless and wet, but quick progress was made regardless.  The sudden appearance of Llyn Gwynant signalled my imminent arrival back at the car and the end of an enjoyable morning on the hill.

Heading down from the hill (Photo: Aled Williams)

 

Survey Result: 

 

Moel Siabod

Summit Height:  872.2m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Summit Grid Reference:  SH 70524 54631 (from previous Trimble GeoXH 6000 survey)

Bwlch Height:  272.3m (converted to OSGM15)

Bwlch Grid Reference:  SH 66044 55603 (from previous Trimble GeoXH 6000 survey)

Drop:  599.9m (P600 Major deletion)

Dominance:  68.78%  

Cefn y Cerrig

Summit Height:  502.0m (converted to OSGM15)

Summit Grid Reference:  SH 67480 54509

Bwlch Height:  491.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 67511 54413

Drop:  10.8m (Welsh Highland Sub addition)

Dominance:  2.14%

For details on the 1st bwlch survey of Moel Siabod

For details on the summit survey of Moel Siabod

For further details please consult the Trimble Survey Spreadsheet