Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

Pt. 872.3m (SH 658 577) – Welsh Highland Sub deletion 

There has been a deletion to the listing of the Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis and subsequently confirmed by a Trimble GeoXH 6000 survey, both conducted by Aled Williams. 

LIDAR image of Pt. 872.3m (SH 658 577)

The criteria for the list that this deletion applies to are:

Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

Welsh Highlands - Uchafion Cymru by Myrddyn Phillips and Aled Williams

The hill is being listed by the point (Pt. 872.3m) notation and it is adjoined to the Glyder Fawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A5 road to its north and the A4086 road to its south, and has the village of Capel Curig towards the east.

When the initial P10 sub list was completed in June 2020 this hill was listed with an estimated c 10m of drop, based on an 873m summit height and an estimated c 863m bwlch height, and therefore included as a Welsh Highland Sub when the drop value of the subs was agreed upon and revised in July 2020. 

Extract from the Ordnance Survey 1:25,000 Explorer map

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The Trimble GeoXH 6000 gathering data on Pt. 872.3m (SH 658 577).  Photo: Aled Williams

LIDAR analysis gave this hill under 10m of drop required for it to be classified as a Welsh Highland Sub, and as this hill had now been surveyed with the Trimble GeoXH 6000, it is this result that is being prioritised for this hill.

Therefore, the deletion of this hill from Welsh Highland Sub status is due to LIDAR analysis and subsequently confirmed by a Trimble GeoXH 6000 survey, resulting in an 872.3m summit height and an 867.0m bwlch height, with these values giving this hill 5.3m of drop, which is insufficient for it to be classified as a Welsh Highland Sub. 

 

The full details for the hill are: 

Group:  Glyder Fawr

Name:  Pt. 872.3m

OS 1:50,000 map:  115

Summit Height:  872.3m (LIDAR)

Summit Grid Reference:  SH 65867 57758 (LIDAR)

Bwlch Height:  867.0m (LIDAR)

Bwlch Grid Reference:  SH 65876 57793 (LIDAR)   

Drop:  5.3m (LIDAR) 

 

For the additions, deletions and reclassifications to the Welsh Highlands – Uchafion Cymru reported on Mapping Mountains please consult the following Change Registers:

 

Welsh Highland P15s

 

Welsh Highland Subs

 

Aled Williams and Myrddyn Phillips (July 2023)

 

 

  

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