Mapping Mountains – Significant Height Revisions – Welsh Highlands – Uchafion Cymru

Craig Eigiau (SH 712 646) 

There has been a Significant Height Revision to a hill that is listed in the Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey conducted by Aled Williams. 

Craig Eigiau (SH 712 646) (Photo: Aled Williams)

The criteria for the list that this height revision 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 name the hill is listed by is Craig Eigiau and it is adjoined to the Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with a minor road to its north-east, the A5 road to its south-west and the B5106 road and the A470 road to its east, and has the town of Llanrwst towards the east south-east.

The contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map do not show any meaning contours for this hill that imply its true height, as each only has an uppermost 670m contour. 

Extract from the Ordnance Survey 1:25,00 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.

LIDAR analysis gives this hill 9.7m of drop, based on a 688.1m summit height and a 678.4m bwlch height.  This hill has now been surveyed with the Trimble GeoXH 6000, resulting in a 688.4m summit height positioned at SH 71280 64670 and it is this result that is being prioritised for this hill, and this summit height comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

The Trimble GeoXH 6000 gathering data at the summit of Craig Eigiau (SH 712 646) (Photo: Aled Williams)

Therefore, the new listed summit height of this hill is 688.4m and this was derived from a Trimble GeoXH 6000 survey, this is positioned at SH 71280 64670 and is 18.4m higher than the uppermost 670m contour on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are: 

Group:  Carnedd Llywelyn

Name:  Craig Eigiau

OS 1:50,000 map:  115

Summit Height (New Height):  688.4m (converted to OSGM15)

Summit Grid Reference:  SH 71280 64670

Bwlch Height:  678.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 71218 64674   

Drop:  10.2m 

 

Aled Williams and Myrddyn Phillips (April 2023)

 

 

  

Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

Craig Eigiau (SH 712 646) – Welsh Highland Sub addition 

There has been an addition 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 a Trimble GeoXH 6000 survey conducted by Aled Williams. 

Craig Eigiau (SH 712 646) (Photo: Aled Williams)

The criteria for the list that this addition 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 name the hill is listed by is Craig Eigiau and it is adjoined to the Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with a minor road to its north-east, the A5 road to its south-west and the B5106 road and the A470 road to its east, and has the town of Llanrwst towards the east south-east. 

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

Prior to the survey with the Trimble GeoXH 6000 this hill was listed with 9.7m of drop, based on a 688.1m summit height and a 678.4m bwlch height, with both heights derived from LIDAR analysis conducted by Aled Williams.  Due to the marginal nature in the drop ascertained from LIDAR analysis, this hill was prioritised for a Trimble GeoXH 6000 survey and it is this result that is being prioritised. 

The Trimble GeoXH 6000 gathering data at the summit of Craig Eigiau (SH 712 646) (Photo: Aled Williams)

Therefore, the addition of this hill to Welsh Highland Sub status is due to a Trimble GeoXH 6000 survey, resulting in a 688.4m summit height and a 678.2m bwlch height, with these values giving this hill 10.2m of drop, which is sufficient for it to be classified as a Welsh Highland Sub. 

 

The full details for the hill are: 

Group:  Carnedd Llywelyn

Name:  Craig Eigiau

OS 1:50,000 map:  115

Summit Height:  688.4m (converted to OSGM15)

Summit Grid Reference:  SH 71280 64670

Bwlch Height:  678.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 71218 64674   

Drop:  10.2m 

 

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 (April 2023)

  

Mapping Mountains – Trimble Surveys – Carnedd Llywelyn

28.01.23  Craig Eigiau (SH 712 646) 

As the dawn became morning, a succession of steep hairpin bends gradually brought me to the farm of Rowlyn.  Having duly opened and closed a gate, I motored onwards along the narrow road to Cwm Eigiau with the high Carneddau ridge soon becoming visible, mottled with broken snow patches and enveloped with wisps of mist.  My progress then came to a sudden halt.  In front of me was an abandoned vehicle blocking the road with its offside front-wheel having broken off!  I jumped out of the car to inspect the grass beside the road and concluded that it was driveable to bypass the wreck.  The short offroad was tackled steadily and quickly and within a few minutes I had arrived at the car park in front of Llyn Eigiau. 

Breakdown (Photo: Aled Williams)

The plan for the morning was a north-south traverse of Craig Eigiau, with the objective being to survey a potential new P10 Sub-Top for The Welsh Highlands list.  Despite my early start, the car park was surprisingly almost full, with many having wild-camped on the hill the previous night.  Quick progress was made along the track that services the Melynllyn and Dulyn reservoirs and I soon found myself atop the first peak of the day, the Sub-Top of Clogwyn yr Eryr. 

Clogwyn yr Eryr (Photo: Aled Williams)

Dulyn (Photo: Aled Williams)

The views from this minor top were stunning, rewarding my earlier efforts in vacating the warmth of my bed in the dark depths of January!  To the south stretched Llyn Eigiau, perfectly reflecting the image of Pen Llithrig y Wrach that towered behind the lake.  To the west was the dark well of Dulyn, its cold waters gently coaxing mist downwards from the high Carneddau, with an alpine-like Carnedd Llywelyn sitting high above the cloudy scene. 

Carnedd Llywelyn (Photo: Aled Williams)

A series of chiselled outcrops appeared on the horizon, signalling my imminent arrival at the high point of the day, the 735.0m summit of Craig Eigiau.  Having crossed a bank of hard snow, a slippery scramble took me to the highest pinnacle of rock.  I stood at the summit for a few minutes admiring the rock architecture and the surrounding country, contemplating whether I had previously underrated the merits of this fine hill. 

The high point of the day (Photo: Aled Williams)

Craig Eigiau summit (Photo: Aled Williams)

With great expectation I headed southwards to survey the 688m summit of Craig Eigiau.  As I walked across the sodden expanse of montane grassland a frozen drizzle blew in from Carnedd Llywelyn.  Over my shoulder an arch of colour commanded my attention, transpiring as a rainbow straddling the Gletffordd plateau. 

Rainbow (Photo: Aled Williams)

Craig Eigiau rainbow (Photo: Aled Williams)

I was now face-to-face with my quarry, the Sub-Top of Craig Eigiau, resembling very much its higher neighbour albeit with muted grandeur.  A further belt of icy drizzle and mist blew in as I surveyed the critical bwlch of the hill, with data eventually gathered at two positions. 

The Sub-Top of Craig Eigiau (Photo: Aled Williams)

Summit of the Sub-Top (Photo: Aled Williams)

The high point proved relatively easy to identify, with an Abney level being used to verify the placement before data was collected with the Trimble.  As I headed down from the summit, a good number of alpine clubmoss (Diphasiastrum alpinum) plants were observed, being perfectly adept to the harsh winter environment on these mountains.  Also in their element were the mountain ponies of which the Carneddau claim their own unique breed of. 

Alpine clubmoss (Photo: Aled Williams)

Carneddau mountain ponies (Photo: Aled Williams)

A steep descent towards the old farm of Cwm Eigiau brought me onto the track that would lead me back to the awaiting car.  As I walked out of the valley, I thought about the people who once inhabited its upper regions, living their lives within its confines and thereby bringing a constant human presence.  In stark contrast, the Cwm Eigiau of today is a transient place.

Cwm Eigiau (Photo: Aled Williams)

 

Craig Eigiau (Photo: Aled Williams)

Aled Williams (January 2023) 

 

Survey Result: 

 

Craig Eigiau

Summit Height:  688.4m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SH 71280 64670

Bwlch Height:  678.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 71218 64674

Drop:  10.2m (Welsh Highland Sub addition)

Dominance:  1.48%

 

For further details please consult the Trimble Survey Spreadsheet