Myrddyn Phillips - Mapping Mountains: Cefn y Cerrig

Showing posts with label Cefn y Cerrig. Show all posts

Friday, 5 May 2023

Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

Cefn y Cerrig (SH 674 545) – 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.

Cefn y Cerrig (SH 674 545) (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 Cefn y Cerrig and it is adjoined to the Moel Siabod group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A2), and it is positioned with the A4086 road to its north, the A498 road to its west and the A470 road to its south-east, and has the village of Capel Curig towards the north-east.

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

Prior to the survey with the Trimble GeoXH 6000 this hill was initially listed with an estimated c 9m of drop, based on the 502m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and an estimated c 493m bwlch height, based on interpolation of 10m contouring between 490m – 500m.

The Trimble GeoXH 6000 gathering data at the summit of Cefn y Cerrig. (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 502.0m summit height and a 491.2m bwlch height, with these values giving this hill 10.8m of drop, which is sufficient for it to be classified as a Welsh Highland Sub.

The full details for the hill are:

Group: Moel Siabod

Name: Cefn y Cerrig

OS 1:50,000 map: 115

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

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 (May 2023)

Wednesday, 12 April 2023

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.