Moving Mountain Summits

© Myrddyn Phillips

Prolific amateur hill surveyor Myrddyn Phillips 'discovers' a new summit for one of the Berwyn mountains of North Wales...

Foel Cedig stands out from afar as it has a small grassy knoll which gives the hill the impression of having a slightly raised summit - a contrast to its heather bound neighbours, the majority of which comprise high whale backed ridges that have rounded summits almost indistinguishable from the moor. However, the hill was thought to have little prominence as it is given a map height of 666m, whilst the neighbouring Cyrniau Nod has always been accepted as higher because of its 667m map height.

Foel Cedig on left with the deposed Cyrniau Nod on the right  © Myrddyn Phillips
Foel Cedig on left with the deposed Cyrniau Nod on the right
© Myrddyn Phillips

These two hills, Foel Cedig and Cyrniau Nod, form a part of the great swathe of wild land that comprise the Berwyn. This extensive range of hills stretches from the Afon Dyfrdwy (River Dee) as it passes the confines of Corwen and Llangollen in the north, all the way south to the hills above Dinas Mawddwy and the infant Afon Dyfi (River Dovey).

As Cyrniau Nod is higher according to Ordnance Survey maps it has always been considered the prioritised summit of these two hills, and with a prominence of 179m and a height over 600m it is both relatively high and relatively prominent. As such it is listed as a Marilyn, Hump, Simm, Hewitt, Uchaf and Nuttall:

  • Marilyn: British hills with 150m minimum drop irrespective of their height
  • Hump: British hills with 100m minimum drop irrespective of their height
  • Simm: British hills with 600m minimum height and 30m minimum drop
  • Hewitt: English, Welsh and Irish hills with 2,000ft (609.6m) minimum height and 30m minimum drop
  • Uchaf: This is the working title for a list comprising Welsh hills with 500m minimum height and 15m minimum drop
  • Nuttall: English and Welsh hills with 2,000ft (609.6m) minimum height and 15m minimum drop

However, the surveying method of photogrammetry that ascertained the map height of Foel Cedig has a margin of uncertainly of +/- 3m, whilst the map height given Cyrniau Nod is based on a series of levelled heights which are more accurate. So could Foel Cedig in fact be higher than Cyrniau Nod? There was only one way to find out; visit both hills and accurately survey their summits.

It was a breezy morning setting off from the high road at it passes over the upper part of Cwm Hirnant to the west of these hills, and with heavy overnight rain and a forecast of morning showers I did not want to linger.

A track skirting the summits of a number of heather bound hills eases access, and I used this to make forays to each as I slowly made surveying progress to the prioritised surveys of Foel Cedig and Cyrniau Nod.

To survey these hills I used a Trimble GeoXH 6000 which is a GNSS receiver capable of measurement to within and better than 0.1m in height. As it has an internal antenna and only weighs 2lb it does not require an additional antenna, pole and tripod, therefore its portability and its accuracy over a five minute period of data collection are huge advantages when out on the hill.

The track across the moor leading toward Foel Cedig  © Myrddyn Phillips
The track across the moor leading toward Foel Cedig
© Myrddyn Phillips

The summit of Foel Cedig comprises an attractive knoll with exposed rock and is easily distinguished from surrounding ground. To give the Trimble elevation above its immediate surrounds I usually place the equipment on top of my rucksack, using this as an improvised tripod, and this is what I did for each summit.

Having taken a ten minute data set I continued through the heather and bog toward Cyrniau Nod. John Barnard and I had surveyed this hill with a level and staff for summit position in June 2014, and once at its summit this is where I placed the Trimble and gathered another ten minute data set. So what of the results?

The Trimble GeoXH 6000 results are given below:

  • Foel Cedig – 667.4m summit at SH 98170 28327
  • Cyrniau Nod – 666.2m summit at SH 98847 27920

Therefore, as Foel Cedig is 1.2m higher than Cyrniau Nod, the prioritised summit is relocated to the attractive rock exposed knoll of Foel Cedig.

This information may be met with gasps of woe by any hill walker who has visited this area to bag either a Marilyn, Uchaf or Nuttall, as except for those who purposely diverted to visit Foel Cedig with the understanding that its map height has such a margin of uncertainty, the summit would no doubt have been bypassed.

Alan Dawson, the author of the Marilyns, Hewitts and Simms has been informed of this result and accepted the summit relocation, as have the authors of the Uchafion list, Aled Williams and Myrddyn Phillips (that's me!); will John and Anne Nuttall follow suit? We'll have to wait and see.

24 Aug, 2018

I really like Cyrniau Nod when I climbed it (On the way from Llangynog to Bala) about a decade back. Vast swathes of heather and the main Aran scarp looking quite dramatic in the distance. Foel y Geifr is better than either, if slightly lower.

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