Mapping Mountains – Hill Reclassifications – Y Pedwarau - The 400m Hills of Wales

Craig y Greigddu (SH 665 310) - 400m Sub Pedwar reclassified to Pedwar

There has been a reclassification to the listing of the Y Pedwarau – The 400m Hills of Wales, 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 Myrddyn Phillips and assisted by Mark Trengove.

Craig y Greigddu (SH 665 310)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being reclassified from the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format. 

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Craig y Greigddu and this was derived from research conducted by Aled Williams, and it is adjoined to the Y Llethr group of hills, which are situated in the western part of North Wales (Region C1, Sub-Region C1A), and it is positioned with minor roads to its west north-west and south-east, and has the village of Trawsfynydd towards the north-east.

When the original 400m height band of Welsh P30 hills compiled by Myrddyn Phillips was published on Geoff Crowder’s v-g.me website, this hill was not included in either the main P30 list or the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for each category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 27m of drop, based on the 499m 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 472m bwlch height, based on interpolation of 10m contouring between 470m – 480m that appear on the Ordnance Survey 1:25,000 Explorer map.

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

However, it was not until the survey with the Trimble GeoXH 6000 that an accurate summit and bwlch height and therefore also drop could be given this hill.

The Trimble GeoXH 6000 gathering data at the summit of Craig y Greigddu

The Trimble GeoXH 6000 gathering data at the bwlch of Craig y Greigddu

Therefore, the reclassification of this hill from 400m Sub-Pedwar status is due to a Trimble GeoXH 6000 survey, resulting in a 499.5m summit height and a 469.2m bwlch height, with these values giving this hill 30.3m of drop, which is sufficient for it to be classified as a Pedwar.  

The full details for the hill are:

Group:  Y Llethr

Name:  Craig y Greigddu

OS 1:50,000 map:  124

Summit Height:  499.5m (converted to OSGM15)

Summit Grid Reference:  SH 66565 31003

Bwlch Height:  469.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 66658 31203

Drop:  30.3m

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

Myrddyn Phillips and Aled Williams (September 2014)