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

Carreg y Gwynt (SN 956 776) - Pedwar reclassified to 400m Sub-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 LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips.

LIDAR image of Carreg y Gwynt (SN 956 976)

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 Y Pedwarau list are five categories of sub hills, with this hill being reclassified to 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 Carreg y Gwynt and it is adjoined to the Hirddywel group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B2), and it is positioned with minor roads to its north and south, the A470 road to its west and the B4518 road to its east, and has the town of Llanidloes towards the north.

When The 400m Peaks of Wales list presented in a file entitled The 400m Hills of England, Isle of Man and Wales was published in 2002 on the RHB Yahoo Group file database this hill was included in the accompanying P20 sub list.

When the 400m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, the details for this hill had been reassessed, based on a 104ft (31.7m) basic levelling survey conducted by Myrddyn Phillips on the 23.04.04.  Therefore, it was included in the main P30 list with a 428m summit height based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

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.

Therefore, the reclassification of this hill to 400m Sub-Pedwar status is due to LIDAR analysis, resulting in a 426.9m summit height and a 398.6m bwlch height, with these values giving this hill 28.3m of drop, which is insufficient for Pedwar status.

The full details for the hill are:

Group:  Hirddywel

Name:  Carreg y Gwynt  

OS 1:50,000 map:  136, 147

Summit Height:  426.9m (LIDAR )  

Summit Grid Reference:  SN 95698 77667 (LIDAR)  

Bwlch Height:  398.6m (LIDAR)

Bwlch Grid Reference:  SN 95153 78741 (LIDAR)

Drop:  28.3m (LIDAR)  

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 (March 2017)