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

 

Crug Siarls (SN 702 483) – 390m Sub-Pedwar deletion

There has been a deletion from 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 conducted by Myrddyn Phillips. 

LIDAR image of Crug Siarls (SN 702 483)

The criteria for the list that this deletion 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 deleted from the 390m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 390m and below 400m in height that have 30m minimum 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 Crug Siarls, and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its west and south, the B4343 road farther to its west, and the A482 road farther to its south-west, and has the town of Llanbedr Pont Steffan (Lampeter) towards the west.

When the original 300m height band of Welsh P30 hills compiled by Myrddyn Phillips was published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list with a 391m summit height, based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

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

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 54m of drop, based on the 391m summit spot height and the 337m bwlch 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 these are the details giiven the hill when the 1^st edition of the Y Pedwarau, now co-authored by Myrddyn Phillips and Aled Williams was published by Europeaklist in May 2013.

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 deletion of this hill from 390m Sub-Pedwar status is due to LIDAR analysis, resulting in a 389.7m summit height and a 336.8m bwlch height, with these values giving this hill 52.9m of drop, with the summit height insufficient for it to be classified as a 390m Sub-Pedwar.                                         

 

The full details for the hill are:

Group:  Esgair Wen

Name:  Crug Sials

OS 1:50,000 map:  146, 147

Summit Height:  389.7m (LIDAR)

Summit Grid Reference:  SN 70220 48343 (LIDAR)

Bwlch Height:  336.8m (LIDAR)

Bwlch Grid Reference:  SN 69635 48220 (LIDAR)   

Drop:  52.9m (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 (February 2026)