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

Llan Ucha Castell Madog (SO 027 385) – 390m Double Sub-Pedwar deletion

There has been a deletion 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 conducted by Myrddyn Phillips. 

LIDAR image of Llan Ucha Castell Madog (SO 027 385)

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 Y Pedwarau list are five categories of sub hills, with this hill being deleted from the 390m Double Sub-Pedwar category.  The criteria for this category being all Welsh hills at or above 390m and below 400m 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 now listed by is Llan Ucha Castell Madog and this was derived from the Tithe map, and it is adjoined to the Mynydd Epynt group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4520 road to its west and a minor road to its east, and has the small community of Capel Uchaf (Upper Chapel) towards the north-west.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub 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 21m of drop, based on the 399m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website which was entitled the Interactive Coverage Map and an estimated c 378m bwlch height, based on interpolation of 10m contouring between 370m – 380m. 

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

One of the resources recently available online is the mapping on the OS Maps website and the details for this hill were subsequently re-assessed against this mapping.  This is the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local.  This mapping had an uppermost 400m ring contour and bwlch contouring between 380m – 385m, with interpolation giving an estimated c 18m of drop.  Through discussion it was decided to wait for full LIDAR coverage before reassessing the status of this hill.

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 confirmation of the deletion of this hill from 390m Double Sub-Pedwar status is due to LIDAR analysis, resulting in a 400.7m summit height and a 381.6m bwlch height, with these values giving this hill 19.1m of drop, which is insufficient for it to be classified as a 390m Double Sub-Pedwar. 

 

The full details for the hill are:

Group:  Mynydd Epynt 

Name:  Llan Ucha Castell Madog 

OS 1:50,000 map:  160

Summit Height:  400.7m (LIDAR)                                                           

Summit Grid Reference:  SO 02707 38531 (LIDAR) 

Bwlch Height:  381.6m (LIDAR) 

Bwlch Grid Reference:  SO 02779 38800 & SO 02780 38801 (LIDAR) 

Drop:  19.1m (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 (July 2024)