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

Pt. 415.1m (SO 072 065) – 400m Sub-Pedwar addition

There has been an addition 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 Pt. 415.1m (SO 072 065)

The criteria for the list that this addition 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 added 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 hill is being listed by the point (Pt. 415.1m) notation and it is adjoined to the Cefn yr Ystrad group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with the A4060 road to its north-west and a minor road to its south, and has the town of Merthyr Tudful towards the west.

When the original 400m height band of Welsh P30 hills was 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.

This hill is a recent man-made construction and has undergone extensive terra-forming in the interim between the original compilation of this list and nowadays when independent surveyors, the availability of LIDAR and more detailed online mapping all give opportunity for increased numerical accuracy.  However, due to quarrying activity no contours of note appear on the contemporary Ordnance Survey 1:50,000 Landranger and 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 were 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. 

LIDAR image of Pt. 415.1m (SO 072 065)

Although it was LIDAR that first distinguished the validity of this hill it is worth making note of its details on other mapping.  Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online.  Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website.  Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites.

One of the mapping resources now available online is the WalkLakes website which hosts an interactive map originated from the Ordnance Survey Open Data programme.  This map has many spot heights not on other publicly available maps and a 374m, 384m and a 397m spot height appear in the vicinity of the summit of this hill. 

Extract from the interactive mapping hosted on the WalkLakes website

Another resource now available online is the interactive mapping hosted on the Welsh Government website and entitled the DataMapWales.  This mapping has 5m contours and its detail matches that produced from the OS Terrain 5 product, which compliments much of that produced from LIDAR, and for this hill it has an uppermost 415m ring contour. 

Extract from the interactive mapping entitled the DataMapWales

Therefore, the addition of this hill to 400m Sub-Pedwar status is due to LIDAR analysis, resulting in a 415.1m summit height and a 389.8m bwlch height, with these values giving this hill 25.3m of drop, which is sufficient for it to be classified as a 400m Sub-Pedwar. 

 

The full details for the hill are:

Group:  Cefn yr Ystrad 

Name:  Pt. 415.1m 

OS 1:50,000 map:  160

Summit Height:  415.1m (LIDAR) 

Summit Grid Reference:  SO 07212 06536 (LIDAR) 

Bwlch Height:  389.8m (LIDAR) 

Bwlch Grid Reference:  SO 07596 06528 (LIDAR) 

Drop:  25.3m (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 (July 2023)