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

Bryn Catel (SN 697 506) – 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 detail on contemporary maps produced from Ordnance Survey data, with confirmation of its addition from subsequent LIDAR analysis.

Bryn Catel (SN 697 506)

This was initiated by Joe Nuttall who produced a summit analysis programme that used LIDAR with an alternative height map (DEM) allowing identification of summits and bylchau and thereby drops.  The resulting spreadsheet that Joe produced contains over 29,600 hills.

This spreadsheet is being evaluated by a number of people, including Ronnie Bowron, who passed the details of this hill to us.

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 400m Sub-Pedwar status 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 Bryn Catel, 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 north, west and south, with the B4343 road farther to its west, and has the village of Llanddewibrefi towards the north-west.

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 the main P30 list or in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for either category. 

After the P30 lists were standardised, and interpolated heights and drop values also included, this hill was still not included, and neither was it when the 1^st edition of the Y Pedwarau co-authored by Myrddyn Phillips and Aled Williams was published by Europeaklist in May 2013; it had been completely missed.

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

Since publication of these 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 are current and digitally updated such as the mapping on the WalkLakes website, and it is this mapping that gives this hill a 426m summit spot height.

Extract from the interactive mapping hosted on the WalkLakes website

The details for this hill were also re-assessed against the mapping on the OS Maps website.  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 resulted in its bwlch height being listed as an estimated c 402m based on interpolation of 5m contouring between 400m – 405m.

Extract from the OS Maps website

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.

LIDAR image of Bryn Catel (SN 697 506)

Therefore, the confirmation of the addition of this hill to 400m Sub-Pedwar status is due to LIDAR analysis, resulting in a 424.9m summit height and a 399.8m bwlch height, with these values giving this hill 25.2m of drop, which is sufficient for it to be classified as a 400m Sub-Pedwar.

The full details for the hill are:

Group:  Esgair Wen

 

Name:  Bryn Catel

OS 1:50,000 map:  146

Summit Height:  424.9m (LIDAR)

Summit Grid Reference:  SN 69737 50673 (LIDAR)

Bwlch Height:  399.8m (LIDAR)

Bwlch Grid Reference:  SN 69777 50966 (LIDAR)

Drop:  25.2m (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 (October 2020)