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

Pt. 428.2m (SN 731 497) – 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 detail on contemporary Ordnance Survey maps, with confirmation of the status change from subsequent LIDAR analysis.

LIDAR image of Pt. 428.2m (SN 713 497)

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 list are five categories of sub hills, with this hill being reclassified 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 hill is being listed by the point (Pt. 428.2m) notation, 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, south and east, and has the village of Llanddewi Brefi towards the north-west.

When the original 400m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for the main P30 category. 

When 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 30m of drop, based on the 427m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 397m bwlch height, based on interpolation of 10m contouring between 390m – 400m, and the above details were used when the hill was listed in the 1^st edition of the Y Pedwarau published by Europeaklist in May 2013.

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

Since publication of the 1^st edition of the Y Pedwarau there are Ordnance Survey maps that are now also available online.  The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps; however the details for this hill remained the same as no additional spot heights appear on this map.

The details for this hill were also re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has contours at 5m intervals which are proving consistently more accurate compared to the 5m contours that sometimes appear on Ordnance Survey 1:25,000 Explorer maps and used to appear on the online Vector Map Local.  This latest re-assessment resulted in the hill being listed with an estimated c 29m of drop, based on interpolation of 5m bwlch contouring between 395m – 400m.

Extract from the OS Maps website

Another resource now available online is the WalkLakes website which hosts an interactive Ordnance Survey map originated from the Ordnance Survey Open Data programme.  This map has many spot heights not on other publicly available Ordnance Survey maps and for this hill a 427m summit spot height also appears in the same position as it does on the Ordnance Survey 1:25,000 Explorer map, however the bwlch contours are between 400m – 410m which if taken would give this hill a lower value that the estimated c 29m of drop.

Extract from the interactive mapping hosted on the WalkLakes 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.

Therefore, the confirmation of the reclassification of this hill from Pedwar to 400m Sub-Pedwar status is due to LIDAR analysis, resulting in a 428.2m summit height and a 399.0m bwlch height, with these values giving this hill 29.2m of drop.

The full details for the hill are:

Group:  Esgair Wen  

Name:  Pt. 428.2m

OS 1:50,000 map:  146, 147

Summit Height:  428.2m (LIDAR)

Summit Grid Reference:  SN 73159 49742 (LIDAR)

Bwlch Height:  399.0m (LIDAR)

Bwlch Grid Reference:  SN 72736 49808 & SN 72739 49810 (LIDAR)

Drop:  29.2m (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 (February 2020)