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

 

Esgair Wen (SN 807 664) – 400m Sub-Pedwar reclassified to 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 LIDAR analysis conducted by Aled Williams. 

LIDAR image of Esgair Wen (SN 807 664)

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 Y Pedwarau list are five categories of sub hills, with this hill being reclassified from 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 isco-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 Esgair Wen and it is adjoined to the Drygarn Fawr group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north-west, west south-west and  east south-east, and has the village of Pontrhydfendigaid 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 included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 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 30m of drop, based on the 496m summit spot height that appeared on the contemporary Ordnance Survey 1:25,000 Explorer map, and an estimated c 466m bwlch height, based on interpolation of 10m contouring between 460m – 470m. 

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

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.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 465m bwlch spot height, and when coupled with its 496m summit spot height these values gave this hill 31m of drop, and these are the values given this hill when the 1^st edition of the Y Pedwarau 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.

The details for this hill were analysed using what is now the archived Welsh LIDAR, resulting in a 494.6m summit height and a 464.7m bwlch height, with these values giving this hill 29.9m of drop and therefore it was reclassified to 400m Sub-Pedwar status.

However, new Welsh LIDAR has now been used to analyse the details for this hill, resulting in a 494.8m summit height and a 464.8m bwlch height, with these values giving this hill 30.0m of drop, which is sufficient for it to be reinstated to Pedwar status. 

 

The full details for the hill are:

Group:  Drygarn Fawr 

Name:  Esgair Wen 

OS 1:50,000 map:  135, 136, 147

Summit Height:  494.8m (LIDAR) 

Summit Grid Reference:  SN 80767 66474 (LIDAR) 

Bwlch Height:  464.8m (LIDAR) 

Bwlch Grid Reference:  SN 80123 66302 (LIDAR) 

Drop:  30.0m (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 (September 2023)