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

 

Esgair Saeson (SN 795 603) – 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 Aled Williams. 

LIDAR image of Esgair Saeson (SN 795 603)

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 list are five categories of sub hills, with this hill being included in 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 name the hill is listed by is Esgair Saeson 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 a minor road to its north-west and south, and has the small community of Pontrhydfendigaid towards the north-west and the town of Tregaron 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 Hills to be surveyed sub list, as with a 500m summit spot height that appears on the contemporary Ordnance survey 1:50,000 Landranger and 1:25,000 Explorer map, its height was above the criterion used for this list.

With a summit spot height of 500m this hill was subsequently listed in the 500m Twmpau, and included in the accompanying sub list with an estimated c 24m of drop, based on the 500m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 476m bwlch height, based on interpolation of 10m contouring between 470m – 480m. 

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

Since the original compilation of this list 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 475m bwlch spot height positioned at SN 79101 60658, and when coupled with its 500m summit spot height these values gave this hill 25m of drop.

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 bwlch contouring between 470m – 475m, with interpolation placing the height of the bwlch as an estimated c 473m, resulting in its drop value being amended to an estimated c 27m.

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 inclusion of this hill as a 400m Sub-Pedwar is due to LIDAR analysis, resulting in a 498.4m summit height and a 473.8m bwlch height, with these values giving this hill 24.6m of drop, with its height sufficient for it to be classified as a 400m Sub-Pedwar.

                                     

The full details for the hill are:

Group:  Esgair Wen

Name:  Esgair Saeson

OS 1:50,000 map:  146, 147

Summit Height:  498.4m (LIDAR)

Summit Grid Reference:  SN 79504 60391 (LIDAR)

Bwlch Height:  473.8m (LIDAR)

Bwlch Grid Reference:  SN 79174 60567 (LIDAR)   

Drop:  24.6m (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 (November 2023)