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.
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LIDAR image of Esgair Saeson (SN 795 603) |
The criteria for the list that this addition applies
to are:
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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.
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.
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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)