Pt. 357.9m (SH 939 029) – Sub-Trichant addition
There has been confirmation of an addition to the
list of Y Trichant – The 300m 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 and LIDAR analysis
conducted by Myrddyn Phillips.
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LIDAR image of Pt. 357.9m (SH 939 029) |
The criteria for the list that this addition
applies to are:
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Y Trichant - The 300m Hills of Wales by Myrddyn Phillips |
The hill is being listed by the point (Pt. 357.9m)
notation as an appropriate name for it either through local enquiry and/or
historic research has not been found by the author, and it is adjoined to the Carnedd
Wen group of hills, which are situated in the southern
part of North Wales (Region A, Sub-Region A3), and it is positioned with the A470 road to its south-west
and a minor road to its south-east, and has the village of Talerddig towards
the south.
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 23m of drop, based on
the 358m summit spot height that appeared on the Ordnance Survey Vector Map
Local hosted on the Geograph website and which was entitled the Interactive
Coverage Map and an estimated c 335m bwlch height, based on interpolation of
10m contouring between 330m – 340m that appears on the Ordnance Survey 1:25,000
Explorer map.
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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.
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 330m
– 335m, with interpolation placing the height of the bwlch as an estimated c 334m,
giving this hill an estimated c 24m of drop.
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 addition of
this hill to Sub-Trichant status is due to LIDAR analysis and detail on
contemporary maps produced from Ordnance Survey data, resulting in a 357.9m
summit height and an estimated c 334m bwlch height, with these values giving
this hill an estimated c 24m of drop, which is sufficient for it to be
classified as a Sub-Trichant.
The full details for the
hill are:
Group: Carnedd Wen
Name: Pt. 357.9m
OS 1:50,000 map: 136
Summit Height: 357.9m (LIDAR)
Summit Grid
Reference: SH 93969 02971 (LIDAR)
Bwlch Height: c 334m (interpolation)
Bwlch Grid
Reference: SH 94097 02750 (interpolation)
Drop: c 24m (LIDAR summit and interpolated bwlch)
Myrddyn Phillips
(September 2022)
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