Coed Bryndansi (SH 855 740) – Sub-Trichant reclassified to
Trichant
There has been confirmation of a reclassification
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.
The criteria for the list that this
reclassification applies to are:
Y Trichant
– The 300m Hills of Wales – Welsh
hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the
Sub-Trichant with the criteria for
this sub category being all Welsh hills at or above 300m and below 400m in
height with 20m or more and below 30m of drop.
The list is authored by
Myrddyn Phillips, with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13th May 2017.
The name the hill is listed
by is Coed Bryndansi and it is adjoined to the Rhos group
of hills which are situated in the northern part of North Wales (Region A,
Sub-Region A2), and it is positioned with the B5381 road to its north, the
B5113 road to its west and minor roads to its south and east, and has the
village of Llansanffraid Glan Conwy towards the west north-west.
When the original 300m 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 list.
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 estimated with c 27m of drop, based on an
estimated c 303m summit height and an estimated c 276m bwlch height with the
latter based on interpolation of 10m contouring between 270m – 280m.
Extract from the Ordnance Survey 1:25,000 Explorer map |
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 and also for this area it had
contour intervals at 5m. This
re-assessment resulted in this hill being listed with c 30m of drop based on an
estimated c 303m summit height and an estimated c 273m bwlch height with the
latter based on interpolation of 5m contouring between 270m – 275m.
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 also resulted in an
estimated bwlch height of c 273m resulting in a drop value of c 30m.
The estimated summit height was substantiated when
the Ordnance Survey series of Six-Inch maps were examined, as this mapping
shows a 995.1ft (303.1m) Surface height for this hill.
Extract from the Ordnance Survey series of Six-Inch maps |
When the Ordnance Survey Vector Map Local that was
hosted on the Geograph website and entitled the Interactive Coverage Map became
unavailable it was replaced with another Ordnance Survey product that showed a
number of spot heights not on other publicly available Ordnance Survey
maps. This latest mapping does not have
contours, but for this hill it shows a 304m summit spot height positioned at SH
85567 74121, which corresponds with the approximate position of the
aforementioned Surface height.
Extract from the Ordnance Survey non-contour Vector Map Local hosted on the Geograph wbsite |
Another resource now available online is the
WalkLakes website which hosts an interactive 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 it shows a 305m summit spot height positioned at SH 85531 74002.
Extract from the WalkLakes website |
Therefore, the confirmation of the reclassification
of this hill to Trichant status is due to detail derived from contemporary maps
produced from Ordnance Survey data, resulting in a 305m summit height and an
estimated bwlch height of c 273m, with these values giving this hill c 32m of
drop, which is sufficient for it to be classified as a Trichant.
The full details for the
hill are:
Group: Rhos
Name: Coed Bryndansi
OS 1:50,000 map: 116
Summit Height: 305m (spot height)
Summit Grid
Reference: SH 85531 74002 (spot height)
Bwlch Height: c 273m (interpolation)
Bwlch Grid
Reference: SH 85239 74303
(interpolation)
Drop: c 32m (spot height summit and interpolated
bwlch)
Myrddyn Phillips (March
2020)
No comments:
Post a Comment