Wenlli (SH 845 655) – 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 Ordnance Survey maps.
LIDAR image of Wenlli (SH 845 655) |
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 now listed by
is Wenlli and this was derived from the Tithe map, 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 B5113 road to its west and the
A548 road to its south and east, and has the town of Llanrwst towards the
south-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.
Extract from the Ordnance Survey 1:25,000 Explorer map |
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 listed with an estimated c 30m of drop, based on the
twin 308m map heighted summits with the prioritised summit position given to
the spot height that appears at SH 846 654 on Ordnance Survey 1:25,000 Explorer
maps, and an estimated c 278m bwlch height.
The details for this hill were re-examined 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.
However, as this mapping had no additional spot heights of note the
details for this hill remained the same.
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 re-assessment resulted in the hill being
listed with an estimated c 277m bwlch height based on interpolation of 5m contouring
between 275m – 280m and therefore increasing its drop value to c 31m.
During these re-assessments the position of this
hill’s summit was relocated to match a hand-held GPS position submitted to
DoBIH, and although an accurate survey would be needed to confirm this
position, for now it is being taken for that of the summit.
Therefore, the reclassification of this hill from Sub-Trichant
status is due to detail derived from contemporary Ordnance Survey maps,
resulting in a 308m summit height and an estimated 277m bwlch height, with
these values giving this hill c 31m of drop, which is sufficient for it to be
classified as a Trichant.
The full details for the
hill are:
Group: Rhos
Name: Wenlli
OS 1:50,000 map: 116
Summit Height: 308m (spot height)
Summit Grid
Reference: SH 84520 65553 (hand-held GPS
via DoBIH)
Bwlch Height: c 277m (interpolation)
Bwlch Grid
Reference: SH 83917 65689 (interpolation)
Drop: c 31m (hand-help GPS via DoBIH and
interpolated bwlch)
Myrddyn Phillips (March
2020)
No comments:
Post a Comment