Gribin (SH 675 168) – 200m
Sub-Twmpau reclassified to 200m Twmpau
There has been confirmation of a reclassification to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:
200m Twmpau - Welsh hills at and above 200m and below 300m in height with 30m
minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all
Welsh hills at and above 200m and below 300m in height with 20m and more and
below 30m of drop, with the word Twmpau
being an acronym standing for thirty
welsh metre prominences and upward.
This hill was listed in the Hills to be surveyed sub list when the original Welsh P30 hills
were published on Geoff Crowder’s v-g.me website as it was thought not to meet the criteria then used for the main
P30 list; however this list has now been standardised and interpolated heights
and drop values also included, resulting in this hill being listed with an estimated c 39m of drop, based on an estimated c 211m
summit height and an estimated bwlch height of c 172m based on bwlch map contouring
between 170m – 180m. The details for
this hill were later amended when the Ordnance Survey Interactive Coverage Map
hosted on the Geograph website became available online and it was then listed
with a 211m summit height based on the spot height appearing on this map.
Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website |
The name of the hill is Gribin
and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales
(Region A, Sub-Region A3), it is positioned overlooking the A 493 road which is
to its north and has the small community of Arthog towards the south-west and
the town of Dolgellau towards the east.
The summit and upper southern
section of the hill is a part of designated open access land and a public
footpath leads toward this from the west south-west of the hill, with another
option for an ascent following a public footpath from the north-east of the
hill.
The confirmation of the
reclassification of Gribin to 200m Twmpau
status is due to LIDAR analysis conducted by Myrddyn Phillips. The LIDAR (Light Detection & Ranging)
technique produced highly accurate height data that is now freely available for
much of England and Wales.
The 1m DTM LIDAR analysis gives the hill the
following details:
Name: Gribin
Summit Height: 209.3m
Summit Grid Reference:
SH 67559 16814
Bwlch Height: 169.7m
Bwlch Grid Reference:
SH 67588 16670
Drop: 39.6m
LIDAR image of Gribin |
Therefore, the 209.3m LIDAR analysis for the
summit position at SH 67559 16814 and the 169.7m LIDAR analysis for
the bwlch position at SH 67588 16670 gives this hill 39.6m of drop, which
confirms its reclassification to 200m
Twmpau status.
The full details for the hill are:
Group: Cadair Idris
Name: Gribin
OS 1:50,000 map: 124
Summit Height: 209.3m
(LIDAR)
Summit Grid
Reference: SH 67559 16814 (LIDAR)
Bwlch
Height: 169.7m (LIDAR)
Bwlch Grid
Reference: SH 67588 16670 (LIDAR)
Drop: 39.6m (LIDAR)
Myrddyn Phillips (May 2018)
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