Cerrig y Ddinas (SH 754 739) – Sub-Trichant
reclassified to Trichant
There has been a reclassification to a hill that
is listed in the Y Trichant, with the
summit height and its position initially ascertained from LIDAR analysis and
the summit height, bwlch height and their locations, the drop and status of the
hill subsequently confirmed by a survey with the Trimble GeoXH 6000 conducted
by Myrddyn Phillips, with the latter taking place on the 22nd May
2019.
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| Cerrig y Ddinas (SH 754 739) |
The criteria for the list that this
reclassification applies to are:
Y Trichant – 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 of the hill is Cerrig y
Ddinas and it is adjoined to the Carneddau group of hills, which are situated
in the north-western part of North Wales (Region A, Sub-Region A1), and it is
positioned with the A55 road and the coast to its north, and has the town of
Conwy towards the north-east.
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
as it did not meet the criteria then used for the main P30 list; however the
main P30 and accompanying sub list has now been standardised and interpolated
heights and drop values also included.
When this list was standardised and interpolated
heights also included this hill was listed with an estimated c 26m of drop,
based on the 312m summit spot height that appears on the Ordnance Survey
1:25,000 Explorer map which was prioritised in favour of the 314m summit spot
height that appears on the Ordnance Survey 1:50,000 Landranger map, and an
estimated bwlch height of c 286m based on interpolation of 10m contouring on
the contemporary Ordnance Survey 1:25,000 Explorer map.
 |
| Extract from the Ordnance Survey 1:25,000 Explorer map |
 |
| Extract from the Ordnance Survey 1:50,000 Landranger map |
The details for this hill were re-examined when
the OS Maps website became available online.
This is the replacement for OS Get-a-map and has contours at 5m
intervals. The mapping on OS Maps shows
this hill with bwlch contouring between 280m – 285m with an estimated height of
c 284m giving this hill a drop value nearer 30m.
 |
| Extract from the OS Maps website |
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, however LIDAR coverage only takes in the summit of
this hill.
 |
| LIDAR summit image of Cerrig y Ddinas |
The reclassification of this hill to Trichant
status is due to a Trimble GeoXH 6000 bwlch and summit survey, resulting in a 313.5m
summit height and a 283.0m bwlch height, with these values giving this hill 30.5m
of drop, which is sufficient for this hill to be classified as a Trichant.
The full details for the hill are:
Group: Carneddau
Name: Cerrig y Ddinas
OS 1:50,000 map: 115
Summit Height: 313.5m
(converted to OSGM15)
Summit Grid Reference:
SH
75427 73948
Bwlch Height: 283.0m (converted to OSGM15)
Bwlch Grid Reference: SH 75140 73786
Drop: 30.5m (converted
to OSGM15)
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