Cae Rosser (SO 388 005) – Lesser Dominant
reclassified to Dominant
There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.
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| LIDAR image of Cae Rosser (SO 388 005) |
The criteria for the list that this
reclassification applies to are:
Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose
prominence equal or exceed half that of their absolute height. With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose
prominence is between one third and half that of their absolute height. The list is authored by Myrddyn Phillips with
the Introduction to the start of the Mapping Mountains publication of this list
appearing on the 3rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.
The name the hill is listed by is Cae Rosser and
this was derived from the Tithe map and it is adjoined to the Gwent Is Coed
group of hills which are situated in the
south-eastern part of South Wales (Region C, Sub-Region C3), and it is positioned with the A472 road to its north
and the A449 road to its east and the Afon Wysg (River Usk) to the west, and
has the town of Brynbuga (Usk) towards the north north-west.
When the original 30-99m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised and
interpolated heights and drop values also included, this hill was listed with c
33m of drop, based on an estimated c 70m summit height and an estimated c 37m
bwlch height, with each based on interpolation of 10m contouring that appears
on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.
 |
| 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 gave a 73m summit spot height
for this hill, which increased its estimated drop value to c 36m and a dominance
of 49.32%.
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 reclassification of this hill from
Lesser Dominant status is due to LIDAR analysis, resulting in a 72.7m summit
height and a 32.2m bwlch height, with these values giving this hill 40.5m of
drop and 55.68% dominance, which is sufficient for it to be classified as a
Dominant hill.
The full details for the hill are:
Group: Gwent Is Coed
Name: Cae Rosser
OS 1:50,000 map: 171
Summit Grid Reference:
SO
38857 00521 (LIDAR)
Summit Height: 72.7m
(LIDAR)
Bwlch Grid Reference:
SO 39355 00008 (LIDAR)
Drop Summit to Bwlch:
40.5m (LIDAR)
Drop Bwlch to ODN:
32.2m (LIDAR)
Dominance: 55.68% (LIDAR)
Myrddyn Phillips (July 2020)
