Rhos Scythlyn (SN 430 361)
There has been a Summit Relocation to a hill that is listed in the The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips.
%20-%20LIDAR%20hill%201.jpg) |
| LIDAR image of Rhos Scythlyn (SN 430 361) |
The criteria for the list that this summit relocation applies
to are:
The Welsh
P15s – Welsh hills with 15m
minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s,
with the criteria for this sub category being all Welsh hills with 14m or more
and below 15m of drop. The list is authored by Myrddyn Phillips, with the
Introduction to the list appearing on Mapping Mountains on the 10th
May 2019.
 |
| The Welsh P15s by Myrddyn Phillips |
The name the hill is now listed by is Rhos
Scythlyn, and this was derived from the Tithe map, and it is adjoined to the
Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B,
Sub-Region B1), and it is positioned with
minor roads to its north-east, west and south, and the B4459 road to its east, and
has the town of Llandysul towards the north north-west.
When the listing that became known as The Welsh P15s was being compiled, this
hill was included in the main list with an estimated c 18m of drop, based on
the 256m summit spot height positioned at SN 43015 36148 that appears on the
Ordnance Survey 1:25,000 Explorer map, and an estimated c 238m bwlch height,
based on interpolation of 5m contouring between 235m – 240m.
%20-%201%2025000.jpg) |
| Extract from the Ordnance Survey 1:25,000 Explorer map |
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.
LIDAR analysis gives the highest ground on this
hill as 257.35m positioned at SN 42955 36082.
However, this is to the top of a raised field boundary and protocols
dictate that as this is deemed a relatively recent man-made construct such
ground is discounted from the height of a hill.
%20-%20LIDAR%20summit%202.jpg) |
| LIDAR summit image of Rhos Scythlyn (SN 430 361) |
The height produced by LIDAR analysis to the summit
of this hill is 257.0m and is positioned at SN 43043 36164, and this comes within the parameters of the Summit Relocations used
within this page heading, these parameters are:
The term Summit Relocations applies when the high
point of the hill is found to be positioned; in a different field, to a
different feature such as in a conifer plantation, within a different map contour either on Ordnance
Survey maps or interactive mapping, to a different point where a number of
potential summit positions are within close proximity, when natural ground or
the natural and intact summit of a hill is confirmed compared to a higher point
such as a raised field boundary or covered reservoir that is considered a
relatively recent man-made construct, or the de-twinning of a summit, or a
relocation of approximately 100 metres or more in distance from either the
position of a map spot height or from where the summit of the hill was previously
thought to exist.
Therefore, the summit
height produced by LIDAR analysis is 257.0m and
is positioned at SN
43043 36164, this position is not given a spot height on the contemporary
Ordnance Survey 1:25,000 Explorer map and is approximately 28 metres north-westward
from where the 256m spot height is positioned and approximately 90 metres north-westward
from the high point of the raised field boundary.
The full details for the hill are:
Group: Mynydd Pencarreg
Name: Rhos Scythlyn
OS 1:50,000 map: 146
Summit Height: 257.0m (LIDAR)
Summit Grid Reference (New Position): SN 43043 36164 (LIDAR)
Bwlch Height: 239.3m (LIDAR)
Bwlch Grid Reference: SN 41655 34356 (LIDAR)
Drop: 17.7m (LIDAR)
Myrddyn Phillips (May
2025)
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