Pt. 183.5m (SN 375 052)
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%203.jpg) |
| LIDAR image of Pt. 183.5m (SO 375 052) |
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 hill is being listed by the point (Pt. 183.5m)
notation, and it is adjoined to the Ysgyryd Fawr group of hills, which are
situated in the south-eastern part of South
Wales (Region B, Sub-Region B4), and
it is positioned encircled by minor roads, with the B4598 road farther to its south-west,
and has the town of Brynbuga (Usk) towards the south.
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 16m of drop, based on
the 183m summit spot height positioned at SO 37555 05221 that appears on the
Ordnance Survey 1:25,000 Explorer map, and an estimated c 167m bwlch height,
based on interpolation of 5m contouring between 165m – 170m.
%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 183.7m positioned at SO 37563 05219.
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%201.jpg) |
| LIDAR summit image of Pt. 183.5m (SO 375 052) |
The height produced by LIDAR analysis to the natural
summit of this hill is 183.5m and is positioned at SO 37547 05248, 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 183.5m and
is positioned at SO
37547 05248, this position is not given a spot height on the contemporary
Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is
approximately 27 metres north-westward from the position of the previously
listed summit at the spot height, and approximately 29 metres north-westward
from where the high point of the raised field boundary is positioned.
The full details for the hill are:
Group: Ysgyryd Fawr
Name: Pt. 183.5m
OS 1:50,000 map: 161
Summit Height: 183.5m (LIDAR)
Summit Grid Reference (New Position): SO 37547 05248 (LIDAR)
Bwlch Height: 168.15m (LIDAR)
Bwlch Grid Reference: SO 37322 05167 (LIDAR)
Drop: 15.3m (LIDAR)
Myrddyn Phillips (May
2025)
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