Ash Tip (ST 031 663)
There has been a Significant Height Revision to a
hill that is now listed in the 30-99m
Twmpau and 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.
 |
| LIDAR image of Ash Tip (ST 031 663) |
The criteria for the two listings that this height revision
applies to are:
30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum
drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all
Welsh hills at or above 30m and below 100m in height with 20m or more and below
30m of drop, with the word Twmpau
being an acronym standing for thirty
welsh metre prominences and upward.
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, with
the Introduction to the Mapping Mountains publication of this list appearing on
the 3rd December 2015.
The name the hill is now listed by is Ash Tip and
this was derived from local enquiry, and it is adjoined to the Bro Morgannwg
group of hills, which are situated in the southern part of South Wales (Region
C, Sub-Region C2), and it forms a part of landscaped ground that once made up the
Aberthaw quarry and lime works, and it is positioned with the B4265 road to its
north, and has the small community of Sain Tathan (St Athan) towards the
north-west.
When the original 30-99m height band of Welsh P30
hills were published on Geoff Crowder’s v-g.me website this hill was not included
in either the main P30 list or the Hills
to be surveyed sub list, as
contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps of
the day showed the area that now makes up this hill as having no ring contours
of note.
 |
| Extract from the Ordnance Survey 1:25,000 Explorer map |
This area was 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 and for the
majority of land comprising old mine workings it shows present day contours, as
opposed to the blank space showed on the counterparts of the 1:50,000 Landranger
and 1:25,000 Explorer maps.
 |
| 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.
The summit height produced by LIDAR analysis is 50.0m
and as there are no contours of any significance on contemporary Ordnance
Survey 1:50,000 Landranger and 1:25,000 Explorer maps, this height comes within
the parameters of the Significant Height Revisions used within this page
heading, these parameters are:
The term Significant Height Revisions applies to
any listed hill whose interpolated height and Ordnance Survey or Harvey map
summit spot height has a 2m or more discrepancy when compared to the survey
result produced by the Trimble GeoXH 6000 or analysis of data produced via
LIDAR, also included are hills whose summit map data is missing an uppermost
ring contour when compared to the data produced by the Trimble or by LIDAR
analysis.
Therefore, this hill’s new listed summit height is
50.0m and this was derived from LIDAR analysis, this is 40m higher than the uppermost
10m ring contour on contemporary Ordnance Survey 1:50,000 Landranger and
1:25,000 Explorer maps.
The full details for the hill are:
Group: Bro Morgannwg
Name: Ash Tip
OS 1:50,000 map: 170
Summit Height (New Height):
50.0m (LIDAR)
Summit Grid Reference:
ST
03170 66338 (LIDAR)
Bwlch Height:
12.4m (LIDAR)
Bwlch Grid Reference:
ST 03298 66735 (LIDAR)
Drop: 37.6m (LIDAR)
Dominance: 75.20%
(LIDAR)
Myrddyn Phillips (November 2019)
No comments:
Post a Comment