Cae Alen (SH 781 758)
There has been a Summit Relocation to a hill that
is listed in the 100m Twmpau, with
the summit height, its location, the drop and status of the hill confirmed by
LIDAR analysis, and a subsequent summit survey with the Trimble GeoXH 6000
conducted by Myrddyn Phillips, with the latter taking place on the 10th
October 2018.
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| LIDAR image of Cae Alen and Bwlch Mawr |
The criteria for the list that this summit
relocation applies to are:
100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m
minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all
Welsh hills at or above 100m and below 200m 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.
The name of the bounded land where the summit of
this hill is situated is Cae Alen and this was derived from the Tithe map, and
it is this name that the hill is now listed by.
The hill 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 B5106 road to its west and the Afon Conwy (River
Conwy) to its east, and has the town of Conwy towards its north.
This summit relocation relates to two points, with
the north-easterly point given a 130m summit spot height positioned at SH 781
758 on contemporary Ordnance Survey maps, and the south-westerly point given a
small uppermost 130m ring contour positioned at SH 777 755.
When the origin 100m height band of Welsh P30
hills were published on Geoff Crowder’s v-g.me website, the north-easterly 130m
map heighted summit positioned at SH 781 758 was prioritised for P30 status over
that of the south-westerly point positioned at SH 777 755.
 |
| Extract from the Ordnance Survey 1:25,000 Explorer map |
The details for these hills were re-assessed when
the Ordnance Survey Vector Map Local became available online, this map is
hosted on the Geograph website and is entitled the Interactive Coverage Map,
and as an uppermost contour ring should be prioritised over that of a same map
heighted spot height the south-westerly point positioned at SH 777 755 was now prioritised
for P30 status over the north-easterly 130m spot heighted summit positioned at
SH 781 758.
It was not until LIDAR became available and
analysed that the details for these hills 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 image of Bwlch Mawr |
The height produced by LIDAR analysis and a
subsequent survey with the Trimble GeoXH 6000 confirmed the north-easterly summit
as higher:
North-easterly summit; Cae Alen: 129.1m at SH 78116 75814
South-westerly summit; Bwlch Mawr: 128.4m at SH 77790 75561
This comes within the parameters of the Summit
Relocations used within this page heading, these parameters are:
The term Summit Relocations applies to any listed
hill whose summit meets the following criteria; where there are a number of
potential summit positions within close proximity and the highest point is not
where previously given, 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, or when the summit of the hill is
in a different field compared to where previously given, or when the natural
and intact summit of a hill is confirmed compared to a higher point such as a
raised field boundary that is judged to be a relatively recent man-made
construct. As heights on different
scaled Ordnance Survey maps are not consistent the height given on the 1:25,000
Explorer map is being prioritised in favour of the 1:50,000 Landranger map for
detailing these relocations.
 |
| The Trimble GeoXH 6000 gathering data at the summit of Cae Alen |
 |
| The Trimble GeoXH 6000 gathering data at the summit of Bwlch Mawr |
Therefore the height produced by the Trimble GeoXH
6000 survey is 129.1m positioned at SH 78116 758124, this position is given a
130m spot height on contemporary Ordnance Survey maps and is approximately 400m
north-east from where the previously listed summit position is situated which
was surveyed as being 128.4m in height and positioned at SH 77790 75561.
The full details for the hill are:
Group: Carneddau
Name: Cae Alen
OS 1:50,000 map: 115
Summit Height: 129.1m (converted
to OSGM15)
Summit Grid Reference (new position): SH 78116 75814
Bwlch Height: 34.8m (LIDAR)
Bwlch Grid Reference:
SH 77629 74003 (LIDAR)
Drop: 94.3m (Trimble
summit and LIDAR bwlch)
Myrddyn Phillips (April 2019)
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