Change
Register
The
Welsh 500m P15s
Double
Subs
All
hills in Wales at or above 500m in height with a minimum prominence of 15m;
from the 500m summit of Esgair Saeson to the 1085m summit of Yr Wyddfa
‘The Welsh 500m P15s’ is a hill list co-authored by Myrddyn
Phillips and Aled Williams, and was first announced on the Mapping Mountains
site on 4th November 2015 where a complete breakdown of hill totals
was listed by Group. The list then
comprised of 630 hills within the main list that met the qualifying criteria
with over 100 of these hills making their first known appearance in any form of
hill list; emphasising the fact that this listing is the most comprehensive of
its kind for this height band of hill in Wales.
The listing originated in 2004 at which time it included a
sub category for those hills that met the qualifying height but only had 14m or
more and below 15m of drop, these are now known as the 500m Subs. This listing now
includes two other sub categories; the 490m
Subs and the Double Subs and this
Change Register details those hills that are, or have been listed within the Double Subs category.
The Double Subs are
those hills that fail to meet the Welsh
500m P15 qualification by less than 10m of height and also less than 1m of
drop, these are the hills that are 490m or more and below 500m in height and
have 14m or more and below 15m of drop.
The Double Subs first
appeared as a category of hill in the November 2015 announcement of the list on
Mapping Mountains, and when the totals for each category were given there were five
hills listed that met the qualification for Double
Subs, all of these hills were identified leading up to this announcement.
Since ‘The Welsh 500m
P15s’ listing originated it has
developed ever since with it now being co-authored with Aled Williams, having
the two other sub categories within it, and having over 330 marginal hills
surveyed using a basic levelling technique.
It is now also benefiting from the accurate surveys conducted with GPS /
GNSS receiver, an expanded range of Ordnance Survey maps available online and
most recently, by analysis of LIDAR data.
However, it is not just numerical data that has seen this
list develop since its first inception, it is also place-name data, and it was
because of this and their mutual interest in hill lists that the authors first
corresponded.
In recent years, acronyms or short monikers referring to
specific hill lists have become increasingly popular in hill-walking circles,
and during the compilation of ‘The Welsh
500m P15s’ the authors have used the Welsh word ‘Uchaf (Higher)’ to refer
to these hills, with the plural being ‘Uchafion’, since these summits take in
the higher tier of the Welsh uplands.
This moniker will be used on the Mapping Mountains site to refer to this
class of hill.
It seems fitting that the list of ‘The Welsh 500m P15s – Double Subs’ should now benefit from a detailed Change Register, and although
the hill list in its entirety is not yet published it is prudent for this
Change Register to initially detail the changes to this sub category since the
November 2015 introduction published on the Mapping Mountains site.
The Change Register to ‘The
Welsh 500m P15s – Double Subs’ appears
below with the reclassifications to the Double
Subs list being detailed chronologically in receding order.
Change
Register
The
Welsh 500m P15s (Yr Uchafion) – Double Subs
Banc yr Ŵyn 491m at SN 77182
92335
This hill’s deletion from the ranks of Double Sub-Uchafion was announced on Mapping Mountains on 11.05.17,
with the hill previously listed with c 14m of drop based on the 491m summit
spot height on the Ordnance Survey enlarged mapping hosted on the Geograph
website and an estimated bwlch height of c 477m based on bwlch contouring
between 470m – 480m. Its subsequent
deletion as a Double Sub-Uchaf is due
to LIDAR data analysed by Aled Williams, resulting in the hill having a bwlch
height of 478.1m and with no coverage of the summit position by LIDAR data the
summit spot height is being used in conjunction with the bwlch data from
LIDAR. The resulting 13m of drop is insufficient
for it to retain its Double Sub-Uchaf
status. Double Sub-Uchaf total decreases by one and confirmed as 5.
Blaen yr Henbant 497.8m at SO 25412 21736
The addition of this hill to the ranks of Double Sub-Uchaf was announced on the
Mapping Mountains site on the 16.04.17, with the hill previously considered not
classified and catalogued with only 12m of drop based on its 498m summit spot
height on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps
and the 486m bwlch spot height that appears on the Ordnance Survey enlarged
mapping hosted on the Geograph website. Its
inclusion as a Double Sub-Uchaf is
due to LIDAR data analysed by Aled Williams, resulting in the hill having a 497.8m
(converted to OSGM15) summit and 483.0m (converted to OSGM15) bwlch height,
with these values giving this hill 14.8m of drop which along with its summit
height is sufficient for it to be classified as a Double Sub-Uchaf. Double Sub-Uchaf total increases by one
and confirmed as 6.
Fowler’s Arm Chair 489.5m at SO 04122 79426
This hill’s deletion from the ranks of Double Sub-Uchaf was announced on the Mapping Mountains site on the
25.03.17, with the hill previously listed with an estimated summit height of c
491m based on the dimension of the uppermost 490m ring contour on Ordnance
Survey maps, and with a 477m bwlch height taken from the Ordnance Survey enlarged
mapping hosted on the Geograph website, with these values giving the hill an
estimated c 14m of drop, which was sufficient for it to be classified as a Double Sub-Uchaf. Its deletion from this category of sub hill
is due to LIDAR data analysed by Aled Williams, resulting in the hill having a
489.5m summit and 476.4m bwlch height, with these values giving this hill 13.1m
of drop which along with its summit height is insufficient for it to retain its
Double Sub-Uchaf status. Double
Sub-Uchaf total decreases by one and confirmed as 5.
Twynau Gwynion 496.2m at SO 06765 10699
The reclassification of this hill was announced on Mapping Mountains on 10.01.17, with the hill previously listed as a 490m Sub-Uchaf with 16m of drop based on
the 498m summit spot height on the Ordnance Survey 1:50,000 Landranger and
1:25,000 Explorer maps, and a 482m bwlch spot height on the Ordnance Survey
enlarged mapping hosted on the Geograph website. This hill was reclassified from a 490m Sub-Uchaf to a Double Sub-Uchaf from LIDAR data analysed by Aled Williams,
resulting in the hill having a 496.2m summit and 481.3m bwlch height, with
these values giving this hill 14.9m of drop which qualifies it for Double Sub-Uchaf status. Double Sub-Uchaf
total increases by one and confirmed as 6.
4th
November 2015 – Mapping Mountains first publishes details to ‘The Welsh 500m P15s – Double Subs’.
Double Subs
total
confirmed as 5.
Myrddyn Phillips and Aled Williams (January 2017)
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