Disgwylfa (SN 982 663) – 400m Sub-Pedwar deletion
There has been a deletion to the listing of Y Pedwarau due to analysis of LIDAR data
by Aled Williams. Y Pedwarau is the title for the list of 400m hills of Wales and
takes in all Welsh hills at or above 400m and below 500m in height that have a
minimum 30m of drop, the list is a joint compilation between Myrddyn Phillips
and Aled Williams and it commenced publication on Mapping Mountains on the
30.01.17.
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| LIDAR image of Disgwylfa (SN 982 663) |
Accompanying the main Y Pedwarau list are five categories of sub hills, with this hill being deleted from the 400m Sub-Pedwar category. The criteria for 400m Sub-Pedwar qualification is all Welsh hills at or above 400m and below 500m in height with 20m or more and below 30m of drop.
Prior to analysis of LIDAR data the hill was
listed with 20m of drop based on the 477m summit spot height and the 457m bwlch
spot height that appear on the Ordnance Survey enlarged mapping hosted on the
Geograph website.
The hill is situated in the Hirddywel range with its
Cardinal Hill being Gwastedyn Hill (SN
986 661) and is placed in the Region
of Mid and West Wales (Region B, Sub-Region B1), and is positioned above the A
470 road which is to its north-west and has the town of Rhaeadr Gwy (Rhayader) to the north north-west.
As the summit of the hill is not a part of
designated open access land permission should be sought to visit, however
common sense should prevail as the summit is a local landmark and as the name
of the hill implies it is a look out position, and as open access land is close
to the high point to its immediate south, a visit to its summit should not
course any dispute.
The name of the hill is Disgwylfa, although the area of the summit is also named as a part
of Gwastedyn, and its deletion from
400m Sub-Pedwar status is due to the analysis of LIDAR data by
Aled Williams. LIDAR (Light Detection
& Ranging) is highly accurate height data that is now freely available for
much of England and Wales.
LIDAR analysis gives the hill the
following details:
Disgwylfa
Summit Height: 475.6m
Summit Grid Reference:
SN 98211 66311
Bwlch Height: 456.1m
Bwlch Grid Reference: SN 98422 66293
Drop: 19.5m
Therefore, the 475.6m LIDAR data produced for the summit
position at SN 98211 66311 and the 456.1m LIDAR data
produced for the bwlch position at SN 98422 66293 gives
this hill 19.5m of drop which is insufficient for its continued inclusion as a 400m Sub-Pedwar.
The full details for the hill are:
Cardinal Hill: Gwastedyn
Name: Disgwylfa
Summit Height: 475.6m (LIDAR)
Summit Grid Reference:
SN 98211 66311 (LIDAR)
Drop: 19.5m (LIDAR)
The total for Y
Pedwarau remains at 442 hills with nine additions, and fourteen
reclassifications to 400m Sub-Pedwar
status since publication of the list by Europeaklist in May 2013.
The overall total for the 400m
Sub-Pedwarau is now 218 with 25 hills being added and 20 hills being taken
out of this category since publication of the list by Europeaklist in May 2013.
The list of Pedwar
hills is available from the Haroldstreet website (January 2014) with all
subsequent changes detailed on the Mapping Mountains site, with the list also
having commenced publication on Mapping Mountains on the 30.01.17.
For the additions, reclassifications and deletions to Y Pedwarau reported on Mapping Mountains
since the May 2013 publication of the list by Europeaklist please consult the
following Change Registers:
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| Disgwylfa (SN 982 663) is now deleted from the 400m Sub-Pedwar category |
Myrddyn Phillips and Aled Williams (July 2017)
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