Crasty Frain (SO 109
983)
There has been a Summit Relocation to a hill that
is listed in the 200m Twmpau, with the summit height, bwlch height
and their locations, the drop and status of the hill initially confirmed by
LIDAR analysis instigated by Joe Nuttall who produced a summit analysis
programme, and then by LIDAR analysis conducted initially by Jim Bloomer and
subsequently by Myrddyn Phillips, with the summit later surveyed with the
Trimble GeoXH 6000 and which was conducted by Myrddyn Phillips.
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| Crasty Frain (SO 109 983) |
The criteria for the list that this summit
relocation applies to are:
200m Twmpau – Welsh hills at or above
200m and below 300m in height that have 30m minimum drop, with an accompanying
sub category entitled the 200m Sub-Twmpau consisting of all Welsh hills at or
above 200m and below 300m in height that have 20m or more and below 30m of
drop. With the word Twmpau being an
acronym standing for thirty welsh metre prominences and upward.
 |
| The 200m Twmpau by Myrddyn Phillips |
The name the hill is now listed
by is Crasty Frain and this was derived from the Tithe map, and it is adjoined
to the Carnedd Wen group of hills which are situated
in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is
positioned with a minor road to its north and the B4389 road to its south-west,
and has the village of Tregynon towards the west north-west.
When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included
in the accompanying Hills to be surveyed
sub list, as it was considered not to meet the criteria then used for the main
P30 list, with its summit listed at SO 107 981 which compliments the position
of the 253m spot height that appears on the Ordnance Survey 1:25,000 Explorer
map.
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| Extract from the Ordnance Survey 1:25,000 Explorer map |
When the sub list was standardised, and
interpolated heights and drop values also included the details for this hill
were re-assessed and it was listed with an estimated c 27m of drop, based on
the 253m summit spot height that appears on the Ordnance Survey 1:25,000
Explorer map and an estimated c 226m bwlch height, with the latter based on
interpolation of 10m contouring between 220m – 230m.
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 relocation of this hill was initiated by Joe Nuttall who produced a summit analysis programme that used LIDAR with an alternative height map (DEM) allowing identification of summits and cols and thereby drops. The resulting spreadsheet
that Joe produced contains over 29,600 hills.
 |
| LIDAR image of Crasty Frain |
This spreadsheet is being evaluated by a number of
people, and for this particular hill it was Jim Bloomer who initially assessed
this hill’s data against that produced via LIDAR. Myrddyn Phillips then evaluated the details
for this hill via LIDAR analysis and confirmed its summit height and position and
hence its relocation and reclassification to 200m Twmpau status. The
summit of this hill has now been surveyed with the Trimble GeoXH 6000 and it is
this evaluation on the hill and the subsequent survey that is being
prioritised.
 |
| LIDAR summit image of Crasty Frain |
The summit height and position produced by the
Trimble GeoXH 6000 survey is 256.3m at SO 10995 98318, and this position in
relation to that previously given comes within the parameters of the Summit
Relocations used within this page heading, these parameters are:
The term Summit Relocations applies when the
hill’s high point is in a different field, or where a number of potential
summit positions are within close proximity and the highest point is not where
previously given, or when it is positioned to a different feature such as in a
conifer plantation, or when the high point of the hill is placed within a
different map contour, or 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 that is judged to be a relatively recent man-made construct, 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 new listed
summit height for this hill is 256.3m and is positioned at SO 10995 98318, this
position is not given a spot height on contemporary Ordnance Survey 1:50,000
Landranger and 1:25,000 Explorer maps but compliments the height and position
of the 256m spot height that appears on the mapping available on the Magic Maps
and the WalkLakes websites, and is approximately 250 metres north-westward from
where the previously listed summit is positioned.
The full details for the hill are:
Group: Carnedd Wen
Name: Crasty Frain
OS 1:50,000 map: 136
Summit Height: 256.3m
(converted to OSGM15, Trimble GeoXH 6000)
Summit Grid Reference (new position): SO 10995 98318 (Trimble GeoXH 6000)
Bwlch Height: 226.1m (LIDAR)
Bwlch Grid Reference:
SO 10787 98754 (LIDAR)
Drop: 30.2m (Trimble
GeoXH 6000 summit and LIDAR bwlch)
Myrddyn Phillips (October 2020)
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