Fan y Big (SO 036 206) – Hewitt reclassified to SubHewitt
This is one in a series of retrospective Hill
Reclassification posts that detail hills whose status has altered in the
listing of the Welsh Hewitts (an acronym for Hill in England, Wales or Ireland over Two Thousand feet high). These reclassification posts will give
details of hills where I have direct association with their change of status,
and they will tie in with a forthcoming Change Register giving detail to this
list and its alterations since first publication.
The listing of Welsh Hewitts was published in booklet format by TACit Tables in February 1997
and entitled The Hewitts and Marilyns of
Wales. This list evolved out of The
Absolute Summits of England and Wales which were known as the Sweats (an
acronym for Summits in Wales and England Above Two-thousand FEET) and which was
published by Cicerone Press in 1992 in the book entitled The Relative Hills of Britain.
The list compiler for the Hewitts and the preceding Sweats is Alan
Dawson.
When the Welsh Hewitts list was published in booklet format
there were 137 qualifying hills listed with their criteria being any Welsh hill
at or above 2000ft (609.6m) in height with 30m minimum drop, accompanying the
main list are two sub category’s entitled SubHewitts,
with the two sets of criteria being any Welsh hill at or above 600m and below
2000ft (609.6m) in height that have a minimum drop of 30m and any Welsh hill at
or above 2000ft (609.6m) in height with 20m or more and below 30m of drop.
 |
| The Hewitts and Marilyns of Wales by Alan Dawson |
The details for the hill reclassification appear below:
The name of the hill is Fan y Big, and it is adjoined to the Bannau
Brycheiniog group of hills, and it is positioned between the towns of
Aberhonddu (Brecon) to its north and Merthyr Tudful to its south.
 |
| Fan y Big (SO 036 206) |
Prior to this hill’s reclassification to SubHewitt status it was listed as a Hewitt with 30m of drop based on the 719m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 689m bwlch spot height that appears on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.
As the listed drop value of 30m is the minimum required for
Hewitt status it was prioritised for a GNSS survey. Prior to this survey taking place Aled
Williams analysed this hill with LIDAR data resulting in a 716.3m summit height
and a 688.1m bwlch height, with these values giving this hill 28.2m of drop.
 |
| LIDAR summit image of Fan y Big |
Subsequently the GNSS survey took place on the 30th June 2018 with a repeat summit survey taking place on the 21st August 2018. The hill was surveyed by Myrddyn Phillips using a Trimble GeoXH 6000 to determine the summit and bwlch height and also its drop value, resulting in the following:
1st summit survey 30.06.18: 716.800m
2nd summit survey 30.06.18: 716.676m
3rd summit survey 21.08.18: 716.754m
Bwlch survey 30.06.18:
688.2m
The average of the three summit surveys comes to 716.7m and
with a surveyed bwlch height of 688.2m, these values give this hill 28.5m of
drop, with all these details being forwarded to the list author.
 |
| The Trimble GeoXH 6000 gathering data at the summit of Fan y Big |
The reclassification of this hill from Hewitt to SubHewitt status was accepted by the list author and its new classification augmented in to the listing of the Hewitts in July 2018.
The full details for the hill are:
Name: Fan y Big
OS 1:50,000 map: 160
OS 1:25,000 map: 12
Summit Height: 716.7m
(converted to OSGM15, average of three summit surveys)
Summit Grid Reference:
SO 03654 20669 (as listed in the Hewitts)
Bwlch Height: 688.2m
(converted to OSGM15)
Bwlch Grid Reference:
SO 037 198 (as listed in the Hewitts)
Drop: 28.5m
Myrddyn Phillips (June 2019)
No comments:
Post a Comment