Monday, 3 November 2014

Hill Lists – Cymru / Wales – 200m Twmpau update - Bannau Brycheiniog

The first list to the Welsh 200m P30 hills was published on Geoff Crowder’s website in 2000; this list preceded the list of TuMPs by nine years, the list proved a very useful resource for the TuMP compilation for this category of hill.

The Welsh 200m P30 list documents all hills in Wales that are at or above 200m in height and are below 300m in height, to qualify for the main list each hill requires a minimum of 30m of prominence.

The hills listed below are updates to the Welsh 200m P30 list originally published on Geoff Crowder's website.  To see the original list click {here}

The original published list had a Sub-List which was entitled ‘Hills to Survey’.  This list consisted of all hills in Wales in the stipulated height band that have a minimum of 20m of prominence, but do not meet the minimum 30m of prominence to enter the main list, according to Ordnance Survey map spot heights and contours.  Nowadays the standard Sub-List takes in all hills that have a minimum of 20m of prominence.  However, the Hills to Survey Sub-List discounted hills whose map spot heights gave a drop value of less than 30m, but more than 20m.  By doing so, the only hills that were Sub-Listed were those that map values dictated stood a chance of entering the main list, for example; if a hill had a summit spot height of 250m and a bwlch spot height of 221m, it was not listed in the Hills to Survey Sub-List as with 29m of drop I thought it did not stand a chance of main list qualification.
When compiling the Sub-List I was measuring many hills for P30 status using a basic levelling technique, please click {here} for more information concerning this.  I now know that Ordnance Survey spot heights have a standard margin of uncertainty of + / - 3m associated with their accuracy.  Therefore many hills that were not listed in the original Sub-List may have sufficient drop to enter the main list.  Because of this the Sub-List has been altered to include all hills that have a minimum of 20m of drop but are not known to attain the minimum 30m of drop to enter the main list.

The hills listed below are those major amendments to the original Welsh 200m P30 list as it appears on Geoff’s website.  There are many hills that have been promoted from the Hills to Survey Sub-List to the main list, whilst there are many additions to the Sub-List now that it has been standardised to include all 20m minimum but below 30m drop hills.

When the 200m P30 list was first published it was the first to this category of hills and in some way it and its other 100m height band lists paved the way for Clem’s data that later appeared on the RHB file database and then for the TuMPs listing by Mark Jackson.

As well as the first P30 list to this height band the list is now the first to include a comprehensive Sub-List.

TuMP baggers beware; as the main list also includes P30’s not listed by Mark Jackson, so if you want to visit all P30’s you’ll have to include some non TuMPs to do so.

The list will be updated on a weekly basis and will be done so through each Group category, starting from the north and working south.  The Thirtieth Group is Bannau Brycheiniog.

Bannau Brycheiniog

West and then north from SO 242 154 following the River Clydach to bwlch at SO 192 115, and bwlch at SO 174 115, and bwlch at SO 147 115, and bwlch at SO 119 101, and bwlch at SO 082 086 towards the Nant Moriais to SO 046 062, continuing east of the Taf Fawr to the Llwyn-on Reservoir at SO 012 114 and from SO 004 128 to the Cantref Reservoir at SN 996 153 and from SN 992 163 to the Beacons Reservoir at SN 989 183 and the Blaen Taf Fawr from SN 986 190 to SN 987 194 and stream to bwlch at SN 982 203 and the Afon Tarell to SO 038 288, continuing south of the Afon Wysg (River Usk) to SO 242 154.  Bordering with Y Mynyddoedd Duon and Mynydd Epynt to the north, Fforest Fawr to the west, Bryniau Cymoedd to the south and Y Mynyddoedd Duon to the east. 

Twmpau - 200m updates

Cefn Cantref    293m    SO 048 269

This hill has been promoted from the Sub-List as the given drop is 30m, based on the hill having a twin 293m summit and a 263m spot height at the bwlch, with the latter appearing on the Ordnance Survey enlarged Geograph map.  The summit at SO 048 269 has a triangulation pillar on it with a flush bracket height of 293.223m, meaning ground at the immediate base of the trig is likely to be just under 293m high, but as ground adjacent to the base of the trig looks slightly higher the hill retains its twin summit status, for now!  The other summit is positioned at SO 049 262.

Next update due on the 10th November 2014

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