Monday, 27 October 2014

Hill Lists – Cymru / Wales – 200m Twmpau update – Fforest Fawr

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 Twenty Ninth Group is Fforest Fawr.

Fforest Fawr

North from SO 030 076 following stream to bwlch at SO 005 073 and the Nant y Gwyddel to SN 988 046, continuing north of the Afon Cynon to bwlch at SN 942 062 and the Camnant and Sychryd to SN 910 079, and the Afon Mellte to SN 902 074, continuing north of the Afon Nedd (River Neath) to SN 898 091 and the Afon Pyrddin to bwlch at SN 844 107 and the Nant Llech to SN 834 127, continuing east of the Afon Tawe to SN 848 172 and the Nant Tywynni to bwlch at SN 870 195 and the Blaen-crai to the Cray Reservoir at SN 877 207, continuing east from SN 883 220 following the Afon Crai to SN 901 290, continuing south of the Afon Wysg (River Usk) to SO 038 288, continuing west of the Afon Tarell to bwlch at SN 982 203 and stream to SN 987 194 and the Blaen Taf Fawr to the Beacons Reservoir at SN 986 190, continuing west from SN 989 183 following the Taf Fawr to the Cantref Reservoir at SN 992 163 and from SN 996 153 to the Llwyn-on Reservoir at SO 004 128, continuing following the Taf Fawr from SO 012 114 to SO 030 076.  Bordering with Mynydd Epynt to the north, Y Mynydd Du to the west, Bryniau Cymoedd to the south and Bannau Brycheiniog to the east.  

Sub-Twmpau - 200m updates

Pt. 293m    293m    SN 941 290

The name of this hill follows the Pt. notation as the blog author does not know an appropriate name for it.  The summit has a 293m spot height on it, and bwlch contouring is between c 270m – c 280m, with the bwlch height estimated as c 273m high, these values give this hill c 20m of drop.

Next update due on the 3rd November 2014

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