Monday, 10 November 2014

Hill Lists – Cymru / Wales – 200m Twmpau updates – Coed Gwent

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 Thirty First Group is Coed Gwent.

Coed Gwent

East from the sea at ST 323 813 following the Afon Wysg (River Usk) to SO 359 092, continuing south of the Clawdd Brook to bwlch at SO 396 129, continuing east of the Nant y Deri to SO 401 146, continuing south of the Afon Troddi (River Trothy) to SO 515 116, continuing west of the Afon Gwy (River Wye) to the sea at ST 541 901.  Bordering with Y Mynyddoedd Duon to the north, Bryniau Cymoedd to the west, the sea to the south and the border with England to the east. 

Twmpau - 200m updates

Pt. 277m    277m    ST 485 990

This hill was always a prime candidate for promotion from the Sub-List as it has a 277m summit spot height, and bwlch contouring between c 245m – c 250m, with the height of the bwlch estimated as c 247m, giving this hill c 30m of drop.  The hill was originally listed under the part invented name of Devauden Hill; it now reverts to the Pt notation as the blog author does not know an appropriate name for it.

Pt. 232m    232m    SO 518 106

This hill has been promoted from the Sub-List as it has a summit spot height of 232m and an estimated bwlch height of c 202m, based on bwlch contouring between c 200m – c 205m, giving this hill c 30m of drop.  It was originally listed as Troypark Wood Top which was partly based on the name of the wood to the west of the summit, as this wood does not take in the high point the name has been amended to the Pt notation as the blog author does not know an appropriate name for it.  The name of Church Hill Common also appears on the lower south-easterly slope of this hill on Ordnance Survey maps, as this name may just apply to a piece of bounded land and not to the hill itself, it has not been used.

Sub-Twmpau - 200m updates

Trelleck Hill    c 288m    SO 506 064

This hill has an uppermost ring contour of c 285m and its height has been estimated as c 288m, the area of the bwlch has a 261m spot height on the Ordnance Survey enlarged Geograph map at SO 510 057, although the positioning of this spot height is not centred on the hill to hill traverse, contouring suggests it may be positioned near to the critical bwlch, therefore this hill enters the Sub-List with c 27m of drop.

Gaer Hill    264m    ST 516 981

Another hill whose drop value is dependent upon the Ordnance Survey enlarged Geograph map as both summit and bwlch are spot heighted.  The former has a 264m spot height and the latter a 239m spot height, giving this hill a drop of 25m.

Pt. 244m    244m    ST 435 974

This hill follows the Pt. notation for its name as no suitable name is known for it by the blog author.  The bwlch contouring is between c 220m – c 225m, with the height of the bwlch estimated as c 222m and placed at ST 433 972, giving this hill c 22m of drop.

Next update due on the 17th November 2014

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