Monday 12 May 2014

Hill Lists – Cymru / Wales – 200m Twmpau updates – Rhinogydd



The first list to the Welsh 200m P30 hills was published on Geoff Crowder’s website v-g.me 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 fifth Group that has major updates is the Rhinogydd.



Rhinogydd
North and then west of the Afon Mawddach from SH 616 151 to SH 728 247, west of the Afon Eden to Llyn Trawsfynydd at SH 693 366, south of the Afon Prysor from SH 673 377 and south of the Afon Dwyryd at SH 653 397 to the sea at SH 617 379.  Bordering with the Moelwynion to the north, the Arennig to the east, Cadair Idris to the south and the sea to the west.


Sub-Twmpau - 200m updates


Pt. 215m    215m    SH 637 314

This hill is positioned just above the southern part of Llyn Cwm Bychan and has a 215m summit and 194m bwlch spot height on the large scale Ordnance Survey mapping on the Geograph website.  These values give this hill 21m of drop.


Pt. c 222m    c 222m    SH 649 382

This hill’s summit and bwlch height have been estimated from contour interpolation, with the summit estimated as c 222m high and the bwlch estimated as c 202m at SH 650 383, giving this hill c 20m of drop.



Next update due on the 19th May 2014

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