Monday, 28 July 2014

Hill Lists – Cymru / Wales – 200m Twmpau updates – Pegwn Mawr

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 sixteenth Group is Pegwn Mawr.

Pegwn Mawr 

North of the Rhyd-hir Brook at SN 974 677, the Black Brook and the Afon Dulas to SO 064 637, continuing north and then east of the Afon Ieithon (River Ithon) to SO 087 609 and then west of the Afon Ieithon (River Ithon) to SO 087 827, continuing west of the Camnant to bwlch at SO 070 842, following stream to SO 081 859 and the Cwm-y-rhiwdre Brook to Lake Mochdre and the Mochdre Brook to SO 085 906, continuing south of the Afon Hafren (River Severn) to SN 945 838, continuing east of the Afon Dulas to bwlch at SN 982 750 and the Afon Marteg to SN 951 714, continuing east of the Afon Gwy (River Wye) to SN 974 677.  Bordering with Carnedd Wen to the north, Beacon Hill and Fforest Glud to the east, Gwastedyn Hill to the south and the Elenydd, Garreg Lwyd and Pumlumon to the west.      

Sub-Twmpau - 200m updates

Pt. 239m    239m    SO 075 896

This hill has a 239m spot height on the area of the summit and a 212m spot height at the bwlch, the latter appears on the Ordnance Survey enlarged Geograph map.  These values give this hill 27m of drop.

Pt. 279m    279m    SO 094 677

The second update to the hills of Pegwn Mawr follows the Pt. notation as no appropriate name is known by the blog author for this hill.  The bwlch contouring is between c 250m – c 260m and has been estimated as c 252m, giving this hill a drop of c 27m.

Next update due on the 4th August 2014

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