Monday 2 June 2014

Hill Lists – Cymru / Wales – 200m Twmpau updates – Bryniau Clwyd



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 eighth Group is Bryniau Clwyd.



Bryniau Clwyd 
North from the Afon Dyfrdwy (River Dee) and the border with England at SJ 317 395 to SJ 066 429 and then south and west of the Afon Camddwr to the Fish Pond at Y Rug (SJ 056 438), continuing west of the Afon Camddwr to bwlch at SJ 069 477 and the Afon Clwyd at SJ 071 500 to the sea at SJ 997 808.  Bordering with Y Berwyn to the south, Mynydd Hiraethog to the west, the sea to the north and the English border to the east. 


Twmpau - 200m updates

Billins    294m    SJ 195 719

This hill is part of Halkyn Mountain and is a promotion from the sub-list as the hill has a summit triangulation pillar with a flush bracket height of 294.281m (293.981m to base of trig approximately) and a bwlch estimated as c 263m with contours between c 260m – c 265, giving the hill c 31m of drop.  There are two options for the position of the bwlch, both are estimated as c 263m high, they are situated at SJ 203 708 and SJ 208 700.



Pen y Ball    258m    SJ 173 756

This hill was not included in the original 200m P30 list.  The bwlch contouring is between c 225m – c 230m with the height estimated as c 227m, giving a drop of c 31m.  However, the summit consists of a mound that overlooks Holywell and has a monument on it that commemorates the marriage, coronation and silver jubilee of George V.  I do not know if the mound is man-made, if it is, it would exclude this hill from the P30 list as the drop would then be insufficient to qualify.



Coed Pen-y-gelli    233m    SJ 135 762

A promotion from the sub-list and a summit that is twinned with Coed Moel-dda at SJ 143 754, both summits are given a 233m black spot height on the Ordnance Survey 1:25,000 map.  The bwlch contouring for Coed Pen-y-gelli is between c 200m – c 205m and has been estimated as c 203m, giving a drop of c 30m.  The bwlch separating the twin summits has been estimated as c 218m, giving the non-prioritised summit of Coed Moel-dda a drop of c 15m.



Pt. 213m    213m    SJ 304 530

This is a summit relocation from the 211m hill previously listed by the invented name of Moss Hill at SJ 301537.  The new summit has a 213m spot height on the Ordnance Surveyed enlarged Geograph map.  The point notation has been used for its name as no appropriate name is known for the hill.




Sub-Twmpau - 200m updates

Moel Ffagnallt    289m    SJ 189 700

A hill that has recently been surveyed with the Trimble GeoXH 6000, the Ordnance Survey map has a summit spot height of 287m and the bwlch contouring is between c 260m – c 265m.



Pt. 257m    257m    SJ 096 720

This hill has a summit spot height of 257m on the Ordnance Survey enlarged Geograph map and bwlch contouring between c 230m – c 235m, with an estimated height of c 233m, giving a drop of c 24m.  There is also an adjacent ‘Mound’ that has an uppermost ring contour of c 255m at SJ 096 719.



Pt. 208m    208m    SJ 159 728

With a summit spot height of 208m and an estimated bwlch height of c 184m this hill qualifies for the Sub list with c 24m of drop.



Craig y Rhos    299m    SJ 149 435

The bwlch is placed at SJ 149 437 and has a 276m spot height on the Ordnance Survey enlarged Geograph map, giving this hill 23m of drop.



Pt. c 285m    c 285    SJ 206 703

With an estimated summit height of c 285m and an estimated bwlch height of c 263m, with bwlch contouring between c 260m – c 265m, this hill has an estimated c 22m of drop.



Pt. 214m    214m    SJ 152 737

The name of Bryn Glas appears close to the summit of this hill on Ordnance Survey maps but it is probably the name of the farm to the south-east of this hill’s summit, therefore the point notation has been used for the name of the hill.  The hill has a summit triangulation pillar with a flush bracket height of 214.344m in the OS Trig Database.  The bwlch contouring is between c 190m – c 195m, with an estimated height of c 192m, giving a drop of c 22m.



Pt. 295m    295m    SJ 088 469

With a summit height of 295m and an estimated bwlch height of c 274m at SJ 091 472, this hill is a new addition to the Sub list with an estimated c 21m of drop.



Bryn Digrif    217m    SJ 126 792

This hill has a summit spot height of 217m and a bwlch spot height of 196m at SJ 129 788, giving the hill 21m of drop.



Pt. 267m    267m    SJ 090 463

The bwlch contouring for this hill is centred on SJ 092 466 and is between c 240m – c 250m, with an estimated height of c 247m, giving a drop of c 20m.



Glol    232m    SJ 120 781

The Ordnance Survey enlarged Geograph map has a 212m spot height at SJ 172 782 which is at a road junction.  Although not centred on the valley to valey traverse the estimated bwlch height would be c 212m at SJ 128 781.  Therefore the hill enters the Sub list with a drop of c 20m.



Next update due on the 9th June 2014

No comments: