Monday 15 September 2014

Hill Lists – Cymru / Wales – 200m Twmpau updates – Mynydd Bach



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 Twenty Third Group is Mynydd Bach.



Mynydd Bach 

Initially east, then north and finally west of the Afon Teifi from SN 158 492 to Cors Caron at SN 677 622, continuing west of the Camddwr to bwlch at SN 645 687 and west and then south of the Afon Wyre to SN 527 699.  Bordering with the Elenydd to the north, east and south, and Moelfre and Mynydd Preseli to the south and the sea to the west.



Twmpau - 200m updates

Blaen Wern Wood    c 226m    SN 564 484

This hill is a summit relocation and a promotion from the Sub-List, as its previously listed 224m summit was positioned at SN 550 487 and appeared in the Sub-List under the part invented name of Allt Ty-llwyd.  The advent of the Ordnance Survey enlarged Geograph map now gives us 5m contour intervals for this area and with an uppermost c 225m contour Blaen Wern Wood replaces the hill at SN 550 487.  The summit height has been estimated as c 226m and the bwlch as c 194m, the latter based on bwlch contouring between c 190m – c 195m.  These values give this hill c 32m of drop.



Sub-Twmpau - 200m updates

Moel Rhydeinon    290m    SN 427 542

The height of this hill appears as 289m on Ordnance Survey maps, this height is given to a trig pillar.  The OS Trig Database gives a height of 290.254m adjoined to the flush bracket on the trig, as flush brackets are usually positioned 0.30m – 0.35m above the ground, the base of the trig would be at 289.904m – 289.954m, therefore this height has been rounded up to 290m for the purposes of this list.  The notes in the OS Trig Database state ‘station moved by farmer, B/Bolt poss. OK’.  If the height quoted is not to a flush bracket it may be to a bolt.  The bwlch is positioned at SN 407 527 with contouring between c 260m – c 265m, and has been estimated as being c 262m high.  These values give this hill c 28m of drop.



Pt. 234m    234m    SN 498 481

Another hill name that follows the Pt notation as no appropriate name is known for it by the blog author.  This hill has a 208m spot height on the area of its bwlch that appears on the Ordnance Survey enlarged Geograph map, giving this hill 26m of drop.



Pt. 271m    271m    SN 375 467

This hill qualifies for the Sub-List as it has a 246m spot height on the area of its bwlch that appears on the Ordnance Survey enlarged Geograph map.  Its name follows the Pt. notation as the blog author does not know an appropriate name for it, and it is one of many that do so in the Welsh 200m Sub-P30 List.  The summit value of 271m and bwlch value of 246m gives this hill 25m of drop.



Pt. 292m    292m    SN 404 519

The summit of this hill has a 292m spot height on it and its name takes on the customary Pt. notation as no appropriate name is known for it by the blog author.  The bwlch contouring is between c 265m – c 270m and has been estimated as c 267m high.  There are two spot heights that appear in the area of the bwlch on Ordnance Survey maps, the first is placed at a road junction at SN 396 518, this 268m spot height is considered to be placed too high for the critical bwlch position.  The second spot height is 266m and is placed at a road junction and appears on the Ordnance Survey enlarged Geograph map at SN 397 520, although near to where interpolation suggests the critical bwlch to be placed it is considered slightly too low.  The 292m summit and c 267m bwlch values give this hill c 25m of drop.



Pt. 289m    289m    SN 417 535

The 289m summit spot height appears near to where a Covered Reservoir is placed on the Ordnance Survey map.  If this height was to the top of the covered reservoir the height would likely have to decrease for this list, as covered reservoirs are considered modern mad-made objects and do not count for the height of a hill under the parameters of this list.  The name of this hill is another that follows the Pt. notation as no suitable name is known for it by the blog author.  Bwlch contouring is between c 260m – c 265m and the height is estimated as c 264m at SN 424 536.  The Ordnance Survey enlarged Geograph map has a 262m spot height near to a centralised bwlch location at SN 425 535, but this is considered too low for the critical bwlch position.  The 289m summit and c 264m bwlch values give this hill c 25m of drop.



Pt. 237m    237m    SN 574 557

The name of this hill follows the Pt. notation which is considered appropriate as no suitable name is known for the hill by the blog author.  The bwlch contouring is between c 210m – c 215m and the height of the bwlch is estimated as c 212m, giving this hill c 25m of drop.  There is a 211m spot height at SN 570 557 on Ordnance Survey maps, as the placement of this spot height is down steam of a Spring it is considered not to be at the point of the critical bwlch.



Allt Gelligarneddau    256m    SN 606 556

This hill qualifies for the Sub-List as it has an estimated bwlch height of c 232m, based on bwlch contouring between c 230m – c 240m, giving this hill c 24m of drop.  The next nearest higher summit is to the south of this hill at SN 611 542 and is reliant on being higher due to a 257m spot height appearing on the Ordnance Survey 1:50,000 map.



Allt Cwm-hyar    266m    SN 383 451 / SN 381 455

A Twin Top as there are two points with a 266m summit spot height, between the two summits is a 264m spot height that appears on the Ordnance Survey enlarged Geograph map at SN 381 454.  The bwlch has a 243m spot height on it at SN 379 463, giving this hill 23m of drop.



Banc y Carnau    239m    SN 523 594

This hill qualifies for the Sub-List as it has a 239m summit spot height and a 216m bwlch spot height, giving this hill 23m of drop.  The bwlch spot height is positioned at SN 524 592 and appears on the Ordnance Survey enlarged Geograph map.



Castell Goetre    235m    SN 602 509

Another hill whose qualification in the Sub-List is partly dependent upon the Ordnance Survey enlarged Geograph map, as this map gives a 212m spot height on the area of the bwlch, giving this hill 23m of drop.



Pt. 259m    259m    SN 662 650

Another hill whose listed name follows the Pt. notation as the blog author does not know an appropriate name for it.  The height of the bwlch has been estimated as c 236m, based on bwlch contouring between c 230m – c 240m, giving this hill c 23m of drop.



Pt. 248m    248m    SN 644 633

This hill’s qualification in to the Sub-List is reliant upon the Ordnance Survey enlarged Geograph map as it shows a summit spot height of 248m, whereas other current maps only have an uppermost c 240m contour ring.  The bwlch contouring is between c 220m – c 230m and the height of the bwlch has been estimated as c 225m, giving this hill c 23m of drop.



Pt. 268m    268m    SN 431 483

The listed name of this hill follows the Pt. notation as no suitable name is known for it by the blog author.  The area of the bwlch has a 246m spot height at SN 436 494 appearing on the Ordnance Survey enlarged Geograph map, giving this hill 22m of drop.



Pt. c 256m    c 256m    SN 555 542

Another hill whose name follows the Pt. notation as the blog author does not know an appropriate name for it.  Both summit and bwlch heights have been estimated, the former from an uppermost c 255m contour ring and the latter from contouring between c 230m – c 235m, with an estimated bwlch height of c 234m, giving this hill a drop of c 22m.



Pt. 224m    224m    SN 580 526

This hill qualifies for the Sub-List as it has a summit spot height of 224m and a bwlch spot height of 203m, giving this hill a drop of 21m.  The bwlch spot height appears on the Ordnance Survey enlarged Geograoh map at SN 570 546.  This hill is also another example where the Pt. notation is being used for the listed name as the blog author does not know an appropriate name for it.



Crug y Balog    244m    SN 342 452

The summit spot height for this hill appears on the Ordnance Survey 1:25,000 map, the bwlch contouring is between c 220m – c 225m and has been estimated as c 223m high, giving this hill a drop of c 21m.  The Ordnance Survey 1:50,000 map also has a 223m spot height at SN 345 457 on the area of the bwlch.  However, this may be misplaced as its position appears higher than the c 225m contour when the map is enlarged on the Geograph mapping available on its website.



Allt Hoffnant    239m    SN 326 523

This hill qualifies for the Sub-List as it has a 239m summit spot height and a 219m bwlch spot height positioned at SN 332 516, giving the hill 20m of drop.  This hill also has a Twin Top at SN 326 509 which is regarded as the prioritised summit and which qualifies for the main list of P30 hills with 45m of drop, with its 194m bwlch positioned at SN 339 522.



Pt. 224m    224m    SN 524 514

This hill name follows the Pt. notation as the blog author does not know a suitable name for it.  The hill qualifies for the Sub-List as it has a 224m summit spot height and a 204m bwlch spot height, giving the hill 20m of drop.



Pt. 295m    295m    SN 561 600

This is another example where the hill name follows the Pt. notation as no appropriate name is known for it by the blog author.  The contouring for this area is at 5m intervals on the Ordnance Survey enlarged Geograph map, the position of the bwlch is placed at SN 558 602 where two minor roads meet.  Unfortunately the c 275m contour on the Geograph map goes in to each road but does not continue out of them; therefore it is difficult to tell if the bwlch contouring is between c 270m – c 275m or between c 275m – c 280m.  For the purposes of this list I’m estimating the height of the bwlch as c 275m, giving this hill a drop of c 20m.

Next update due on the 22nd September 2014


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