Wednesday, 11 January 2017

Change Register - The Welsh 500m P15s - 500m Subs


Change Register

The Welsh 500m P15s
500m Subs

All hills in Wales at or above 500m in height with a minimum prominence of 15m; from the 500m summit of Esgair Saeson to the 1085m summit of Yr Wyddfa


The Welsh 500m P15s is a hill list co-authored by Myrddyn Phillips and Aled Williams, and was first announced on the Mapping Mountains site on 4th November 2015 where a complete breakdown of hill totals was listed by Group.  The list then comprised of 630 hills within the main list that met the qualifying criteria with over 100 of these hills making their first known appearance in any form of hill list; emphasising the fact that this listing is the most comprehensive of its kind for this height band of hill in Wales.

The listing originated in 2004 at which time it included a sub hill category for those hills that met the qualifying height but only had 14m or more and below 15m of drop, these are now known as the 500m Subs.  Since the listing originated it has developed ever since with over 330 marginal hills having been surveyed using a basic levelling technique.  It is now benefiting from the accurate surveys conducted with GPS / GNSS receiver, an expanded range of Ordnance Survey maps available online and most recently, by analysis of LIDAR data.

However, it is not just numerical data that has seen this list develop since its first inception, it is also place-name data, and it was because of this and their mutual interest in hill lists that the authors first corresponded.

In recent years, acronyms or short monikers referring to specific hill lists have become increasingly popular in hill-walking circles, and during the compilation of ‘The Welsh 500m P15s’ the authors have used the Welsh word ‘Uchaf (Higher)’ to refer to these hills, with the plural being ‘Uchafion’, since these summits take in the higher tier of the Welsh uplands.  This moniker will be used on the Mapping Mountains site to refer to this class of hill.

It seems fitting that the list of ‘The Welsh 500m P15s – 500m Subs should now benefit from a detailed Change Register, and although the hill list in its entirety is not yet published it is prudent for this Change Register to initially detail the changes to this sub category since the November 2015 introduction published on the Mapping Mountains site.

The Change Register to ‘The Welsh 500m P15s – 500m Subs appears below with the reclassifications to the 500m Subs list being detailed chronologically in receding order.




Change Register

The Welsh 500m P15s (Yr Uchafion) – 500m Subs






Carreg yr Ast    579.3m at SN 87717 59184

This hill’s inclusion as a 500m Sub-Uchaf was announced via Mapping Mountains on the 19.07.17; prior to this the hill had not been classified.  Its addition to the 500m Sub-Uchaf ranks is due to analysis of LIDAR data by Aled Williams, with the resulting summit height of 579.3m (converted to OSGM15) and bwlch height of 564.3m (converted to OSGM15) being sufficient for 500m Sub-Uchaf status with the hill having 14.94m of drop.  500m Sub-Uchaf total increases by one and confirmed as 26.   





Banc Steffan    548.0m at SN 83359 70024

This hill’s deletion from 500m Sub-Uchaf status was announced on Mapping Mountains on the 21.05.17, with the hill previously listed in this sub category with 14m of drop based on a 46ft 6˝ (14.2m) basic levelling survey (BLS) conducted by Myrddyn Phillips on 08.08.05.  This BLS was conducted from the bwlch at SN 83371 70383 to the 549m map heighted summit of Cnapyn Drawsffos at SN 83443 70638, and as the Ordnance Survey also give a 549m spot height to Cefn Ffosyrewig at SN 83242 69234 the basic levelling survey meant that the lower of these two hills qualified as a 500m Sub-Uchaf with just over 14m of drop.  To complicate matters when the basic levelling survey was conducted the summit of Banc Steffan at SN 83359 70024 and which is situated between Cnapyn Drawsffos and Cefn Ffosyrewig was not given a spot height on maps of the day and had an uppermost 540m ring contour, therefore whichever summit out of the three is higher would qualify as an Uchaf and the higher of the other two lower summits would, according to the basic levelling survey, qualify as a 500m Sub-UchafThis hill’s subsequent deletion from 500m Sub-Uchaf status is due to analysis of LIDAR data by Aled Williams, with the resulting summit height of 548.0m and bwlch height of 534.2m being insufficient for this hill’s retention in this sub category with only 13.8m of drop.  500m Sub-Uchaf total decreases by one but remains as 25.  This figure remains at it was prior to this hill’s deletion as the hill was missed from this sub category when the Introduction to the list was published on Mapping Mountains in November 2015.
  




Pt. 522.0m    522.0m at SJ 13615 36369

The announcement of this hill’s deletion from the 500m Sub-Uchaf ranks was announced on Mapping Mountains on the 22.04.17, with the hill previously listed in this sub category with 14m of drop based on the 522m summit spot height on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and the 508m bwlch spot height on the Ordnance Survey 1:25,000 Explorer map.  This hill’s subsequent deletion from 500m Sub-Uchaf status is due to analysis of LIDAR data by Aled Williams, with the resulting summit height of 522.0m (converted to OSGM15) and bwlch height of 508.2m (converted to OSGM15) being insufficient for its retention in this sub category with only 13.8m of drop.  500m Sub-Uchaf total decreases by one and confirmed as 25.   





Pt. 524.0m    524.0m at SN 88113 16370

This hill’s inclusion as a 500m Sub-Uchaf was announced via Mapping Mountains on the 15.04.17; prior to this the hill had not been classified.  Its addition to the 500m Sub-Uchaf ranks is due to analysis of LIDAR data by Aled Williams, with the resulting summit height of 524.0m (converted to OSGM15) and bwlch height of 509.4m (converted to OSGM15) being sufficient for 500m Sub-Uchaf status with the hill having 14.6m of drop.  500m Sub-Uchaf total increases by one and confirmed as 26.   





Drum Boeth    523.4m at SH 72020 46289

Gathering data with the Trimble GeoXH 6000 at the summit of Drum Boeth (SH 720 462)

The announcement of this hill’s reclassification to Uchaf status was made on the Mapping Mountains site on the 01.04.17, with the hill previously listed as a 500m Sub-Uchaf based on a 48ft 6(14.8m) drop value produced by a basic levelling survey conducted by Myrddyn Phillips on the 27.10.05.  This hill’s reclassification from 500m Sub-Uchaf status is due to analysis of LIDAR data by Aled Williams, with the resulting summit height of 523.4m and bwlch height of 508.3m giving this hill sufficient drop to be included as an Uchaf, the hill has subsequently been surveyed with the Trimble GeoXH 6000 on 08.04.17 resulting in a 523.4m (converted to OSGM15) summit height and a 508.1m (converted to OSGM15) bwlch height, with these values giving this hill 15.2m of drop.  500m Sub-Uchaf total decreases by one and confirmed as 25.   





Cefn Cwm Coel    504m at SN 89101 64730

This hill’s reclassification to 500m Sub-Uchaf was announced Mapping Mountains on the 12.02.17, with the hill previously listed as an Uchaf with 15m of drop based on the Ordnance Survey 504m summit spot height on the 1:50,000 Landranger, 1:25,000 Explorer and on the enlarged mapping hosted on the Geograph website, with the latter map showing a 489m bwlch spot height.  This hill’s reclassification from an Uchaf to a 500m Sub-Uchaf is due to analysis of LIDAR bwlch data by Aled Williams, with the resulting height of 489.6m when combined with the 504m summit spot height only giving this hill 14m of drop, which is insufficient for continued Uchaf status.  500m Sub-Uchaf total increases by one and confirmed as 26.   





Cefn Onneu    530.0m at SO 17112 15692

The reclassification of this hill was announced on the Mapping Mountains site on 31.01.17, with the hill previously listed as an Uchaf with c 15m of drop based on an estimated summit height of c 530m and an estimated bwlch height of c 515m.  This hill has been reclassified from an Uchaf to a 500m Sub-Uchaf from LIDAR data analysed by Aled Williams, with the resulting heights being 530m summit and 515.6m bwlch, giving this hill 14.4m of drop which is insufficient to retain its Uchaf status.  500m Sub-Uchaf total increases by one and confirmed as 25.  





Pt. 637.1m    637.1m at SO 26709 32261

Pt. 637.1m (SO 267 322) is now reclassified to a 500m Sub-Uchaf

This reclassification was announced on the Mapping Mountains site on 30.11.16, with the hill previously listed as an Uchaf with c 15m of drop based on the 637m summit spot height on Ordnance Survey maps and an estimated bwlch height based on contour interpolation of c 622m.  This hill was reclassified from an Uchaf to a 500m Sub-Uchaf from LIDAR data analysed by Aled Williams, who had analysed this hill’s data independent of Joe Nuttall who was the first person to scrutinise this hill with LIDAR data, both found that the hill was given less than 15m of drop with Aled’s analysis producing a 637.4m summit and 622.7m bwlch height, with these values giving the hill only 14.7m of drop.  This hill has subsequently been surveyed with the Trimble GeoXH 6000 on the 28.09.17 resulting in a 637.1m summit height and a 622.5m bwlch height, with these values confirming that this hill has less than 15m of drop which is insufficient to retain its Uchaf status.  500m Sub-Uchaf total increases by one and confirmed as 24.  

   



Graig Fach    513.1m at SN 82140 93168

Graig Fach entered the ranks of Uchafion via a basic levelling survey and it has now been reclassified to the ranks of 500m Sub-Uchaf via a Trimble GeoXH 6000 survey

The first Uchaf to have been reclassified to a 500m Sub-Uchaf by surveying with the Trimble GeoXH 6000 since details of the list were made public in November 2015.  This status change was announced via the Mapping Mountains site on 21.05.16, the hill had been previously listed as an Uchaf based on the 514m summit spot height appearing on Ordnance Survey 1:25,000 Explorer maps coupled with a basic levelling survey conducted by Myrddyn Phillips on 22.05.04 resulting in 56ft 6(17.2m) of drop.  This hill was subsequently surveyed with the Trimble GeoXH 6000 by Myrddyn Phillips on 05.05.16, resulting in the hill having 14.5m of drop, which is insufficient for qualification as an Uchaf500m Sub-Uchaf total increases by one and confirmed as 23.




4th November 2015 – Mapping Mountains first publishes details to ‘The Welsh 500m P15s – 500m Subs

500m Sub-Uchaf total confirmed as 22.




Myrddyn Phillips and Aled Williams (January 2017)

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