Tuesday, 14 March 2017

Mapping Mountains – Hill Reclassifications – Y Pedwarau


Pt. 499.1m (SN 863 760) - 500m Sub-Pedwar reclassified to 400m Sub-Pedwar

There has been a reclassification to the listing of Y Pedwarau with a 500m Sub-Pedwar being reclassified to the ranks of 400m Sub-Pedwar by analysis of LIDAR data by Aled Williams.  The 400m Sub-Pedwarau is one of five categories of sub hills that accompany the main Y Pedwarau list, with the criteria for 400m Sub-Pedwar status being all Welsh hills at or above 400m and below 500m in height with 20m or more and below 30m of drop.

The hill is situated in the Elenydd group of hills with its Cardinal Hill being Draws Drum (SN 790 811) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B2).  The hill is situated with the small community of Llangurig to the north-east and Cwmystwyth to the west south-west and is positioned directly above and to the north of the narrow mountain road that heads north-westward from Rhaeadr Gwy (Rhayader).

As the hill is immediately above a road access to it is relatively easy from where a public footpath is indicated on Ordnance Survey maps leaving the road to the west south-west of the summit and following a stream valley up toward the hill’s west, from here the ascent to the featureless flat topped summit area is on ground that is relatively easy compared to other hills in the vicinity.

The sub category of 500m Sub-Pedwarau is relatively new having only been announced on the 30.01.17 when the Y Pedwarau started publication on the Mapping Mountains site, prior to this hill’s reclassification it had been listed as an Uchaf and a 500m Sub-Twmpau with 27.9m of drop and an estimated c 500m summit height based on the small 500m uppermost contour ring on Ordnance Survey maps and the flat topped nature of its summit area.

The name of the hill is currently being listed by the point (Pt. 499.1m) notation and its reclassification from 500m Sub-Pedwar to 400m Sub-Pedwar is due to analysis of LIDAR data by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:


Pt. 499.1m

Summit Height:  499.1m

Summit Grid Reference:  SN 86343 76073

Bwlch Height:  471.0m

Bwlch Grid Reference:  SN 86323 76358

Drop:  28.1m


Therefore, the 499.1m LIDAR data produced for the summit position at SN 86343 76073 and the 471.0m LIDAR data produced for the bwlch position at SN 86323 76358 gives this hill 28.1m of drop, which is in good accordance with the value produced for this hill when surveyed by John Barnard, Graham Jackson, David Purchase and myself in June 2008 using a level and staff resulting in a drop of 27.9m.  Therefore the summit height of this hill is insufficient for it to retain its 500m Sub-Pedwar status, and therefore it is reclassified to a 400m Sub-Pedwar with a 499.1m summit height and 27.9m of drop, and the list of Y Pedwarau will be updated accordingly.


The full details for the hill are:

Cardinal Hill:  Draws Drum

Summit Height:  499.1m (LIDAR data)

Name:  Pt. 499.1m

OS 1:50,000 map:  135, 136, 147

Summit Grid Reference:  SN 86343 76073  
 
Drop:  27.9m (line survey)


The hill will be taken out of the 500m Sub-Pedwar list and added to the 400m Sub-Pedwar list in forthcoming publications.  The list of Pedwar hills is available from the Haroldstreet website (January 2014) with all subsequent changes available via the Mapping Mountains site, with the list also having commenced publication on Mapping Mountains on the 30.01.17.

The list of additions and reclassifications from / to the 400m Sub-Pedwar list since the 1st edition of Y Pedwarau was published by Europeaklist are as follows:



400m SUB-PEDWAR ADDITIONS


















Pt. 499.1m (LIDAR data) (SN 863 760) 500m Sub-Pedwar reclassified to 400m Sub-Pedwar with 499.1m summit height





400m SUB-PEDWAR RECLASSIFICATIONS













400m SUB-PEDWAR DELETIONS










Myrddyn Phillips and Aled Williams (March 2017)






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