Monday, 1 May 2017

Mapping Mountains – Hill Reclassifications – Y Pedwarau


Pt. 416.8m (SH 837 332) – 400m Sub-Pedwar addition

There has been an addition to the listing of Y Pedwarau due to analysis of LIDAR data by Aled Williams.  Y Pedwarau is the title for the list of 400m hills of Wales and takes in all Welsh hills at or above 400m and below 500m in height that have a minimum 30m of drop, the list is a joint compilation between Myrddyn Phillips and Aled Williams, and it commenced publication on Mapping Mountains on the 30.01.17.

Accompanying the main Y Pedwarau list are five categories of sub hills, with this addition affecting the 400m Sub-Pedwar category.  The criteria for 400m Sub-Pedwar qualification is all Welsh hills at or above 400m and below 500m in height with 20m or more and below 30m of drop.

Prior to analysis of LIDAR data the hill was categorised with 19m of drop based on the 417m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 398m bwlch spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The hill is situated in the Arenig group of hills with its Cardinal Hill being Arenig Fawr (SH 827 369) and is placed in the Region of North Wales (Region A, Sub-Region A3), and is positioned with the small community of Llanuwchllyn to its south-east.

If wanting to visit the hill permission to do so should be sought as it is not on open access land and to add to access problems the map indicates that its summit is immersed in conifer trees.  However, it is positioned between two public footpaths with the one to its west nearest to its summit.

The hill is being listed by the point (Pt. 416.8m) notation as the authors do not know a suitable name for it either from historical research or local enquiry and its addition to 400m Sub-Pedwar status is due to the 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. 416.8m

Summit Height:  416.8m (converted to OSGM15)

Summit Grid Reference:  SH 83743 33235

Bwlch Height:  396.7m (converted to OSGM15)

Bwlch Grid Reference:  SH 83569 33326

Drop:  20.1m


Therefore, the 416.8m (converted to OSGM15) LIDAR data produced for the summit position at SH 83743 33235 and the 396.7m (converted to OSGM15) LIDAR data produced for the bwlch position at SH 83569 33326 gives this hill 20.1m of drop which is sufficient for its inclusion as a 400m Sub-Pedwar.


The full details for the hill are:

Cardinal Hill:  Arenig Fawr

Summit Height:  416.8m (converted to OSGM15) (LIDAR data)

Name:  Pt. 416.8m

OS 1:50,000 map:  124, 125

Summit Grid Reference:  SH 83743 33235

Drop:  20.1m (converted to OSGM15) (LIDAR data)


The overall total for Y Pedwarau remains at 445 hills with eight additions, and ten reclassifications to 400m Sub-Pedwar status since publication of the list by Europeaklist in May 2013.

The overall total for the 400m Sub-Pedwarau is now 217 with 19 hills being added and 15 hills being taken out of this category since publication of the list by Europeaklist in May 2013.

The list of Pedwar hills is available from the Haroldstreet website (January 2014) with all subsequent changes detailed on the Mapping Mountains site, with the list also having commenced publication on Mapping Mountains on the 30.01.17.

For the additions, reclassifications and deletions to Y Pedwarau reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:











Myrddyn Phillips and Aled Williams (May 2017)



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