Friday, 12 May 2017

Mapping Mountains – Hill Reclassifications – Y Pedwarau


Fynach Fawr (SN 727 890) – Pedwar reclassified to 400m Sub-Pedwar

There has been a reclassification to the listing of Y Pedwarau with a Pedwar being reclassified to a 400m Sub-Pedwar 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 reclassification 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 listed with c 32m of drop based on the 464m summit spot height on Ordnance Survey 1:25,000 Explorer maps and an estimated bwlch height of c 432m based on bwlch contouring between 430m – 440m.

The hill is situated in the Pumlumon group of hills with its Cardinal Hill being Banc Llechwedd Mawr (SN 775 898) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B2), and is positioned with the small community of Tal-y-bont to its west and Ponterwyd to its south south-east.

As the whole upper part of the hill is immersed in conifer plantation visiting its summit may prove to be a battle, with easiest access possibly via the north-west where the Ordnance Survey enlarged mapping hosted on the Geograph website indicates that there is a forest ride following the course of an old fence line to approximately 150 metres north of the summit.

The name of the hill is Fynach Fawr and its reclassification from Pedwar to 400m Sub-Pedwar 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:


Fynach Fawr

Summit Height:  461.4m

Summit Grid Reference:  SN 72715 89052

Bwlch Height:  432.5m

Bwlch Grid Reference:  SN 72911 89412

Drop:  28.9m


Therefore, the 461.4m LIDAR data produced for the summit position at SN 72715 89052 and the 432.5m LIDAR data produced for the bwlch position at SN 72911 89412 gives this hill 28.9m of drop which is insufficient for its continued inclusion as a Pedwar.


The full details for the hill are:

Cardinal Hill:  Banc Llechwedd Mawr

Summit Height:  461.4m (LIDAR data)

Name:  Fynach Fawr

OS 1:50,000 map:  135

Summit Grid Reference:  SN 72715 89052

Drop:  28.9m (LIDAR data)


This reclassification now brings the total for Y Pedwarau to 444 hills with eight additions, and eleven 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 218 with 20 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)


No comments: