Tuesday, 6 June 2017

Mapping Mountains – Hill Reclassifications – Y Pedwarau


Bryn Crugog (SN 941 923) – 400m Sub-Pedwar reclassified to Pedwar

There has been a reclassification 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 hill being reclassified from a 400m Sub-Pedwar to a Pedwar.  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 20m of drop based on the 447m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated bwlch height of c 427m based on interpolation of bwlch contouring between 420m – 430m.  The reclassification of this hill is dependent upon the analysis of LIDAR data for it, and its adjacent north-westerly hill of Esgair Hir (SN 937 925), with the height of the highest hill swapping, with this affecting the position of the critical bwlch of both hills and their status.  The Hill Reclassifications post for Esgair Hir will appear separately.

The hill is situated in the Pumlumon range with its Cardinal Hill being Bryn Amlwg (SN 921 973) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B2), and is positioned with the small community of Llawr-y-glyn to the south-west.

As the summit is not a part of designated open access land permission to visit should be sought, however there is a public footpath that approaches from the east and heads just south of the high point of the hill.

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


Bryn Crugog

Summit Height:  446.7m

Summit Grid Reference:  SN 94130 92357

Bwlch Height:  394.0m

Bwlch Grid Reference:  SN 93183 93473

Drop:  52.7m


Therefore, the 446.7m LIDAR data produced for the summit position at SN 94130 92357 and the 394.0m LIDAR data produced for the bwlch position at SN 93183 93473 gives this hill 52.7m of drop which is sufficient for its reclassification to a Pedwar.


The full details for the hill are:

Cardinal Hill:  Bryn Amlwg

Summit Height:  446.7m (LIDAR data)

Name:  Bryn Crugog

OS 1:50,000 map:  136

Summit Grid Reference:  SN 94130 92357

Drop:  52.7m (LIDAR data)


This reclassification now brings the total for Y Pedwarau to 443 hills with nine additions, and thirteen 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 22 hills being added and 18 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 (June 2017)


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