Monday, 12 June 2017

Mapping Mountains – Hill Reclassifications – Y Pedwarau


Bryn yr Ysbyty (SN 985 995) – 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 hill being added to the 400m Sub-Pedwar categoryThe 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 originally catalogued with c 20m of drop which would have qualified it for 400m Sub-Pedwar status, this was re-evaluated and in doing so contours were misinterpolated, resulting in the hill being catalogued with c 14m of drop and therefore it was not considered for inclusion in the 400m Sub-Pedwar category.

The hill is situated in the Carnedd Wen range with its Cardinal Hill being Garreg Hir (SN 998 979) and is placed in the Region of North Wales (Region A, Sub-Region A4), and is positioned with the small community of Carno to the south-west and Clatter to the south south-east.

The hill is a part of designated open access land and although it is immersed in conifer plantation, a track enters the forest from east of the summit and gives access to a forest ride which ploughs its way through the conifers and comes relatively close to the high point, and dependent upon tree proximity any onward progress from here may prove problematic.

The name of the hill is Bryn yr Ysbyty 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:


Bryn yr Ysbyty

Summit Height:  435.2m

Summit Grid Reference:  SN 98523 99527

Bwlch Height:  413.3m

Bwlch Grid Reference:  SN 99024 99915

Drop:  21.9m


Therefore, the 435.2m LIDAR data produced for the summit position at SN 98523 99527 and the 413.3m LIDAR data produced for the bwlch position at SN 99024 99915 gives this hill 21.9m of drop which is sufficient for its inclusion as a 400m Sub-Pedwar.


The full details for the hill are:

Cardinal Hill:  Garreg Hir

Summit Height:  435.2m (LIDAR data)

Name:  Bryn yr Ysbyty

OS 1:50,000 map:  136

Summit Grid Reference:  SN 98523 99527

Drop:  21.9m (LIDAR data)


The total for Y Pedwarau remains at 442 hills with nine additions, and fourteen 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 219 with 24 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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