Mapping Mountains – Hill Reclassifications – Y Pedwarau - The 400m Hills of Wales

Y Garn (SH 758 375) - 400m Sub-Pedwar reclassified to Pedwar

There has been a retrospective of a hill in listing of the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey and subsequent LIDAR analysis conducted by Myrddyn Phillips and Aled Williams.

Y Garn (SH 758 375)

The criteria for the list that this reclassification applies to are:

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being reclassified from the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Y Garn, and it is adjoined to the Arenig Fach group of hills, which are situated in the central part of North Wales (Region C1, Sub-Region C1A), and it is positioned with the B4391 road to its north-east and the A4212 road to its south, and has the village of Trawsfynydd towards the west south-west.

When the original 400m height band of Welsh P30 hills compiled by Myrddyn Phillips was published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list with a 474m summit height, based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

Extract from the Ordnance Survey 1:25,000 Explorer map

However, this hill along with its adjacent hill of Ffridd Tan Rallt (SH 75906 37969) have a convoluted listing history, and this up until the Trimble Ge0XH 6000 survey and subsequent LIDAR analysis is detailed below:

Geoff Crowder’s Backpacking website (v-g.me)    Year: 2002    Author:  Myrddyn Phillips    List:  The Welsh 400 Metre Peaks

Y Garn                      SH 759 375          474m 

    

Pen Llyn y Garn      SH 759 378      c 470

The name of Pen Llyn y Garn is an invented name and has no historical or local credence

RHB File Database      Year:  2002 (Nov)      Author:  Myrddyn Phillips (with additional data later added by the late E.D. ‘Clem’ Clements)      List:  400m Hills of England, Isle of Man and Wales

Y Garn (S Top)                                      SH 759 375      474m          c 38m drop

Y Garn: N Top (Pen Llyn y Garn)      SH 759 379     476sd            33m drop

RHB File Database (latterly Hill Bagging website)      Year:  2009      Author:  Mark Jackson      List:  Tumps

Y Garn      SH 759 379      476m      33m drop

Europeaklist      Year:    2013      Authors:  Myrddyn Phillips and Aled Williams      List:  Y Pedwarau

Pt. 479m      SH 758 379      479m      34m drop

Y Garn          SH 758 375      474m      29m drop 

However, it was not until the Trimble GeoXH 6000 survey and when LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

The Trimble GeoXH 6000 gathering data at the summit of Y Garn

Therefore, the reclassification of this hill from 400m Sub-Pedwar status is due to a Trimble GeoXH 6000 survey, with details from subsequent LIDAR analysis used for its bwlch, resulting in a 474.2m summit height and a 443.6m bwlch height, with these values giving this hill 30.7m of drop, which is sufficient for it to be classified as a Pedwar. 

The full details for the hill are:

Group:  Arenig Fach

Name:  Y Garn

OS 1:50,000 map:  124

Summit Height:  474.2m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 75874 37543 (Trimble GeoXH 6000)

Bwlch Height:  443.6m (LIDAR)

Bwlch Grid Reference:  SH 75812 37838 (LIDAR)   

Drop:  30.7m (Trimble GeoXH 6000 summit and LIDAR bwlch)

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau 

Myrddyn Phillips and Aled Williams (March 2014)