Mapping Mountains – Significant Height Revisions – Y Pedwarau

Mynydd Poeth (SH 953 513)

There has been a Significant Height Revision to a hill that is listed in the Y Pedwarau and which was initiated by a survey with the Trimble GeoXH 6000, with these details being retrospective as the survey that resulted in this height revision was conducted on 24^th December 2014.  The hill appeared in the listing of Y Pedwarau as a 400m Sub-Pedwar with c 29m of drop and was reclassified to a Pedwar due to the survey with the Trimble GeoXH 6000. 

The criteria for Pedwar status is all Welsh hills at or above 400m and below 500m in height that have 30m minimum drop.  Whilst the criteria for 400m Sub-Pedwar status is all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.

The name of the hill is Mynydd Poeth and it is situated in the Mynydd Hiraethog range of hills which are positioned in the north of Wales, and the survey was conducted on Christmas Eve in the company of Mark Trengove who had suggested the walk.

Mynydd Poeth can be easily accessed from the B4501 which skirts its eastern fringe, and it is situated to the north of the small community of Cerrigydrudion and to the south of the Alwen Reservoir.

The hill's summit height has been increased from its current Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map height, as prior to the survey with the Trimble GeoXH 6000 the hill was listed with a summit height of 417m based on the spot height that appears on both of these maps.  However, higher ground exists to the north of where this spot height is positioned.

Therefore this hill’s new summit height is 419.3m (converted to OSGM15) which is 2.3m higher than its previously listed height which came from the 417m spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

This hill is one of the rare examples that can claim a Hill Reclassification, Summit Relocation and a Significant Height Revision all from the one survey.

The full details for the hill are:

Cardinal Hill:  Mwdwl Eithin

Summit Height (New Height):  419.3m (converted to OSGM15)

Name:  Mynydd Poeth

OS 1:50,000 map:  116

Summit Grid Reference:  SH 95375 51301

  

Drop:  31.7m (converted to OSGM15)

Gathering data from the summit of Mynydd Poeth which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill

Myrddyn Phillips and Aled Williams (August 2015)