Mapping Mountains – Significant Height Revisions – Y Pedwarau

Craig Celynin (SH 746 733)

There has been a Significant Height Revision to a hill that is listed in the Y Pedwarau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips which took place on the 22^nd May 2019.

Craig Celynin (SH 746 733)

The criteria for the list this height revision applies to are:

Y Pedwarau – Welsh hills at or above 400m and below 500m in height that have a minimum 30m of drop, whilst the criteria for 400m Sub-Pedwar status are 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, with the Introduction to the Mapping Mountains publication of this list appearing on the 30^th January 2017.

The name of the hill is Craig Celynin and it is adjoined to the Carneddau group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A55 road and the coast to its north, and has the town of Conwy towards the north-east.

When the original Welsh 400m P30 list was published on Geoff Crowder’s v-g.me website this hill was listed with a 407m summit height, based on the spot height positioned at SH 746 733 that appears on the Ordnance Survey 1:25,000 Explorer map.

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

The summit height produced by the Trimble GeoXH 6000 survey is 404.8m, this is not a dramatic height revision when compared to some revised heights, but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis.

The Trimble GeoXH 6000 gathering data at the summit of Craig Celynin

Therefore, this hill’s new listed summit height is 404.8m and this was produced by a Trimble GeoXH 6000 survey, this is 2.2m lower than its previously listed height of 407m that appears as a spot height on the Ordnance Survey 1:25,000 Explorer map.

The full details for the hill are:

Group:  Carneddau

Name:  Craig Celynin

OS 1:50,000 map:  115

Summit Height (New Height):  404.8m (converted to OSGM15)

Summit Grid Reference:  SH 74667 73373

   

Bwlch Height:  377.1m (converted to OSGM15)

Bwlch Grid Reference:  SH 74604 73263

Drop:  27.7m (converted to OSGM15)

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

Myrddyn Phillips and Aled Williams (August 2019)