Mapping Mountains – Significant Height Revisions – Welsh Highlands – Uchafion Cymru

Tryfan (SH 664 594) 

There has been a Significant Height Revision to a hill that is listed in the Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey conducted by Aled Williams. 

Tryfan (SH 664 594) (Photo: Aled Williams)

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

Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

Welsh Highlands - Uchafion Cymru by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Tryfan and it is adjoined to the Glyder Fawr 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 A5 road to its north and the A4086 road to its south, and has the village of Capel Curig towards the east south-east.

When the P10 sub list was compiled this hill was listed with 12.6m of drop, based on a basic levelling survey conducted by Myrddyn Phillips on the 01.05.98, with the summit height listed as 899m and the bwlch height as 886m, with both heights based on interpolation of contouring that appear on contemporary Ordnance Survey maps. 

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

The summit of this hill has now been surveyed with the Trimble GeoXH 6000, resulting in a 900.0m summit height positioned at SH 66422 59485, and this height comes 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 set-up position at the summit of Tryfan (SH 664 594) (Photo: Aled Williams)

The Trimble GeoXH 6000 gathering data at the summit of Tryfan (SH 664 594) (Photo: Aled Williams) 

Therefore, the new listed summit height of this hill is 900.0m and this was derived from a Trimble GeoXH 6000 survey, this is positioned at SH 66422 59485 and is 1.0m higher than its previously listed height of 899m which was based on the drop value ascertained from a basic levelling survey compared to Ordnance Survey map contouring, and is 10.0m higher than the uppermost contour on the contemporary Ordnance Survey 1:25000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Glyder Fawr

Name:  Tryfan

OS 1:50,000 map:  115

Summit Height (New Height):  900.0m (converted to OSGM15)

Summit Grid Reference:  SH 66422 59485  

Bwlch Height:  887.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 66385 59441

Drop:  12.5m

 

Aled Williams and Myrddyn Phillips (March 2023)