Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

 

Pen Tyrau (SH 837 382) – Welsh Highland Sub addition 

There has been an addition to the listing of 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. 

Pen Tyrau (SH 837 382).  Photo: Aled Williams

The criteria for the list that this addition 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 Aled Williams and Myrddyn Phillips

The name the hill is listed by is Pen Tyrau, and it is adjoined to the Arenig Fawr group of hills, which are situated in the central part of North Wales (Region A, Sub-Region A2), and it is positioned with a minor road and the A4212 road to its north, and has the town of Y Bala towards the east south-east. 

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

The status of this hill has a convoluted history as it was originally listed with less than the required 10m minimum drop to qualify for sub status, and then included when the initial P10 sub list was completed in June 2020 and listed with 10.4m of drop, based on a basic levelling survey conducted by Myrddyn Phillips on the 14.09.98, and listed with a 697m summit height a 687m bwlch height, with an accompanying note stating that analysis of numerical data on various scales of Ordnance Survey maps give this hill an estimated c 9m of drop.  Therefore, it was included as a Welsh Highland Sub when the drop value of the subs was agreed upon and revised in July 2020. 

The Trimble GeoXH 6000 gathering data at the summit of Pen Tyrau.  Photo: Aled Williams

The hill was subsequently analysed via LIDAR by Aled Williams, resulting in a 697.8m summit height and a 688.1m bwlch height, with these values giving this hill 9.7m of drop, which is insufficient for it to be classified as a Welsh Highland Sub.  However, with the drop value relatively close to the qualifying criterion of 10m this hill was prioritised for a survey with the Trimble GeoXH 6000. 

The Trimble GeoXH 6000 gathering data at the bwlch of Pen Tyrau.  Photo: Aled Williams

Therefore, the addition of this hill to Welsh Highland Sub status is due to a Trimble GeoXH 6000 survey, resulting in a 697.4m summit height and a 687.4m bwlch height, with these values giving this hill 10.0m of drop, which is sufficient for it to be reinstated as a Welsh Highland Sub. 

 

The full details for the hill are: 

Group:  Arenig Fawr

Name:  Pen Tyrau           

OS 1:50,000 map:  124, 125

Summit Height:  697.4m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 83737 38250 (Trimble GeoXH 6000)

Bwlch Height:  687.4m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 83601 38142 (Trimble GeoXH 6000)   

Drop:  10.0m (Trimble GeoXH 6000) 

 

For the additions, deletions and reclassifications to the Welsh Highlands – Uchafion Cymru reported on Mapping Mountains please consult the following Change Registers:

 

Welsh Highland P15s

 

Welsh Highland Subs

 

Aled Williams and Myrddyn Phillips (November 2024)