Mapping Mountains – Significant Height Revisions – Y Trichant and Y Trechol – The Dominant Hills of Wales

Upper Park (SJ 189 052)

There has been a Significant Height Revision to a hill that is listed in the Y Trichant and Y Trechol – The Dominant Hills of Wales, and which was initiated by a survey with the Trimble GeoXH 6000, with the survey that confirmed this height revision being conducted on the 7^th January 2018.

The criteria for the two listings that this height revision affects are:

Y Trichant - Welsh hills at and above 300m and below 400m in height that have 30m minimum drop. 

Y Trechol - The Dominant Hills of Wales - These are the Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those addition Welsh P30 hills whose prominence is 33% or more and below 50% of their absolute height.

The name of the hill is Upper Park and it is situated in the Carnedd Wen range of hills which are in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned between the A 458 road to its north and the A 483 road to its south-east, and has the town of Y Trallwng (Welshpool) to its north-east.

As the summit of the hill is not on designated open access land and is part of a private estate permission to visit should be sought, for those wishing to do so there are a number of options for an ascent, all of which use tracks through forested plantations.

Prior to the survey with the Trimble GeoXH 6000 the height of the hill was originally listed as 352m, with this taken from the spot height that appears on the Ordnance Survey 1:25,000 Explorer map, latterly the hill has been listed with an estimated c 353m summit height.

The 354.0m (converted to OSGM15) summit height produced by the Trimble GeoXH 6000 is not a dramatic increase from the 352m spot height, but 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 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, and also hill’s that do not possess a summit spot height and whose estimated summit height has a 2m or more discrepancy when compared to data produced either by the Trimble or by LIDAR.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these revisions.

Therefore, this hill’s new summit height is 354.0m (converted to OSGM15) which is 2.0m higher than the 352m spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

The full details for the hill are:

Group:  Carnedd Wen

Summit Height (New Height):  354.0m (converted to OSGM15)

Name:  Upper Park

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 18980 05270 

        

Drop:  177.0m (converted to OSGM15)

Dominance:  49.998%

The Trimble GeoXH 6000 gathering data at the summit of Upper Park (SJ 189 052) 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 (February 2018)