Mapping Mountains – Significant Height Revisions – 200m Twmpau

 

Stingwern Wood (SJ 145 000)

There has been a Significant Height Revision to a hill that is listed in the 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data and a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

Stingwern Wood (SJ 145 000)

The criteria for the list this height revision affects are: 

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 200m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Stingwern Wood, and it is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is encircled by minor roads with the B4390 road further to its north, the B4389 road further to its west and the A483 road further to its south-east, and has the village of Aberriw (Berriew) towards the east. 

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website the qualifying hill was included in the main P30 list with a summit height of 251m positioned at SJ 154 997, which was taken from the spot height that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

After the accompanying sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 60m of drop, based on an estimated c 258m summit height and an estimated c 198m bwlch height, with both values based on interpolation of 10m contouring that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, with the summit also relocated to SJ 145 000. 

The summit of this hill has now been surveyed with the Trimble GeoXH 6000, resulting in 260.0m at SJ 14514 00063 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 summit 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 Stingwern Wood

Therefore, this hill’s new listed summit height is 260.0m and this was derived from a Trimble GeoXH 6000 survey, this is positioned at SJ 14514 00063 and is 2.0m higher than its previously listed height of c 258m and 9.0m higher than the origin qualifying listed summit of 251m, with the former based on interpolation of contours and the latter taken from the spot height on the Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  Carnedd Wen

Name:  Stingwern Wood

OS 1:50,000 map:  136

Summit Height (New Height):  260.0m (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference:  SJ 14514 00063 (Trimble GeoXH 6000) 

Bwlch Height:  c 198m (interpolation) 

Bwlch Grid Reference:  SJ 14414 00402 (interpolation) 

Drop:  c 62m (Trimble GeoXH 6000 summit and interpolated bwlch) 

 

Myrddyn Phillips (March 2021)