Mapping Mountains – Summit Relocations – Yr Uchafion and 500m Twmpau

Mynydd Ystradffernol (SN 937 009)

There has been a Summit Relocation to a hill that is listed in the Yr Uchafion and the 500m Twmpau, with the summit height, drop and status of the hill being confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips on the 25^th August 2018.

Mynydd Ystradffernol (SN 937 009)

The criteria for the two listings that this summit relocation applies to are:

Yr Uchafion – Welsh hills at or above 500m in height that have 15m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams, with the Introduction to this list appearing on Mapping Mountains on the 4^th November 2015.

500m Twmpau – Welsh hills at or above 500m and below 600m in height that have 30m minimum drop, with an accompanying sub category entitled the 500m Sub-Twmpau consisting of all Welsh hills at or above 500m and below 600m in height that have 20m or more and below 30m of drop.  With the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.  The list is authored by Myrddyn Phillips.

The name of the hill is Mynydd Ystradffernol, and it is adjoined to the Cymoedd Gwent range of hills, which are situated in the central part of South Wales (Region C, Sub-Region C2), and is positioned with the A 4061 road to the west and has the village of Treherbert towards the south.

As the summit of the hill is a part of designated open access land it can in theory be approached from any direction.  However, the hill is covered in an extensive conifer plantation which over recent years now incorporates many wind turbines.  The building of the wind farm has created access tracks and these can be used to ease passage toward the summit. 

Prior to the survey with the Trimble GeoXH 6000 the summit of this hill was listed near to where the 518m summit spot height appears on the Ordnance Survey 1:25,000 Explorer map, this position is at SN 93682 00905.

Two surveys were taken with the Trimble GeoXH 6000 with the following results:

1^st survey:  517.808m at SN 93790 00902

2^nd survey:  517.612m at SN 93676 00907

Gathering data at the summit of Mynydd Ystradffernol

The second data set taken for the summit position of Mynydd Ystradffernol

The second survey was taken to the highest ground close to where the 518m spot height appears on the Ordnance Survey 1:25,000 Explorer map.  However, the result produced by the Trimble for the first survey is higher and its position comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist, or when the summit of the hill is in a different field compared to where previously given, or when the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct.  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 relocations.

Extract from the Ordnance Survey 1:25,000 Explorer map showing the new summit position in relation to the old listed summit position at the 518m spot height

The summit height produced by the Trimble GeoXH 6000 survey is 517.8m and is positioned at SN 93790 00902.  This position is not given a spot height on Ordnance Survey maps and is approximately 100 metres east from where the previously listed summit position is situated.

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Cymoedd Gwent

Name:  Mynydd Ystradffernol

OS 1:50,000 map:  170

Summit Height:  517.8m (converted to OSGM15)

Summit Grid Reference (new position):  SN 93790 00902

  

Bwlch Height:  484.9m (converted to OSGM15)

Bwlch Grid Reference:  SN 92961 02194

Drop:  32.9m (converted to OSGM15)

For details on the survey that confirmed the summit relocation of this hill

Myrddyn Phillips and Aled Williams (January 2019)