Mapping Mountains – Significant Height Revisions – Y Trichant

Mynydd yr Heol (SO 107 601)

There has been a Significant Height Revision initiated by a survey with the Trimble GeoXH 6000 to a hill that is listed in the Y Trichant, with the survey that resulted in this height revision conducted on the 3^rd October 2017.

The criteria for the listing this height revision affects are:

Y Trichant – Welsh hills at and above 300m and below 400m in height that have 30m minimum drop.  The list is authored by Myrddyn Phillips and the Introduction to the list and its re-naming was published on Mapping Mountains on the 13^th May 2017.

The name of the hill is Mynydd yr Heol and it is situated in the Fforest Glud range of hills which are in the eastern part of Mid and West Wales (Region B, Sub-Region B1), and the hill is positioned between the town of Llandrindod (Llandrindod Wells) to its west and the small community of Hundred House to its south.

The grazed summit of Mynydd yr Heol (SO 107 601)

As the summit of the hill is not on designated open access land permission to visit should be sought, for those wishing to do so the nearest public footpath is south of the summit and it passes over the bwlch of the hill in a west – east direction.  However, the easiest and most convenient ascent is from the east following a green track up the hill from the convenience of a minor lane.

Prior to the survey with the Trimble GeoXH 6000 the height of the hill was listed as 382m, with this taken from the summit spot height on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

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

The 386.8m (converted to OSGM15) summit height produced by the Trimble GeoXH 6000 is a dramatic increase from the previously listed summit height of 382m, and therefore it comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revision applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000, or a previous estimated summit height based on contour interpolation.  Also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  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.

The summit of this hill is easily identified and consists of closely cropped grass at the top of a field used for grazing.  Just below the summit to the south-west is a small, but steep section of exposed rock, similar to an old quarry, otherwise the summit area is not remarkable, except of course for its dramatic increase in known height.

Therefore, this hill’s new summit height is 386.8m (converted to OSGM15) which is 4.8m higher than its previously listed height of 382m which is shown on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

The full details for the hill are:

Cardinal Hill:  Gilwern Hill

Summit Height (New Height):  386.8m (converted to OSGM15)

Name:  Mynydd yr Heol

OS 1:50,000 map:  148

Summit Grid Reference:  SO 10793 60177  

       

Drop:  31.2m (converted to OSGM15)

Gathering data with the Trimble GeoXH 6000 from the summit of Mynydd yr Heol 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 (December 2017)