Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales

Nyrs Fawr (SH 867 008) – Sub-Trichant addition

There has been confirmation of an addition to the list of Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips on the 29^th October 2019.

Nyrs Fawr (SH 867 008)

The criteria for the list that this addition applies to are:

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13th May 2017.

The name the hill is listed by is Nyrs Fawr and it is adjoined to the Pumlumon group of hills which are situated in the northern part of Mid and West Wales (Region B, Sub-Region B2), and it is positioned with the Afon Twymyn and the A470 road to its north and the B4518 road to its east, and has the village of Llanbrynmair towards the north-east. 

Gathering data at the summit of Nyrs Fawr

Gathering data at the bwlch of Nyrs Fawr

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for this sub category. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 23m of drop, based on the 365m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 342m based on interpolation of 10m contouring between 340m – 350m.

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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and included a 344m spot height on the area of this hill’s bwlch which decreased the listed drop to 21m.  This spot height is also shown on Ordnance Survey data that appears on the Magic Maps website.  However, it was not until the survey with the Trimble GeoXH 6000 that the status of this hill could be confirmed. 

Extract from the Magic Maps website

Therefore, the confirmation of the addition of this hill to Sub-Trichant status is due to a Trimble GeoXH 6000 survey, resulting in a 363.8m summit height and a 340.9m bwlch height, with these values giving this hill 22.9m of drop which is sufficient for it to be classified as a Sub-Trichant.

The full details for the hill are:

Group:  Pumlumon

Name:  Nyrs Fawr

OS 1:50,000 map:  135, 136

Summit Height:  363.8m (converted to OSGM15)

Summit Grid Reference:  SH 86771 00895

Bwlch Height:  340.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 86860 00561

Drop:  22.9m

Myrddyn Phillips (February 2020)