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

 

Mynydd Jaram (SJ 183 219) – Trichant reclassified to Sub-Trichant

There has been a reclassification 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 derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Mynydd Jaram (SJ 183 219)

The criteria for the list that this reclassification 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 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Mynydd Jaram, and it is adjoined to the Foel Cedig group of hills, which are situated in the southern part of North Wales (Region A, Sub-Region A3), and it is positioned encircled by minor roads, with the B4396 road farther to its north, the B4580 road farther to its west and the B4393 road farther to its south, and has the town of Llanfyllin towards the south-west.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 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 31m of drop, based on the 336m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 305m bwlch height, based on interpolation of 10m contouring between 300m – 310m.  The bwlch height was subsequently re-assessed and listed as an estimated c 306m, resulting in the drop value being amended to an estimated c 30m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the reclassification of this hill to Sub-Trichant status is due to LIDAR analysis, resulting in a 336.6m summit height and a 307.7m bwlch height, with these values giving this hill 28.9m of drop, which is insufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Foel Cedig 

Name:  Mynydd Jaram 

OS 1:50,000 map:  125

Summit Height:  336.6m (LIDAR)                                                           

Summit Grid Reference:  SJ 18393 21961 (LIDAR) 

Bwlch Height:  307.7m (LIDAR) 

Bwlch Grid Reference:  SJ 18109 22085 (LIDAR) 

Drop:  28.9m (LIDAR) 

 

Myrddyn Phillips (July 2022)