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

 

Ffridd y Glyn (SH 816 080) – Sub-Trichant reclassified to Trichant

There has been confirmation of 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 and detail on contemporary maps produced from Ordnance Survey data. 

LIDAR image of Ffridd y Glyn (SH 816 080)

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 Ffridd y Glyn, and it is adjoined to the Aran Fawddwy group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with the A487 road to its west, the A489 road to its south and the A470 road to its east, and has the town of Machynlleth 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. 

After 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 32m of drop, based on the 306m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 274m bwlch height, based on interpolation of 10m contouring between 270m – 280m. 

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online.  Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website.  Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current such as the interactive mapping on the Magic Maps and WalkLakes websites. 

One of the resources recently available online is the mapping on the OS Maps website.  This is the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local.  Although the mapping on the OS Maps website no longer has contours at 5m intervals, such contours are represented on other mapping available online and for this hill this mapping has bwlch contouring between 275m – 280m, with interpolation placing the height of the bwlch as an estimated c 276m. 

Extract from online 5m contouring

Therefore, the confirmation of the reclassification of this hill from Sub-Trichant status is due to LIDAR analysis and detail on contemporary maps produced from Ordnance Survey data, resulting in a 306.5m summit height and an estimated c 276m bwlch height, with these values giving this hill an estimated c 30m of drop, which is sufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Aran Fawddwy 

Name:  Ffridd y Glyn 

OS 1:50,000 map:  124, 125

Summit Height:  306.5m (LIDAR)                                                           

Summit Grid Reference:  SH 81676 08091 (LIDAR) 

Bwlch Height:  c 276m (interpolation) 

Bwlch Grid Reference:  SH 81720 08732 (interpolation) 

Drop:  c 30m (LIDAR summit and interpolated bwlch) 

 

Myrddyn Phillips (February 2022)