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

 

Cwmcroyddir (SN 736 409) – 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. 

LIDAR image of Cwmcroyddir (SN 736 409)

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 Mountainspublication 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 Cwmcroyddir and this was derived from the Tithe map, and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its south and east, the A482 road farther to its south-west and the A483 road farther to its south-east, and has the town of Llanymddyfri (Llandovery) towards the south-south-east. 

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 31m of drop, based on the 348m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 317m bwlch height, based on interpolation of 10m contouring between 310m – 320m. 

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. 

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 316m bwlch spot height and when coupled with the 348m summit spot height, these values gave this hill 32m of drop. 

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 confirmation of the reclassification of this hill from Sub-Trichant status is due to LIDAR analysis, resulting in a 348.6m summit height and a 316.4m bwlch height, with these values giving this hill 32.2m of drop, which is sufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Mynydd Mallaen 

Name:  Cwmcroyddir 

OS 1:50,000 map:  146, 147, 160

Summit Height:  348.6m (LIDAR)                                                           

Summit Grid Reference:  SN 73605 40961 (LIDAR) 

Bwlch Height:  316.4m (LIDAR) 

Bwlch Grid Reference:  SN 73461 41222 (LIDAR) 

Drop:  32.2m (LIDAR) 

 

Myrddyn Phillips (March 2022)