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

Cae Mawr (SN 832 405) – 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 Cae Mawr (SN 832 405)

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 now listed by is Cae Mawr and this was derived from the Tithe map, and it is adjoined to the Mynydd Epynt group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north-west, the A483 road farther to its north-west and the A40 road to its south, and has the town of Llanymddyfri (Llandovery) 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 29m of drop, based on the 313m summit spot height and the 284m bwlch spot height that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

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 and the details for this hill were subsequently re-assessed against this mapping.  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.  This mapping had bwlch contouring between 280m – 285m, with interpolation placing the height of the bwlch as an estimated c 283m, with this position favoured over that of the 284m spot height, resulting in its drop value being amended to an estimated c 30m and its status reclassified to a Trichant. 

Bwlch contouring extract from the OS Maps website 

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 312.5m summit height and a 284.5m bwlch height, with these values giving this hill 28.0m of drop, which is insufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Mynydd Epynt 

Name:  Cae Mawr 

OS 1:50,000 map:  147, 160

Summit Height:  312.5m (LIDAR)                                                           

Summit Grid Reference:  SN 83261 40541 (LIDAR) 

Bwlch Height:  284.5m (LIDAR) 

Bwlch Grid Reference:  SN 84050 41511 & SN 84048 41515 (LIDAR) 

Drop:  28.0m (LIDAR) 

 

Myrddyn Phillips (January 2024)