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

 

Mynydd Pen Lan (SH 783 090) – Trichant addition

There has been an addition based on confirmation of the higher summit position 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 detail on contemporary maps produced from Ordnance Survey data. 

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 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 Pen Lan, 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 minor roads to its north and west, the A487 road farther to its west and the A470 road to its east, and has the village of Aberllefenni towards the north-west. 

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 main P30 category, with the prioritised P30 status allocated to the 371m map heighted hill positioned at SH 781 091 with an accompanying note stating; 375m on 1984 1:50,000 map at GR784091. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated with the prioritised summit relocated and it was listed with an estimated c 39m of drop, based on the 375m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map and an estimated c 336m bwlch height, based on interpolation of 10m contouring between 330m – 340m that appear on the Ordnance Survey 1:25,000 Explorer map. 

Extract from the Ordnance Survey 1:50,000 Landranger 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 335m – 340m, with interpolation placing the height of the bwlch as an estimated c 338m. 

Therefore, the addition of this hill to Trichant status is due to detail on contemporary maps produced from Ordnance Survey data confirming the adjacent hill positioned at SH 781 091 as lower, resulting in a 375m summit height and an estimated c 338m bwlch height, with these values giving this hill an estimated c 37m of drop, which is sufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Aran Fawddwy 

Name:  Mynydd Pen Lan 

OS 1:50,000 map:  124

Summit Height:  375m (spot height)                                                           

Summit Grid Reference:  SH 78343 09027 (hand-held GPS via DoBIH) 

Bwlch Height:  c 338m (interpolation) 

Bwlch Grid Reference:  SH 78157 08694 (interpolation) 

Drop:  c 37m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (February 2022)