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

 

Hafod Las (SN 738 506) – 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 detail on contemporary maps produced from Ordnance Survey data. 

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. 

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

The name the hill is listed by is Hafod Las and it is adjoined to the Elenydd group of hills, which are situated in the central part of the Mid and West Wales Region (Region B, Sub-Region B2), and it is positioned with minor roads to its north, west, south and east, and has the village of Llanddewibrefi towards the north-west. 

When the original 300m height band of Welsh P30 hills was 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 385m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and the 1:25,000 Explorer map and an estimated c 354m bwlch height based on interpolation of 10m contouring between 350m – 360m that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

Since the publication of the P30 lists of Geoff Crowder’s v-g.me website there have been a number of Ordnance Survey 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 are current and digitally updated such as the old Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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 maps and for this hill it had a 354m bwlch spot height positioned at SN 73649 50811, and when coupled with the 385m summit spot height gave this hill 31m of drop. 

The details for this hill were subsequently re-assessed against 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.  This mapping had bwlch contouring between 355m – 360m with the position of the 354m bwlch spot height shown on the Ordnance Survey Vector Map Local below the 355m contour line.  This re-assessment resulted in the bwlch height being estimated as c 356m. 

Extract from the OS Maps website

Therefore, the reclassification of this hill to Sub-Trichant status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 385m summit height and an estimated c 356m bwlch height, with these values giving this hill an estimated c 29m of drop, which is insufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Elenydd 

Name:  Hafod Las 

OS 1:50,000 map:  146, 147

Summit Height:  385m (spot height)                                                           

Summit Grid Reference:  SN 73827 50659 (hand-held GPS via DoBIH) 

Bwlch Height:  c 356m (interpolation) 

Bwlch Grid Reference:  SN 73622 50811 (interpolation) 

Drop:  c 29m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (August 2021)