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

Coed Bryndansi (SH 855 740) – 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 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 13th May 2017.

The name the hill is listed by is Coed Bryndansi and it is adjoined to the Rhos group of hills which are situated in the northern part of North Wales (Region A, Sub-Region A2), and it is positioned with the B5381 road to its north, the B5113 road to its west and minor roads to its south and east, and has the village of Llansanffraid Glan Conwy towards the west 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 included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for the main P30 list. 

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 estimated with c 27m of drop, based on an estimated c 303m summit height and an estimated c 276m bwlch height with the latter based on interpolation of 10m contouring between 270m – 280m.

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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and also for this area it had contour intervals at 5m.  This re-assessment resulted in this hill being listed with c 30m of drop based on an estimated c 303m summit height and an estimated c 273m bwlch height with the latter based on interpolation of 5m contouring between 270m – 275m.

The details for this hill were also re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has contours at 5m intervals which are proving consistently more accurate compared to the 5m contours that sometimes appear on Ordnance Survey 1:25,000 Explorer maps and used to appear on the online Vector Map Local.  This latest re-assessment also resulted in an estimated bwlch height of c 273m resulting in a drop value of c 30m.

The estimated summit height was substantiated when the Ordnance Survey series of Six-Inch maps were examined, as this mapping shows a 995.1ft (303.1m) Surface height for this hill.

Extract from the Ordnance Survey series of Six-Inch maps

When the Ordnance Survey Vector Map Local that was hosted on the Geograph website and entitled the Interactive Coverage Map became unavailable it was replaced with another Ordnance Survey product that showed a number of spot heights not on other publicly available Ordnance Survey maps.  This latest mapping does not have contours, but for this hill it shows a 304m summit spot height positioned at SH 85567 74121, which corresponds with the approximate position of the aforementioned Surface height.

Extract from the Ordnance Survey non-contour Vector Map Local hosted on the Geograph wbsite

Another resource now available online is the WalkLakes website which hosts an interactive map originated from the Ordnance Survey Open Data programme.  This map has many spot heights not on other publicly available Ordnance Survey maps and for this hill it shows a 305m summit spot height positioned at SH 85531 74002.

Extract from the WalkLakes website

Therefore, the confirmation of the reclassification of this hill to Trichant status is due to detail derived from contemporary maps produced from Ordnance Survey data, resulting in a 305m summit height and an estimated bwlch height of c 273m, with these values giving this hill c 32m of drop, which is sufficient for it to be classified as a Trichant.

The full details for the hill are:

Group:  Rhos

Name:  Coed Bryndansi

OS 1:50,000 map:  116

Summit Height:  305m (spot height)

Summit Grid Reference:  SH 85531 74002 (spot height)

Bwlch Height:  c 273m (interpolation)

Bwlch Grid Reference:  SH 85239 74303 (interpolation)

Drop:  c 32m (spot height summit and interpolated bwlch)

Myrddyn Phillips (March 2020)