Mapping Mountains – Summit Relocations – Y Trichant – The 300m Hills of Wales

Cefn Uchaf (SJ 012 461)

There has been a Summit Relocation to a hill that is listed in the Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cefn Uchaf (SJ 012 461)

The criteria for the list this summit relocation affects 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 Cefn Uchaf and this was derived from the Tithe map, and it is adjoined to the Mynydd Hiraethog group of hills which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned with the B5105 road to its north, the A5 road to its south and the A494 road to its east, and has the town of Corwen towards the east 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 not 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 this sub 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 2om of drop, based on the 337m summit spot height that appears at SJ 01390 46054 on the Ordnance Survey 1:25,000 Explorer map and the 317m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.

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

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.

LIDAR summit image of Cefn Uchaf

The summit height produced by LIDAR analysis is 340.0m positioned at SJ 01294 46112 and this revised summit position comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the hill’s high point is in a different field, or where a number of potential summit positions are within close proximity and the highest point is not where previously given, or when it is positioned to a different feature such as in a conifer plantation, or when the high point of the hill is placed within a different map contour, or when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the listed summit height of this hill is 340.0m and its new position is SJ 01294 46112, this position is not given a spot height on contemporary Ordnance Survey maps and is approximately 100 metres north-westward from where the previously listed summit is positioned.

The full details for the hill are:

Group:  Mynydd Hiraethog

Name:  Cefn Uchaf

OS 1:50,000 map:  116

Summit Height:  340.0m (LIDAR)

Summit Grid Reference (New Position):  SJ 01294 46112 (LIDAR)

Bwlch Height:  319.1m (LIDAR)

Bwlch Grid Reference:  SJ 00949 46115 (LIDAR)

Drop:  20.9m (LIDAR)

Myrddyn Phillips (August 2020)