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

 

Pt. 329.7m (SN 591 630) 

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 derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pt. 329.7m (SN 591 630)

The criteria for the list that this summit relocation 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 hill is being listed by the point (Pt. 329.7m) notation and it is adjoined to the Mynydd Bach group of hills, which are situated in the western part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4576 road to its north-west, B4577 road to its south and a minor road to its east, and has the village of Llangeitho towards the 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, as it was considered not to meet the criteria then used for this sub 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 20m of drop, based on an estimated c 327m summit height and an estimated c 307m bwlch height, with both heights based on interpolation of 5m contouring that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage 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 and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites.

One of the mapping resources now available online is on the Magic Maps website which hosts an interactive map originated from Ordnance Survey data.  Until recently this mapping had many spot heights not on other publicly available maps and for this hill it had a 327m spot height on the summit area of this hill and positioned at SN 59019 63010, resulting in its details being amended accordingly. 

Extract from the interactive mapping hosted on the Magic 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. 

LIDAR summit image of Pt. 329.7m (SN 591 630)

LIDAR analysis gives the highest ground on this hill as 329.7m positioned at SN 59108 63024, and this in relation to the previously listed 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 high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour, to a different point where a number of potential summit positions are within close proximity, 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 or covered reservoir that is considered 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 summit height produced by LIDAR analysis is 329.7m and this is positioned at SN 59108 63024, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and the 1:25,000 Explorer map, and is approximately 90 metres eastward from where the previously listed summit is positioned which was based on the 327m spot height that appeared on the interactive mapping hosted on the Magic Maps website, and importantly the summit is positioned to a different feature. 

 

The full details for the hill are:

Group:  Mynydd Bach 

Name:  Pt. 329.7m 

OS 1:50,000 map:  146

Summit Height:  329.7m (LIDAR)                                                           

Summit Grid Reference (New Position):  SN 59108 63024 (LIDAR) 

Bwlch Height:  306.9m (LIDAR) 

Bwlch Grid Reference:  SN 59361 63409 & SN 59359 63413 (LIDAR) 

Drop:  22.8m (LIDAR) 

 

Myrddyn Phillips (November 2023)