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

Allt yr Hafod (SN 668 442) 

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 detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Allt yr Hafod (SN 668 442)

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 name the hill is listed by is Allt yr Hafod, and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north, west and south-east and the A482 road to its south-west, and has the town of Llanbedr Pont Steffan (Lampeter) 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 with a summit height of 311m, based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map and which is positioned at SN 66875 44216. 

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 analysis gives the highest ground on this hill as 310.3m positioned at SN 66863 44189.  However, this is a part of a raised field boundary and protocols dictate that as this is deemed a relatively recent man-made construct such ground is discounted from the height of a hill. 

LIDAR summit image of Allt yr Hafod (SN 668 442)

LIDAR close up summit image of Allt yr Hafod (SN 668 442)

The height produced by LIDAR analysis to the natural summit of this hill is 310.2m positioned at SN 66859 44201, and this position in relation to the raised field boundary 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 310.2m and this is positioned at SN 66859 44201, this position is close to where the 311m spot height appears on the contemporary Ordnance Survey 1:25,000 Explorer map, and is approximately 12 metres northward from where the high point of the raised field boundary is positioned. 

 

The full details for the hill are:

Group:  Esgair Wen 

Name:  Allt yr Hafod 

OS 1:50,000 map:  146

Summit Height:  310.2m (LIDAR)                                                           

Summit Grid Reference (New Position):  SN 66859 44201 (LIDAR) 

Bwlch Height:  c 288m (interpolation) 

Bwlch Grid Reference:  SN 67104 44293 (interpolation) 

Drop:  c 22m (LIDAR summit and interpolated bwlch) 

 

Myrddyn Phillips (April 2023)