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

Pen Moel Hedog (SN 451 469) 

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 Pen Moel Hedog (SN 451 469)

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 Pen Moel Hedog, 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 B4459 road to its west, the A475 road to its south and a minor road to its east, and has the town of Llanybydder 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, 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 23m of drop, based on the 314m summit spot height positioned at SN 45142 46935 that appears on the contemporary Ordnance Survey 1:25,000 Explorer map, and an estimated c 291m bwlch height, based on interpolation of 5m contouring between 290m – 295m. 

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 313.5m positioned at SN 45168 46943.  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 Pen Moel Hedog (SN 451 469)

The height produced by LIDAR analysis to the natural summit of this hill is 312.8m positioned at SN 45159 46968, 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 312.8m and this is positioned at SN 45159 46968, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 35 metres north-eastward from where the 314m spot height appears on the Ordnance Survey 1:25,000 Explorer map and approximately 25 metres north north-westward from the high point of the raised field boundary. 

 

The full details for the hill are:

Group:  Mynydd Bach 

Name:  Pen Moel Hedog 

OS 1:50,000 map:  146

Summit Height:  312.8m (LIDAR)                                                           

Summit Grid Reference (New Position):  SN 45159 46968 (LIDAR) 

Bwlch Height:  289.8m (LIDAR) 

Bwlch Grid Reference:  SN 45622 48279 (LIDAR) 

Drop:  23.0m (LIDAR) 

 

Myrddyn Phillips (January 2024)