Mapping Mountains – Summit Relocations – 100m Twmpau

Bryn y Beudy (SH 507 404) 

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau, 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 Bryn y Beudy (SH 507 404)

The criteria for the list that this summit relocation applies to are:

100m Twmpau - Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Bryn y Beudy and this was derived from the Tithe map, and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with minor roads to its north and south, the B4411 road to its south-west and the A487 road to its north-east, and has the town of Cricieth towards the south.

When the original 100m 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-assessed and it was listed with 22m of drop, based on the 156m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and which is positioned at SH 50788 40454 and the 134m bwlch spot height 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

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 155.4m positioned at SH 50797 40464 and SH 50801 40464.  However, this is to the top 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 Bryn y Beudy (SH 507 404)

The height produced by LIDAR analysis to the natural summit of this hill is 155.2m and is positioned at SH 50785 40428 and SH 50786 40429, and this 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 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 height produced by LIDAR analysis to the natural summit of this hill is 155.2m and is positioned at SH 50785 40428 and SH 50786 40429, this position is relatively close to where the spot height appears on the contemporary Ordnance Survey 1:25,000 Explorer map, and is approximately 36 metres south-westward from the high point of the raised field boundary. 

 

The full details for the hill are: 

Group:  Moel Hebog 

Name:  Bryn y Beudy 

OS 1:50,000 map:  124

Summit Height:  155.2m (LIDAR) 

Summit Grid Reference (New Position):  SH 50785 40428 & SH 50786 40429 (LIDAR) 

Bwlch Height:  132.7m (LIDAR) 

Bwlch Grid Reference:  SH 51229 40222 (LIDAR) 

Drop:  22.5m (LIDAR) 

 

Myrddyn Phillips (May 2024)