Mapping Mountains – Summit Relocations – The Welsh P15s

Bryn Cysegrfa (SN 643 521) 

There has been a Summit Relocation to a hill that is listed in the The Welsh P15s, 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 Cysegrfa (SN 643 521)

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

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Bryn Cysegrfa, 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 the B4343 road to its north-west and minor roads to its south-west and east, and has the town of Llanbedr Pont Steffan (Lampeter) towards the south-west.

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the main P15 list with an estimated c 20m of drop, based on the 337m summit spot height positioned at SN 64351 52092 that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 317m bwlch height, based on interpolation of 10m contouring between 310m – 320m. 

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 338.4m positioned at SN 64317 52119.  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 Bryn Cysegrfa (SN 643 521)

The height produced by LIDAR analysis to the natural summit of this hill is 338.3m positioned at SN 64313 52109, 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 to when the high point of the hill is positioned in a different field, to a different feature such as a conifer plantation, within a different map contour, a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit 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 338.3m and this is to the natural summit of the hill which is positioned at SN 64313 52109, 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 40 metres westward from where the 337m spot height appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and approximately 10 metres southward from where the high point of the raised field boundary is positioned. 

 

The full details for the hill are: 

Group:  Esgair Wen 

Name:  Bryn Cysegrfa 

OS 1:50,000 map:  146

Summit Height:  338.3m (LIDAR)                                                           

Summit Grid Reference (New Position):  SN 64313 52109 (LIDAR) 

Bwlch Height:  318.8m (LIDAR) 

Bwlch Grid Reference:  SN 64689 52334 (LIDAR) 

Drop:  19.5m (LIDAR) 

 

Myrddyn Phillips (April 2023)