Mapping Mountains – Significant Height Revisions – The Welsh P15s

 

Parc y Ffynnon (SH 634 808) 

There has been a Significant Height Revision to a hill that is listed in 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 Parc y Ffynnon (SH 634 808)

The criteria for the list that this height revision 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 Phillps

The name the hill is listed by is Parc y Ffynnon and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north, south and east and a minor road to its immediate west, and has the village of Llangoed towards the south-west. 

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the P14 sub list with 14m of drop, based on the 59m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 44m 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 summit image of Parc y Ffynnon

The summit height produced by LIDAR analysis is 60.6m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 60.6m and this was derived from LIDAR analysis, this is 1.6m higher than the previous listed summit height of 59m that appears as a spot height on the Ordnance Survey 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Ynys Môn 

Name:  Parc y Ffynnon 

OS 1:50,000 map:  114, 115

Summit Height (New Height):  60.6m (LIDAR)                                                           

Summit Grid Reference:  SH 63430 80880 (LIDAR) 

Bwlch Height:  44.8m (LIDAR) 

Bwlch Grid Reference:  SH 63199 81029 (LIDAR) 

Drop:  15.8m (LIDAR) 

 

Myrddyn Phillips (June 2021)