Mapping Mountains – Significant Height Revisions – Y Trichant – The 300m Hills of Wales

 

Pared y Cefn Hir (SH 665 152) 

There has been a Significant Height Revision 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. 

Pared y Cefn Hir (SH 665 152)

The criteria for the list that this height revision 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 Pared y Cefn Hir, and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with the A493 road to its north-west and minor roads to its south-west, south-east and east, and has the town of Abermaw (Barmouth) 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.  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 374m summit height based on interpolation of the uppermost 370m contour that appears on the Ordnance Survey 1:25,000 Explorer 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 image of Pared y Cefn Hir (SH 665 152)

LIDAR analysis gives the summit height of this hill as 379.0m 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 summit 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, the new listed summit height of this hill is 379.0m and this was derived from LIDAR analysis, this is 5.0m higher than the previously listed summit height of c 374m which was estimated from interpolation of the uppermost 370m contour that appears on the contemporary Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are: 

Group:  Cadair Idris 

Name:  Pared y Cefn Hir 

OS 1:50,000 map:  124

Summit Height (New Height):  379.0m (LIDAR)                                                           

Summit Grid Reference:  SH 66579 15214 (LIDAR) 

Bwlch Height:  358.4m (LIDAR) 

Bwlch Grid Reference:  SH 66538 15146 (LIDAR) 

Drop:  20.5m (LIDAR) 

 

Myrddyn Phillips (March 2022)