Mapping Mountains – Significant Height Revisions – Y Pedwarau – The 400m Hills of Wales

 

Bryn Berw (SN 714 505)

There has been a Significant Height Revision to a hill that is listed in the Y Pedwarau – The 400m 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 Bryn Berw (SN 714 505)

The criteria for the list that this height revision applies to are:

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being included in the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Bryn Berw, 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 a minor road to its north-east and west, and has the village of Llanddewibrefi towards the north-west.

When the original 400m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was included in the accompanying Hills to be surveyed sub list with a non-interpolated 430m summit height. 

Extract from the Ordnance Survey 1:25,000 Explorer map

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 28m of drop, based on the 433m summit spot height and the 405m 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.  And these are the details the hill was listed by when the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013.

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 Bryn Berw (SN 714 505)

LIDAR analysis gives the highest ground on this hill as 430.7m positioned at SN 71433 50501, 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, Harvey or other interactive 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 with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 430.7m and this was derived from LIDAR analysis, this is 2.3m lower than the previously listed summit height, which was based on the 433m spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Esgair Wen 

Name:  Bryn Berw 

OS 1:50,000 map:  146, 147

Summit Height (New Height):  430.7m (LIDAR) 

Summit Grid Reference:  SN 71433 50501 (LIDAR) 

Bwlch Height:  403.3m (LIDAR) 

Bwlch Grid Reference:  SN 71373 50607 (LIDAR) 

Drop:  27.4m (LIDAR)

 

Myrddyn Phillips and Aled Williams (March 2026)