Myrddyn Phillips - Mapping Mountains: Foel Ganol

Showing posts with label Foel Ganol. Show all posts

Monday, 18 August 2025

Mapping Mountains – Significant Height Revisions – The 500-Metre Tops of England and Wales – Deweys

Foel Ganol (SH 687 715)

There has been a Significant Height Revision to a hill that is listed in the The 500-Metre Tops of England and Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams.

LIDAR image of Foel Ganol (SH 687 715)

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

The 500-Metre Tops of England and Wales are affectionately known after their hill list compiler; Michael Dewey. This list mixes metric and imperial height in its criteria to bookend up to the 2000ft height band and takes in all hills in England, Isle of Man and Wales that are 500m and above and below 2000ft (609.6m) in height that have 30m minimum drop.

Mountain tables by Michael Dewey

Michael Dewey died on the 5^th November 2022. His wife; Gillian wished for this list to be carried on and made provision for it to be co-authored by Myrddyn Phillips. Michael will always be the compiler and originator, it’s just that he’s now got a co-author to safeguard and carry this list on.

The name the hill is listed by is Foel Ganol and it is adjoined to the Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales, and it is positioned with the A55 road to its north-west and a minor road to its west, and has the town of Llanfairfechan towards the north.

When the original list of Deweys appeared in the Mountain tables book published by Constable in 1995, this hill was listed with a summit height of 536m, based on the spot height 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 summit image of Foel Ganol (SH 687 715)

LIDAR analysis gives the summit of this hill as 533.1m positioned at SH 68797 71588, and when compared to its originally listed summit height of 536m 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 533.1m and this was derived from LIDAR analysis, this is 2.9m lower than the originally listed summit height of 536m, which was based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.

The full details for the hill are:

Group: Carnedd Llywelyn

Name: Foel Ganol

OS 1:50,000 map: 115

Summit Height (New Height): 533.1m (LIDAR)

Summit Grid Reference: SH 68797 71588 (LIDAR)

Bwlch Height: 495.0m (LIDAR)

Bwlch Grid Reference: SH 69012 71563 (LIDAR)

Drop: 38.2m (LIDAR)

Myrddyn Phillips (August 2025)

Tuesday, 24 September 2024

Mapping Mountains – Significant Height Revisions – 500m Twmpau and Welsh Highlands – Uchafion Cymru

Foel Ganol (SH 687 715)

There has been a Significant Height Revision to a hill that is listed in the 500m Twmpau and the Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams.

LIDAR image of Foel Ganol (SH 687 715)

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

500m Twmpau – Welsh hills at or above 500m and below 600m in height that have 30m minimum drop, with an accompanying sub category entitled the 500m Sub-Twmpau consisting of all Welsh hills at or above 500m and below 600m in height that have 20m or more and below 30m of drop. With the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. The list is authored by Myrddyn Phillips and is published on Mapping Mountains in Google Doc format.

500m Twmpau by Myrddyn Phillips

Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop. This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The name the hill is listed by is Foel Ganol and it is adjoined to the Carnedd Llywelyn 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 A55 road to its north-west and a minor road to its west, and has the town of Llanfairfechan towards the north.

When the list of Welsh 500m P15s that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was listed with 40m of drop, based on the 536m summit spot height and the 496m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map.