Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales

Lan Ganol (SN 973 571) – Sub-Trichant addition

There has been confirmation of an addition to the list of 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 a Trimble GeoXH 6000 survey and LIDAR analysis conducted by Myrddyn Phillips. 

Lan Ganol (SN 973 571)

The criteria for the list that this addition 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 Lan Ganol, and it is adjoined to the Drygarn Fawr group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4358 road to its south-east, and has the village of Newbridge-on-Wye towards the east north-east.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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 24m of drop, based on the 377m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 353m 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.

However, it was not until the survey with the Trimble GeoXH 6000 coupled with LIDAR analysis 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 Lan Ganol (SN 973 571)

Therefore, the confirmation of the addition of this hill to Sub-Trichant status is due to a Trimble GeoXH 6000 survey and LIDAR analysis, resulting in a 375.3m summit height and a 351.8m bwlch height, with these values giving this hill 23.5m of drop, which is sufficient for it to be classified as a Sub-Trichant. 

 

The full details for the hill are: 

Group:  Drygarn Fawr 

Name:  Lan Ganol 

OS 1:50,000 map:  147

Summit Height:  375.3m (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference:  SN 97371 57189 (Trimble GeoXH 6000) 

Bwlch Height:  351.8m (LIDAR) 

Bwlch Grid Reference:  SN 97732 57107 (LIDAR) 

Drop:  23.5m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

Myrddyn Phillips (April 2023)