Mapping Mountains – Significant Name Changes – The Welsh P15s

 

Castell Tre Gof (SH 414 742) 

There has been a Significant Name Change 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 detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR bwlch image of Castell Tre Gof (summit at SH 414 742)

The criteria for the list that this name change 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 Phillips

The hill 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 A55 road to its north and a minor road to its immediate west, and has the town of Llangefni towards the east north-east. 

When the listing that became known as The Welsh P15s was being compiled, this hill was listed under the name of Castell Bryn Twr, which is a name that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, with an estimated c 16m of drop, based on the 73m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 57m bwlch height based on interpolation of 5m contouring between 55m – 60m. 

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

Since the initial compilation of this list there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the mapping on the Magic Maps and WalkLakes websites. 

One of the mapping resources now available online is the Ordnance Survey series of Six-Inch maps via the National Library of Scotland website.  This mapping preceded the 1:10,000 base maps and has proven an excellent resource for name placement and is much better for this compared to the publicly available Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.  And it is the Six-Inch map that places the name of Castell Tre Gof adjacent to the summit of this hill. 

Extract from the Ordnance Survey series of Six-Inch maps

Therefore, the name this hill is now listed by in The Welsh P15s is Castell Tre Gof and this was derived from the Ordnance Survey series of Six-Inch maps. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Castell Tre Gof

Previously Listed Name:  Castell Bryn Twr 

OS 1:50,000 map:  114, 115

Summit Height:  73m (spot height) 

Summit Grid Reference:  SH 41445 74256 (spot height) 

Bwlch Height:  56.2m (LIDAR) 

Bwlch Grid Reference:  SH 41795 75476 (LIDAR) 

Drop:  17m (spot height summit and LIDAR bwlch) 

 

Myrddyn Phillips (October 2021)