Mapping Mountains – Significant Name Changes – The Welsh P15s

 

Coed Gelli Lydan (SN 741 993) 

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 LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Coed Gelli Lydan (SN 741 993)

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 Banc Llechwedd Mawr group of hills, which are situated in the north-western part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its west, the A487 road to its north-west, and has the town of Machynlleth towards the north north-east.

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the main P15 list under the point (Pt. 172m) notation, with an estimated c 15m of drop, based on the 172m summit 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 an estimated c 157m bwlch height, based on interpolation of 10m contouring between 150m – 160m. 

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website, there have been a number of 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 were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites, and it is the series of Ordnance Survey Six-Inch maps that form the basis of the change in the listed name of this hill.

The Ordnance Survey series of Six-Inch maps formed the base map Ordnance Survey used for many decades leading to the production of the 1:10,000 Series of maps, both have now been superseded by the digitised Master Map.  The series of Six-Inch maps are excellent for name placement and especially so compared to the contemporary Ordnance Survey 1:25,000 Explorer map, and it is the series of Six-Inch maps that position the name of Coed Gelli Lydan to land where the summit of this hill is situated.

Extract from the Ordnance Survey series of Six-Inch maps

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

 

The full details for the hill are: 

Group:  Banc Llechwedd Mawr 

Name:  Coed Gelli Lydan 

Previously Listed Name:  Pt. 172m 

OS 1:50,000 map:  135

Summit Height:  171.8m (LIDAR)                                                           

Summit Grid Reference:  SN 74154 99355 (LIDAR)                                                  

Bwlch Height:  155.3m (LIDAR) 

Bwlch Grid Reference:  SN 74338 99421 (LIDAR) 

Drop:  16.5m (LIDAR) 

 

Myrddyn Phillips (June 2025)