Mapping Mountains – Significant Name Changes – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales

Ynys Fach (SN 668 951) 

There has been a Significant Name Change to a hill that is listed in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived by Joe Nuttall who produced a summit analysis programme using LIDAR, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips. 

LIDAR image of Ynys Fach (SN 668 951)

The criteria for the two listings that this name change applies to are: 

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 30-99m Twmpau by Myrddyn Phillips

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and which is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The hill is adjoined to the Pumlumon group of hills which are situated in the north-western part of Mid and West Wales (Region B, Sub-Region B2), and it has the A487 road to its south-east and the town of Machynlleth towards the north-east. 

The hill appeared in the original 30-99m Welsh P30 list on Geoff Crowder’s v-g.me website under the transposed name of Ynys Greigiog, which is a prominent name that appears adjacent to this hill on contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps.

Ynys Greigiog

30c

SN670948

135

23

 

During my early hill listing I paid little regard to name placement on the map, or the meaning of names and to what feature the name was appropriately applied to.  Therefore, I prioritised names for listing purposes that I now understand are either inappropriate or where another name is viewed as being more appropriate. 

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

Since publication of these P30 lists on Geoff Crowder’s v-g.me website 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 Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, and the interactive mapping on the Magic Maps and WalkLakes websites, and it is the Ordnance Survey series of Six-Inch maps that give the name of Ynys Fach. 

Extract from the Ordnance Survey series of Six-Inch maps

Therefore, the name this hill is now listed by in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales is Ynys Fach and this was derived from the Ordnance Survey series of Six-Inch maps. 

 

The full details for the hill are: 

Group:  Pumlumon 

Name:  Ynys Fach

Previously Listed Name:  Ynys Greigiog 

OS 1:50,000 map:  135

Summit Height:  43.5m (LIDAR) 

Summit Grid Reference:  SN 66845 95141 (LIDAR) 

Bwlch Height:  2.1m (LIDAR) 

Bwlch Grid Reference:  SN 67483 95096 (LIDAR) 

Drop:  41.3m (LIDAR) 

Dominance:  95.10% (LIDAR)

 

Myrddyn Phillips (April 2021)