Mapping Mountains – Summit Relocations – 30-99m Twmpau, Y Trechol – The Dominant Hills of Wales and Y Pellennig – The Remotest Hills of Wales

Ynys Bery (SM 701 219)

There has been confirmation of the higher summit of a twin map topped hill that is being detailed under the Summit Relocations heading, and the hill is listed in the 30-99m Twmpau, Y Trechol – The Dominant Hills of Wales and Y Pellennig – The Remotest Hills of Wales, with the summit height and its location confirmed by LIDAR analysis conducted by Aled Williams.

LIDAR image of Ynys Bery.  1m contour (black), 10m contour (red) and sea level (yellow)

The criteria for the three listings that this summit relocation 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.

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, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

Y Pellennig – The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has a minimum 15m of drop, the list is a joint compilation between Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet or print-booklet version on Mapping Mountains Publications with the up-to-date master list available on the Mapping Mountains site in Google Doc format.

The name of the hill is Ynys Bery and as its name implies it is an island, and it is adjoined to the Carn Llidi group of hills which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and is positioned to the south of the larger Ynys Dewi.

This hill was originally listed in the Welsh 30-99m P30 hills published on Geoff Crowder’s v-g.me website, with a 71m summit height and an accompanying note stating; Two tops of same height.  The 71m summit height appears as a spot height given to two separate tops on the Ordnance Survey 1:25,000 Explorer map with these positioned at SM 70058 21863 and SM 70183 21965.

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

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

The details for this hill were reassessed when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; this map is entitled the Interactive Coverage Map and the two twin map heighted 71m summits were again shown.

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 analysis confirms that the north-easterly of these two summits is the higher and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist, or when the summit of the hill is in a different field compared to where previously given, or when the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these relocations.

Therefore, the summit height produced by LIDAR analysis is 72.0m and is positioned at SM 70182 21959, this position is given a 71m spot height on the Ordnance Survey 1: 25,000 Explorer map and is approximately 150 metres north-east from where the other twin map heighted summit is positioned which LIDAR analysis gives as 71.9m at SM 70056 21859.

The full details for the hill are:

Group:  Carn Llidi

Name:  Ynys Bery

OS 1:50,000 map:  157

Summit Height:  72.0m (LIDAR)

Summit Grid Reference (new position):  SM 70182 21959 (LIDAR)

Bwlch Height:  N/A, sea level

Bwlch Grid Reference:  N/A, sea level

 

Drop:  72.0m (LIDAR)

Dominance:  100.00% (LIDAR)

Remoteness:  3.925 km

Myrddyn Phillips and Aled Williams (July 2019)

© Crown: CHERISH PROJECT 2019. Produced with EU funds through the Ireland Wales Co-operation Programme 2014-2020. All material made freely available through the Open Government Licence.