Mapping Mountains – Hill Reclassifications – Y Pellennig – The Remotest Hills of Wales

Ynys Arw (SH 266 945) - Pellennig addition 

There has been an addition to the listing of Y Pellennig – The Remotest 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 conducted by Myrddyn Phillips.

Ynys Arw (SH 266 945)

The criteria for the list that this addition applies to are:

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 15m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet and print-booklet version on Mapping Mountains Publications with the up-to-date master list available to download on the Mapping Mountains site in Google Doc format.

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Ynys Arw, and it is adjoined to the Mynydd Twr group of hills, which are situated in the north-western part of North Wales (Region C1, Sub-Region C1A), and it is positioned to the north-west of Ynys Môn on an archipelago that is known as Ynysoedd y Moelrhoniaid and The Skerries.

When this list was originally compiled this hill was not included as detail on the Ordnance Survey 1:25,000 giving an uppermost 10m contour ring was deemed insufficient for it to be considered as a Pellennig.

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

However, it was not until the Trimble GeoXH 6000 survey that an accurtae height could be given for the summit and when coupled with subsequent LIDAR analysis supplied by © Crown:  CHERISH PROJECT 2019 and conducted by Aled Williams that an accurate drop value could be given to this hill.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

The Trimble GeoXH 6000 gathering data at the summit of Ynys Arw

Therefore, the addition of this hill to Pellennig status is due to a Trimble GeoXH 6000 summit survey and LIDAR bwlch analysis, resulting in a 15.2m summit height and therefore also drop, which is sufficient for it to be classified as a Pellennig.  

The full details for the hill are: 

Group:  Mynydd Twr

Name:  Ynys Arw

OS 1:50,000 map:  114

Summit Height:  15.2m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 26647 94598 (Trimble GeoXH 6000)

Bwlch Height:  N/A

Bwlch Grid Reference:  N/A   

Drop:  15.2m (Trimble GeoXH 6000) 

Remoteness:  4.850km

For the additions and deletions to Y Pellennig – The Remotest Hills of Wales reported on Mapping Mountains please consult the following Change Register:

 

Y Pellennig – The Remotest Hills of Wales

© 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.

Myrddyn Phillips and Aled Williams (September 2015)