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

Pen Diban (SH 112 205) - Pellennig reinstatement

There has been a reinstatement 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 summit survey conducted by Myrddyn Phillips and subsequent LIDAR bwlch analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips.

Pen Diban (SH 112 205)

The criteria for the list that this reinstatement 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 Pen Diban, and it is adjoined to the Yr Eifl group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned on Ynys Enlli; an island that has the nearest minor road to its north-east, and has the small community of Aberdaron towards the north-east.

When the original list that later became known as the Y Pellennig – The Remotest Hills of Wales was first compiled, this hill was included with an estimated c 15m of drop, based on the 20m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 5m bwlch height, based on interpolation of 10m contouring between 0 - 10m. 

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

Since the original compilation of this list 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 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.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had 5m contouring which enabled a better assessment for the interpolated bwlch height, and with contouring at the bwlch between 5m - 10m, a c 6m bwlch height was estimated, resulting in this hill being listed with an estimated c 14m of drop and its deletion from Pellennig status.

The hill was subsequently surveyed with the Trimble GeoXH 6000, resulting in 15m of drop, with a 20.0m summit height and a 5.0m bwlch height and its reinstatement to Pellennig status.

The Trimble GeoXH 6000 gathering data at the summit of Pen Diban (SH 112 205)

However, it was not until LIDAR became available that the bwlch 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 image of Pen Diban (SH 112 205)

Therefore, the reinstatement of this hill to Pellenig status is due to a Trimble GeoXH 6000 summit survey and LIDAR bwlch analysis, resulting in a 20.0m summit height and a 5.0m bwlch height, with these values giving this hill 15.0m of drop, which is sufficient for it to be classified as a Pellennig.

The full details for the hill are: 

Group:  Yr Eifl

Name:  Pen Diban

OS 1:50,000 map:  123

Summit Height:  20.0m (Trimble GeoXH 6000)

Summit Grid Reference:  SH 11235 20585 (Trimble GeoXH 6000)

Bwlch Height:  5.0m (LIDAR)

Bwlch Grid Reference:  SH 11274 20954 (LIDAR)   

Drop:  15.0m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

Remoteness:  5.710km

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

Myrddyn Phillips and Aled Williams (April 2015)