Friday, 25 November 2016

Mapping Mountains – Hill Reclassifications – Yr Uchafion

Carnedd y Ddelw (SH 708 705) - Uchaf deletion

There has been a deletion to the listing of Yr Uchafion instigated from analysis of LIDAR data by Aled Williams, and subsequently confirmed via a line survey for drop and a Leica GS15 survey for height conducted by John Barnard and Graham Jackson.  Yr Uchafion is the draft title for a list of the Welsh 500m P15s that takes in all hills in Wales at or above 500m that have a minimum of 15m of drop, the list is a joint compilation with Aled Williams.  Details relating to this list were published on the Mapping Mountains site in November 2015.

The hill is situated in the Carneddau group of hills in the northern part of the Parc Cenedlaethol Eryri (Snowdonia National Park) in the Region of North Wales and is situated directly northward of Drum (SH 708 695) with Carnedd Llywelyn being its Cardinal Hill, and it is positioned above the town of Llanfairfechan to its north north-west and the small community of Tal-y-bont to its east south-east.

The hill can be easily accessed from its north-east from the car park at the end of the narrow lane that makes its way to the top of Bwlch y Ddeufaen.  This car park is situated at SH 720 715 and enables an ascent of the hill from the convenience of a starting point of around 420m in height.  The hill can also be combined with its higher neighbours to the south or the lower peaks to its north-west.

The name of the hill is Carnedd y Ddelw and its deletion as an Uchaf is due to the analysis of LIDAR data by Aled.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales, and as mentioned in the first paragraph of this post; if Carnedd y Ddelw does not have the minimum of 15m of drop it would be deleted from the listing of Welsh hills at or over 500m in height that has a minimum of 15m of drop, and has the working title of Yr Uchafion.

Aled’s analysis of LIDAR data gives the hill a 685.6m summit height at SH 70810 70531, and a 672.0m bwlch height at SH 70873 70344, these values give this hill 13.6m of drop which is insufficient for qualification as an Uchaf.

The LIDAR data analysed by Aled has a prescribed margin of uncertainty of +/- 0.15m, whilst the Ordnance Survey 688m summit height and 673m bwlch height each have a prescribed margin of uncertainty of +/- 3m.

This now revises the total in Yr Uchafion which will be updated accordingly and the hill is now deleted as an Uchaf.

The full details for the hill are:

Cardinal Hill:  Carnedd Llywelyn

Summit Height:  686.0m (Leica GS15 data)

Name:  Carnedd y Ddelw

OS 1:50,000 map:  115

Summit Grid Reference:  SH 70814 70535 
Drop:  13.97m (Line Survey)

The reclassifications to Yr Uchafion / The Welsh 500m P15s reported on Mapping Mountains are ills of wales as follows:




Carnedd y Ddelw (LIDAR data) (SH 708 705) Uchaf deletion with 13.97m of drop.

Carnedd y Ddelw (SH 708 705) now deleted from the listing of Yr Uchafion

Myrddyn Phillips and Aled Williams (November 2016)

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