Sunday, 31 July 2016

Mapping Mountains – Significant Height Revisions – Y Trichant

Penmaen Mawr (SH 704 752)

This is the thirty first post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 14th July 2016 in good, clear conditions in the early evening, with the hill subsequently analysed with LIDAR data by Aled Williams and it is the latter result that is being detailed in this Significant Height Revisions post.

The thirty first major height revision initialised by a survey with the Trimble GeoXH 6000 was conducted in the hills of the northern Carneddau in the company of Aled Williams who had suggested the walk and researched what needed surveying.

The hill is positioned above and to the immediate south of the busy A 55 as it heads westward between the towns of Penmaenmawr and Llanfairfechan, which are situated to the hill’s east and west respectively.

The summit is a part of the hill named Penmaen Mawr and the extended hill has been quarried with its old 1,550ft (472m) map heighted summit now a distant memory as the whole inner section of the summit has been blown apart leaving two remaining tops with this post concentrating on the lower easterly summit.

The lower easterly summit is impressive as it forms a sheer rock face from its south and has steep slopes descending northward to the A 55 below. 

The summit area for the whole of Penmaen Mawr now appears on Ordnance Survey maps as a blank area with ‘Quarries’ written over it, and therefore is devoid of any continuous contour rings, which is the norm for quarried areas on Ordnance Survey maps, with the highest contour line being 350m for the area where the lower easterly peak is.

Therefore this hill’s new summit height is 385.8m (LIDAR data) which is 35.8m higher than its uppermost contour line on current Ordnance Survey maps and its drop is sufficient for it to be classified as a Trichant and 300m Twmpau (thirty welsh metre prominences and upward) hill.

The full details for the hill are:

Cardinal Hill:  Tal y Fan

Summit Height:  385.8m (LIDAR data)

Name:  Penmaen Mawr

OS 1:50,000 map:  115

Summit Grid Reference:  SH 70441 75241

Drop:  31.3m (LIDAR data)

Aled with Penmaen Mawr (SH 704 752) in the background

Myrddyn Phillips (July 2016)

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