Saturday 23 September 2017

Mapping Mountains – Hill Reclassifications – Y Trichant


Penmaen Mawr (SH 698 755) Sub-Trichant addition

There has been an addition to the listing of Y Trichant initiated by a survey with the Trimble GeoXH 6000, with subsequent confirmation through analysis of LIDAR data by Aled Williams.  Y Trichant is the title for the hills in the 300m height band of the Twmpau (thirty welsh metre prominences and upward) and takes in all Welsh hills at or above 300m and below 400m in height that have a minimum 30m of drop, with the introduction to the re-naming of this list appearing on Mapping Mountains on the 13th May 2017.

The details relating to this hill’s addition as a Sub-Trichant are retrospective as its new classification was dependent upon a survey with the Trimble GeoXH 6000 which was conducted on the 14th July 2016.

The hill did not appear in the sub category that accompanied the original Welsh P30 lists when published on Geoff Crowder’s v-g.me website, this sub category has now been standardised and named the Sub-Trichant and comprises all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.

The hill was not classified prior to the survey with the Trimble as much of the hill has been quarried and as is the norm in such circumstances there is a lack of uppermost contour lines on current Ordnance Survey maps.  But at one stage it was a part of a relatively substantial hill that had a prominence in excess of 100m and a 1,550ft (472m) summit map height shown on the Ordnance Survey Popular and New Popular One-Inch maps, with this height also appearing on the Ordnance Survey Six-Inch map published in 1888, and therefore it would have met the criteria specified for inclusion to the Humps and the main Y Pedwarau listings.  The subsequent quarrying has produced two distinct summits with the details given in this post relating to the higher of the two summits that are both known by the same name.  The hill no longer meets the qualification for these two listings as its summit has been quarried and current Ordnance Survey maps only give it an uppermost 370m contour line.  However, quarried areas are usually given no contour lines on Ordnance Survey maps indicating that the ground is or has been in flux, and photographic and map study by Aled indicated that the remaining high point was substantially higher than 370m.

The name of the hill is Penmaen Mawr and it is a part of the Carneddau range with its Cardinal Hill being Tal y Fan (SH 729 726) and is placed in the Region of North Wales (Region A, Sub-Region A1).  The hill is situated to the south of the A 55 road and is positioned between the towns of Llanfairfechan to its west and Penmaenmawr to its east, with the latter taking its name from the hill.

The hill can be easily accessed from a minor road to the south of the summit that reaches over 260m in height, a public footpath heads north from just below the high point of this minor road and joins a track designated a bridleway that contours around the southern slopes of the upper section of the hill.  A large section of the land above the bridleway is designated open access land and the summit of Penmaen Mawr is close to this.



The full details for the hill are:


Cardinal Hill:  Tal y Fan

Summit Height:  390.4m (converted to OSGM15)

Name:  Penmaen Mawr

OS 1:50,000 map:  115

Summit Grid Reference:  SH 69865 75523
  
Drop:  26.9m (converted to OSGM15)


Penmaen Mawr (SH 698 755) is now included in the listing of Sub-Trichant hills



Myrddyn Phillips (September 2017)






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