Saturday, 23 January 2016

Mapping Mountains – Significant Height Revisions – 100m Twmpau


Bryn Maelgwyn (SH 795 805)

This is the twenty fifth post under the heading of Significant Height Revisions, with the Trimble survey that resulted in this height revision being conducted on the 16th January 2016.

The twenty fifth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the north-western part of the Rhos range of hills that is connected to Gogarth (Great Orme), above the town of Llandudno.

The hill was surveyed in the company of Alex Cameron during a grey and damp day when we visited five P30 Twmpau hills over four separate small walks, with each summit being Trimbled.

The hill is listed in the 100m Twmpau (thirty welsh metre prominences and upward) list, and it has a 105m uppermost contour ring on the Ordnance Survey enlarged map on the Geograph website, which has contour intervals at 5m.  The hill has been listed with an estimated height of c 106m based on the dimensions of the uppermost contour in relation to the steepness of the surrounding ground.

The hill can be accessed from its south where a public footpath enters the Coed y Gell woodland.  However, to reach the summit one has to leave this footpath and the going thereafter becomes rougher with brambles and bracken creating a tangled web of undergrowth.  When I visited with Alex the underfoot conditions were never difficult and as the deciduous trees are growing relatively far apart from one another there are sufficient gaps in between to make good progress toward the summit.

The name of the hill is Bryn Maelgwyn and prior to the survey with the Trimble GeoXH 6000 the height of the hill was estimated as being c 106m based on 5m contour intervals on the Ordnance Survey enlarged map on the Geograph website, and to my knowledge no spot height has ever appeared on an Ordnance Survey map for this hill.

Therefore this hill’s new summit height is 102.1m (converted to OSGM15) which is 3.9m lower than its previously estimated height of c 106m and 2.9m lower than its uppermost ring contour on the Ordnance Survey enlarged map on the Geograph website.


The full details for the hill are:

Cardinal Hill:  Gogarth 

Summit Height (New Height):  102.1m (converted to OSGM15)

Name:  Bryn Maelgwyn

OS 1:50,000 map:  115

Summit Grid Reference:  SH 79580 80540 
         
Drop:  c 39


Gathering data from the summit of Bryn Maelgwyn which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (January 2016)