Showing posts with label Mynydd Llwydiarth. Show all posts
Showing posts with label Mynydd Llwydiarth. Show all posts

Monday, 29 March 2021

Mapping Mountains – Hill Reclassifications – 100m Twmpau

 

Mynydd Llwydiarth (SH 545 791) – 100m Sub-Twmpau addition 

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Mynydd Llwydiarth (SH 545 791)

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Mynydd Llwydiarth, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north, minor roads to its west and east and the B5109 road to its south, and has the village of Llanddona towards the east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 22m of drop, based on an estimated c 155m summit height and an estimated c 133m bwlch height, the latter based on interpolation of 5m contouring between 130m – 135m that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

However, it was not until LIDAR became available that the 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. 

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 156.1m summit height and a 132.6m bwlch height, with these values giving this hill 23.5m of drop which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Mynydd Llwydiarth 

OS 1:50,000 map:  114, 115 

Summit Height:  156.1m (LIDAR) 

Summit Grid Reference:  SH 54519 79147 (LIDAR) 

Bwlch Height:  132.6m (LIDAR) 

Bwlch Grid Reference:  SH 54380 78960 (LIDAR) 

Drop:  23.5m (LIDAR) 

 

Myrddyn Phillips (March 2021)

 

 

 

Sunday, 17 March 2019

Mapping Mountains – Trimble Surveys – Mynydd Twr


22.10.18  Mynydd Llwydiarth (SH 541 787)  

Mynydd Llwydiarth (SH 541 787)

Mynydd Llwydiarth is positioned in the south-eastern part of Ynys Môn and is one of only a few forested summits on the island.  The Hill Bagging website give some formidable write-ups with many mentioning copious amounts of brambles, fallen trees and a confusion of undergrowth, with one post in particular standing out when David Gradwell became so entangled that he had to use pruners to cut himself free, however one post tantalisingly mentions a faint path.

The summit area of the hill has a trig pillar that many head out to find, but do not get there.  It also has a lump within the summit area that is recognised by hill baggers to be the high point, this is approximately 100 metres north-east from the difficult to find trig pillar.  Between these two is another lump that LIDAR gives as the true summit.  My main purpose was to visit at least one of these two summit positions and gather Trimble data from it, and if possible retreat from the upper confines unscathed.

I parked as many had done before at the entrance to the forest beside a minor road at the start of a gated forest track; this led in beautiful autumnal sunshine upwards zig-zagging as it went under a large crag.  As the track neared its highest point a minor track heads eastward from it, I followed this and started scouring the woodland on my left for any sign of a path.  Miraculously I found one!

The start of the forest track

Heading toward the brambles

The path led confidently in to the undergrowth and proved an absolute delight compared to what was beside it, which consisted of a mass of brambles, scrub and fallen trees.  The latter did appear on the path but all could be easily stepped over.

This narrow path leads toward the summit that was Trimbled

Bit by bit the path slowly led through the forest toward a mound that emerged out of the undergrowth, this had to be one of the summits.  As the path neared the mound it became narrower to the point that toward the base of the mound it disappeared, I then tried to memorise the trees beside the path for my outward journey, to try and memorise what a tree looks like in a forest is somewhat foolhardy!

Once I’d scrambled to the top of the mound I found what I judged to be its high point and set the Trimble up to gather data.  It achieved the 0.1m accuracy level before data should be logged relatively quickly considering its position and I then spent the next ten minutes standing in scrub beside one of many trees out of its direct line of site.

The view from the summit that was Trimbled

My view from the summit that was Trimbled

After ten minutes of data were gathered I packed the equipment away and started my outward journey, remembering the way I had approached, or so I thought.  Within a matter of minutes any semblance of a path was long forgotten and I then spent an inordinate amount of time battling through an amazing amount of brambles, fallen trees and hazardous undergrowth beyond belief.  Oh the contrasting nature of forested summits with such an easy ascent followed by investigating the inner realms of bramble heaven!

Gathering data from one of the Mynydd Lwydiarth summits

Investigating the forest

Eventually I emerged back on the minor forest track that led to the wider track where I met another human being, this seemed odd as I thought I was the only person in the world, or so it seemed whilst battling through the brambles. 

The other human was out for a walk up the track, we stopped and chatted for a few minutes before I continued down to my awaiting car relieved that I’d bagged at least one of the Mynydd Llwydiarth summits and also gathered all-important Trimble data from its high point.  I wonder if I’ll ever return to try and find the other summit.    



Survey Result:



Mynydd Llwydiarth 

Summit Height:  158.1m (converted to OSGM15, Trimble GeoXH 6000) (LIDAR summit:  158.5m)

Summit Grid Reference:  SH 54126 78707 (Trimble GeoXH 6000) (LIDAR summit:  SH 54083 78685)

Bwlch Height:  100.5m (LIDAR)

Bwlch Grid Reference:  SH 55284 79340 (LIDAR)

Drop:  57.6m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  36.45% (Trimble GeoXH 6000 summit and LIDAR bwlch)