Mapping Mountains – Trimble Surveys – Y Garn

25.05.23  Esgair Llwyn Gwyn (SN 885 790) 

Esgair Llwyn Gwyn (SN 885 790)

Out with Mark Trengove today visiting a Pedwar to the west of Llangurig, which is one of only a few Pedwarau in the northern part of Mid Wales that I had until today not visited.

For me it was a relatively late start as it was past 3.00pm when we set off from the car park on the southern periphery of the small village of Llangurig.  The predicted high cloud soon pushed in over the land, the hills remained clear, but the dry heat of recent days was now replaced with mugginess. 

Llangurig

Our route followed the course of the Afon Gwy (River Wye) on its southern bank for a few minutes before the bridleway leading up the eastern ridge of Esgair Llwyn Gwyn veered south-westward and gradually gained height.  Except for a few people walking beside the river the only other people we saw during the afternoon were a couple descending the ridge close to Llwyn-gwyn farm who were doing a part of the long distance Wye Valley Walk.  We stopped and chatted for a few minutes before continuing uphill. 

Mark heading toward Llwyn-gwyn farm

The outskirts of Llwyn-gwyn farm

Nearing the summit of Esgair Llwyn Gwyn the manicured green of grazing fields gave way to the reed grass and moorland surrounds of the upper hill.  We were soon on the summit wandering around trying to discern its highest point for Trimble placement; LIDAR analysis give three summit positions of equal height, all within a few metres of one another.  Having chosen the spot for Trimble placement I set the equipment up to gather data. 

Nearing the summit

The last bit of uphill

The summit area of Esgair Llwyn Gwyn consists of patches of rough grass and high reed grass, for such examples I usually prioritise the Trimble result over that of LIDAR, as comparison of results show the latter consistently higher than the former; implying difficulty with the LIDAR model when encountering tussock grass and reed grass. 

Gathering data at the summit of Esgair Llwyn Gwyn

LIDAR image of Esgair Llwyn Gwyn (SN 885 790)

During data collection Mark headed toward a trailer where he happily sat for a bite to eat.  I joined him once the Trimble had gathered and stored data.  We chatted and laughed as I sat on a part of the trailer which made it move similar to a swing, with the whole thing moving up and down with the slightest movement. 

Heading down toward the bwlch

Leaving the summit surrounds Mark used his hand-held GPS to head down to the connecting bwlch with the ten figure grid reference produced via LIDAR zeroing us in to the critical point.  However, once we were down near the bwlch we headed toward where we thought the critical point lay without the aid of the grid reference produced by LIDAR.  Once there we then consulted the grid reference, we were about 10 metres away, which proved a good estimate considering the area of the bwlch and its surrounds. 

Gathering data at the bwlch of Esgair Llwyn Gwyn

As I set the Trimble up atop my rucksack and noted the offset between its internal antenna and the ground at its base, before creating the file for data collection and once the 0.1m accuracy level was attained before data should be logged, I set it to gather data and watched as Mark headed through the reed infested mayhem of the bwlch toward a lone small tree before hopefully continuing toward what we planned as our descent route via the Pant Gwyn Hill ridge.  As Mark headed in the direction of greener ground and our path leading to the ridge he veered leftward and continued down through the tussock laden bog of the bwlch.  I wondered what he was doing, and only found the reason for this once I had packed the equipment away and stumbled my way through the tussocks and bog down toward him. 

Through the bog

The reason for continuing down through the bog instead of heading toward our planned path and descent route was one of a barb wired fence.  These pests are getting harder to cross as I am getting older.  The older fences I can stride over, but the newer taunt ones require climbing, which nowadays I do not enjoy.  Mark now has a pair of dodgy knees and barb wired fences are something to definitely avoid and I’m afraid one of these stretched across our planned onward route and necessitated a diversion down through copious amounts of reed infested bog. 

The expanse of bog and rough ground at the bwlch

Eventually the bog was overcome and we reached drier and easier ground.  As Mark headed up to a section of collapsed fence, I continued to contour using what looked like an old water course, this headed toward a wood which gave variety to our unplanned descent route.  We met at the far side of the wood. 

Looking back toward the bog from just within the wood

All that now remained was a slow wander back in the early evening light down our inward route past the farm of Llwyn-gwyn and the continuation of the track beside the river and the small section on the minor road leading to the car on the outskirts of Llangurig. 

Nearing the end of the walk

We rounded the day off with an excellent meal in The Raven in Welshpool, which gave a welcome last couple of hours to enjoy good food and continued good conversation; it proved a fine way to end an excellent day. 

 

Survey Result:

 

Esgair Llwyn Gwyn

Summit Height:  435.9m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SN 88577 79070

Bwlch Height:  402.3m (converted to OSGM15)

Bwlch Grid Reference:  SN 88120 78849

Drop:  33.6m

Dominance:  7.71%

 

 

For further details please consult the Trimble Survey Spreadsheet