Thursday, 11 January 2018

Mapping Mountains – Trimble Surveys – Pumlumon


29.10.17  Gallt y Gog (SH 751 012)

Gallt y Gog (SH 751 012)

Gallt y Gog is a conifered summit that looks horrendously wooded from a distance but which proved easily accessible.  It rises on the northern periphery of Machynlleth and looks down on the town which nestles beside the Afon Dyfi as it continues its downward flow to the coast.

I got lost trying to find where I wanted to start the walk from, and asked directions having driven up a road beyond a housing estate.  I was directed up a near road with pre-warning that it was rough and that it led to a number of houses, its description as ‘the high road’ sounded good, as even though this hill is not great in height the higher the better for my starting point.

I found a parking place beside two cars next to one of the houses and continued up the rough road after spotting a dead Robin on the grill of my car, it was spread like a trophy, its poor little legs dangling down from its feathered breast, with its head trapped in the grill.  I levered it off and gave it an improvised burial before continuing up the rough road.

An unfortunate consequence of driving

The road led past another house before contouring around a bungalow and near barn before what seemed to be the last house on its journey.  This rough road led up and around the north-east of the hill and continued around the northern part of the summit, which bulged up before me in planted conifers.

I left the road to walk over a field toward the forest’s perimeter fence which was conveniently collapsed above steep ground, when in the wood a narrow path led beside the perimeter fence to a small bench, to my right and amongst the conifers was the summit and the ground between me and it looked horrendously brambled, I hoped that a path led from the bench to the area of the summit, and thankfully one did.

It was only a short walk to the high point from beside the bench, over one felled tree and beside a mass of unwelcoming brambles.  The summit is close to a concrete and graffitied structure that looks decidedly at odds with where it is placed. 

The concrete structure near the summit of Gallt y Gog

The Trimble was soon set up and after a short wait I activated it to gather data, as it quietly beeped away collecting its minimum of 300 allotted datum points the sun occasionally broke through high cloud casting extended shadows through the trees, otherwise all remained quiet in the wood.

Gathering data at the summit of Gallt y Gog

Once I closed the Trimble off and packed it away I retraced my route back to the bench and out of the trees and down the road to my car.  I then drove down the rough road back through the housing estate and on to the A 489 road and east heading out of the town stopping beside a track giving access toward the town’s golf course where the critical bwlch of Gallt y Gog is placed.

I’d assessed this spot using OS Maps and a Google car and had enough space to reverse my car on to the pavement and yet for the Trimble when placed on the roof of my car to still be aligned with where I deemed the critical bwlch of this hill to be positioned.

Gathering data at the critical bwlch of Gallt y Gog

I quickly measured a 1.45m offset to the road below and activated the Trimble when the 0.1m accuracy level had been attained and stood away from my car as a multitude of vehicles past it heading this way and that.  I’ve learnt my lesson with roadside surveying and if it’s safe to do so it is always best to position the Trimble on top of the car roof.

Once five minutes of data were stored I closed the equipment off, packed it away and headed off to survey the critical bwlch of Coed Pant y Glo before continuing my journey home.    


   
Survey Result:


Gallt y Gog

Summit Height:  87.5m (converted to OSGM15) (significant height revision) 
 
Summit Grid Reference:  SH 75169 01223

Bwlch Height:  24.8m (converted to OSGM15)

Bwlch Grid Reference:  SH 75569 00923

Drop:  62.7

Dominance:  71.68%







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