Tuesday 25 April 2017

Mapping Mountains – Trimble Surveys – Cilfaesty


25.03.17  Reilth Top (SO 284 881), Colebatch Hill (SO 292 874) and Bryn Hill (SO 295 862)

Colebatch Hill (SO 292 874)

The Shropshire hills can give a tranquil experience, especially so under seemingly never ending blue sky with distant views and hour after hour of solitude.  Today I wanted to test my wonky right knee with something more than just one small hill, so I opted to join three small hills together and try and time my completion for a 6.00pm – 7.00pm arrival at Clun YH to join the evening’s festivities at the annual Triggers meet.

I parked beside a no parking sign on a large patch of muddied road leaving sufficient access in all directions to all gate and drive entrances, and headed up a delightful green track toward the summit of my first hill of the day; Reilth Top.  Heading up the track the sun cascaded out of a deep blue sky and the slight chilled late March morning added to the freshness of early spring warmth.

The summit of Reilth Top is in a closely cropped grassed field with a covered reservoir in its corner, as I gathered the first of what proved to be three data sets from the area of this hill’s summit two walker’s approached, I waved and heading my way were Richard and Denise Mclellan, I’d corresponded with Richard via email in the past and was a friend of Denise’s on Facebook, but this was the first time that I had met them.  We chatted for ten to fifteen minutes as the sun shone and the Trimble gathered the first of its three data sets.  They had walked from Clun and were heading down for lunch followed by the walk back to the Youth Hostel, and had come over the hills that I planned on visiting later in the day, so I checked on the route ahead.  As they waved their good buys I set the Trimble up to gather its third data set and once complete, closed it off, packed it away and headed down to the col connecting Reilth Top with Colebatch Hill.

Gathering the first data set on the summit area of Reilth Top

Denise and Richard Mclellan

Gathering data at the summit of Reilth Top

I’d come prepared with a number of 10 figure grid references for each summit and col and had been told by Richard that the connecting col looked as if it was positioned in a paddock which had horses in it, this wasn’t ideal.  However, when I arrived near the col I thought the critical point to lay next to the paddock and wondered if I could sneak in to land behind a large barn and gather five minutes of data without being disturbed, so I crept through a gate and wandered around a bit looking at the grid reference on the Trimble’s screen and at the same time trying to assess the lay of land which looked relatively flat, it was then that I spotted a figure heading toward me, he didn’t really ask me what I was doing, but his mannerisms did, so I explained anyway.  He thought I’d better explain to the person at the adjacent Vron Farm, so off we both marched, a few minutes later and the woman at the farm had given me permission to take data from wherever I wanted, it so happened that the point I decided to gather data from was in the adjacent land between the paddock and the farm’s and which was owned by the person who had first approached me.  I set the Trimble up and stood back once it was activated, a few minutes later and the same person came down toward me again looking inquisitively at what I was doing but asking few if any questions, I mesmerized him with Trimble figures and smiled a lot which seemed to help, and then packed the equipment away once it had gathered five minutes of data, thanked him for his time and walked toward the connecting footpath toward Colebatch Hill.

Gathering data at the col area of Reilth Top

I initially followed the public footpath that contours round the northern part of Colebatch Hill, before leaving it to follow a hedge line direct up the hill toward the manicured green field where the summit is situated.  I spent a few minutes assessing the lay of land from different directions before choosing the spot for Trimble placement.

Gathering data at the summit area of Colebatch Hill

Below to the south lay my next objective, the connecting col between Colebatch Hill and Bryn Hill, however this was positioned in a field between two houses so I thought the wisest approach would be to ask permission to visit, leaving the summit behind I wandered down the southerly slopes and skirted woodland on its east before finding a metalled gate leading to a path through the front of what looked like a small holding, this led onto the gravelled track heading down from the house to the minor road in the valley beyond, toward the end of the track were two people busy at work erecting large poles in the ground.  I stopped and chatted and explained what I hoped to do and asked if I could head in to the adjacent fields.  Permission was duly granted and I was directed through the grounds of the next house which was a holiday home which wasn’t occupied this weekend, this gave me peace of mind and I contentedly made my way up the field and through the gate to the property and then down the access track toward the field and the connecting col.

This col proved a quiet affair with just an occasional vehicle chugging its way over the lane above me whilst the sheep grazed and the Trimble slowly ebbed down to its 0.1m accuracy level before data should be logged, once this was attained I pressed ‘Log’ and stood back for the allotted five minutes of data to be collected.

Gathering data at the critical col of Bryn Hill

Heading up the field to a gate I followed a forestry track in to Blakeridge Wood which swamps the eastern side of Bryn Hill.  I followed this track for quite some time and decided to head back to the lane when it started to go downhill and lead away from the summit.  By doubling back it gave me over a mile of unnecessary walking which isn’t much in the grand scheme of things but I didn’t want to overtax my right knee, so this proved an unwelcome addition to the days exertions, but being on the forestry track gave me views northward toward the Stiperstones, which is one of the undoubted highlights of the Shropshire hills.

Distant view of the Stiperstones

Getting back on to the lane was a relief but I now had to descend over 40m in height as I followed the lane down through the quiet surrounds of Cefn Einion.  I then branched left on the continuation of the lane to a track which gave me access to a gate and the steepening western slopes of Bryn Hill.  Field after field and gate after gate led me up to the summit which is situated in the field adjacent to the forestry that I’d backtracked out of an hour or so ago. 

House front in Cefn Einion

I took two data sets from the summit area of Bryn Hill, one on ground beside a small covered reservoir and one where I judged the high point to be in the field leading toward the forest.  Once data were stored I packed the Trimble away and headed down the hill, only stopping to take photos of a delicate cloudscape toward the south as pink tinged high cloud wisped through the sky.

Gathering data at the summit of Bryn Hill

Delicate cloudscape from Bryn Hill

I arrived back at my car after a mile or so of walking on the country lane, by now the sun had sank behind the hills to my south-west, and I changed in to clean clothes as the first chill of evening crept down on the land.  It was only a short drive to Clun and its Youth Hostel for an excellent evening of good company, good conversation, excellent food at a very reasonable price (£3.50 for main course and three puddings) and a talk by a self-employed surveyor who used to work for the Ordnance Survey, a good end to an excellent day.


Postscript:

Since the survey of these hills full LIDAR coverage is now available.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height and positional data that is now freely available for England and Wales.  Consequently the numerical details for these hills have been analysed using this technique, resulting in the LIDAR height and position for some of these hills being prioritised over that produced by the Trimble GeoXH 6000.



Survey Result:



Reilth Top

Summit Height:  404.6m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 28458 88105 (Trimble GeoXH 6000) (summit relocation)

Col Height:  375.4m (LIDAR)

Col Grid Reference:  SO 28878 87840 (LIDAR)

Drop:  29.2m (Trimble GeoXH 6000 summit and LIDAR col) (Four reclassified to 400m Sub-Four) 

Dominance:  7.22% (Trimble GeoXH 6000 summit and LIDAR col)





Colebatch Hill

Summit Height:  415.9m (LIDAR)

Summit Grid Reference:  SO 29215 87470 (LIDAR)

Col Height:  318.6m (LIDAR)

Col Grid Reference:  SO 28961 88784 (LIDAR)

Drop:  97.2m (LIDAR)

Dominance:  23.38% (LIDAR)





Bryn Hill

Summit Height:  407.5m (converted to OSGM15)

Summit Grid Reference:  SO 29550 86222 (summit relocation)

Col Height:  298.9m (converted to OSGM15)

Col Grid Reference:  SO 29299 86584

Drop:  108.6m

Dominance:  26.64%


 









1 comment:

Rob said...

Hi, I notice on a lot of the photos using the Trimble it is sitting on top of a rucksack. Do you take accurate measurements of the rucksack height above the ground to account for this? Where on the device is the reference point for the exact altitude being measured?