In the 1700’s the first baseline for triangulation was measure on Hounslow Heath. It first used wooden then iron and finally glass rods for better accuracy to measure the baseline of the first triangle. Subsequent triangulations formed new baselines, then in 1936 a whole new system of triangulation was developed by Ordnance Survey along with a whole new set of markers on the ground for the triangulation points.
The last triangulation of Britain took place between 1935 and 1962 with the now familiar triangulation pillar being used for the first time. Along with the pillars there were several other types of markers employed for the survey points.
Buildings were often used, especially ones which would not probably be pulled down in the future, churches were a favourite, Bakewell was one, as was the Hunting Tower and its flagstaff on the Chatsworth estate.
Fundamental Benchmarks were the cornerstone of the whole system, these were protected by iron fencing. The FBM as they were known were seated on bedrock and were used as definitive levelling points as the one on the Mortimer Road on Broomhead Moor.
Surface Blocks like the one at Hollingworth Head, there is also one near Big Moor formed part of the triangulation measurements. They lie close to the surface but are hard to find as they are often covered with grass. Even harder to find are Surface Bolts such as the Laddow Rocks one. It is amazing that a small bolt has survived all this time.
And sometimes a triangulation point just isn’t one. This is the case of the Hey Edge Pillar which is marked on the map as a Pillar, but does not have the blue triangle on the map. That is because whilst it was built it was never used for triangulation. It was used for levelling, but as I have said that is a totally different set of measurements. Hence it does not qualify as a trig point to Ordnance Survey.
Nowadays with GPS triangulation by hand is no longer required and the Ordnance Survey network of triangulation points is falling in to disuse, apart from a few that is. The Triangulation Pillar at Harland South forms part of the Global Positioning System network, as does the Fundamental Benchmark on Broomhead Moor. So even though GPS is now the dominant measuring system for position, it still relies on spots on the ground for accuracy.
This is a levelling benchmark placed and used by Ordnance Survey. Its location is SK 2305 8759 at Moscar on the footpath from the A57 towards Stanage. The mark was made in 1961, is of the third order of surveying and is 600mm above ground level. Its datum is Newlyn. Originally the mark and boulder were on the west of the footpath but time and boots have now placed it east of the path.
There are some 500,000 benchmarks on the UK mainland, most no longer in use. They identify the height at a given point. The base line is the tidal measuring station at Newlyn in Cornwall, that is the point where all height measurements are taken from, including the 190 Fundamental Benchmarks which were the first order and therefore the most accurate, set in chambers deep underground on bedrock , these benchmarks are still in use today by the Global Positioning System for calculating the accuracy of the height calculation.
Every Christmas when I was a kid mom and dad would drag my brother and I across town to visit Uncle Frank and Aunty Iris. It was a walk of 3 miles or more through suburban housing and odd open spaces. We walked because we didn’t have a car, this was back in the sixties and walking wasn’t a pastime then, it was how you got about.
I looked forward to the walk because when we got to the Colin Campbell pub we had to cross some open land, that had a pond with stickleback fish in, weird dry grass and even more strange black hills about twenty feet high. It was a very odd place. I now know it was an old coal pit, closed long before that whore of the city Thatcher got her hands on the school milk, never mind whole mining communities.
In one corner was this sinister obelisk. It stood on one of the small hills, like a pyramid, the white bright against the black coal spoil. It always freaked me out a bit because it sat there throbbing, a deep hum seemingly emanating from the inner core. Of course this was in the days of the first Dr WHO programmes which I watched from behind the settee so perhaps it could have been my imagination. I always looked out for the pyramid but never thought to ask what it was. Such are the seeds of a future life wasted on trivialities and other such important stuff in life.
The latest triangulation walk covered ancient routes, astronomy, the global positioning network and the legacy of the privileged classes, quite a menu for a days walk.
Rain has been a constant companion for quite a lot of us lately, I see they are now calling the current weather a conveyor system, a pretty descriptive term as we seem to be getting massive pulses of rain interspersed with a day or so of cold blue skies. I had not chosen one of the blue sky days, more to the pity. At least it didn’t bucket it down or freezing cold.
The first trig was at the top of a hill, so no surprises there then. To get to it I had to walk up through two villages, first Low Bradfield and then High Bradfield along a lovely old stone paved trail, the gritstone slabs dished with hundreds of years of passing feet. At High Bradfield a sign told me the church was open but as I vigorously rattled the door like one of Henry’s boys from the monastic cleansing department, it clearly wasn’t. Peeved me a bit that did as I wanted to use the porch to put on my waterproofs, as it was I had to don them beside an opened stone coffin which thankfully only contained an empty crisp packet, salt and vinegar flavour, and a chocolate bar wrapper.
Onwards and upwards through the most sodden ground I have seen in a long time. There has been so much rain the ground cannot take any more. Water sits in great lakes across the landscape, cascading off fields and down roads in sheets of rippled silver.
Kirk Edge trig point is pretty un-glamorous surrounded by grotty fields, a water board pumping station and broken down walls. The view wasn’t even any good today as you can see. There is some compensation though in the rather sinister and newly refurbished buildings to the east. These belong to Sheffield University Astronomy department. I have no idea what they do up there, but it does bring back similar feelings to my childhood forays to Aunty Iris.
Onwards then to a special trig via Rocher Edge a wonderfully isolated wooded area with towering cliffs just asking to be scaled. My goal was a very special triangulation point, so special it had a special fence and a plaque.
This strange trigpoint is still in use as part of the GPS system today. The picture at the top of the blog is of the top of the stone obelisk shown here. It is odd isn’t it that today’s GPS hi-tech units still have to rely on a piece of technology built in the thirties. It is called a Fundamental Benchmark because it was one of the first trigs established and is set on bedrock so is highly unlikely to move and therefore very reliable.’
Lunchtime and I found a sheltered spot from the wind and rain along a shooting track that led onto the moors. It was quite a nice place, I was very comfy with my flask and pot of noodles, I rather enjoyed myself.
The final trig was only about 750m away from me but I decided to avoid the steep clough, didn’t fancy clambering down and back up again in all that wind and rain. I followed the track round then turned east before cart wheeling head first in to a peat bog, the first of three that day. It is a part of Peak District moorland walking, peat bogs, and you just have to accept that at some point you will be sucked in. There’s one born every minute as Sam used to say.
This was my little bit of nav practice in a howling gale with just the use of the map. My objective was marked on the OS map as “New Cross”, which sat on a small featureless plateau. I focused on a point on the skyline and headed for it through thick heather, peat grough and waterlogged marsh land, arriving bang on the cross with no time wasted looking for it.
I am unsure what the crosses were for, there are a few of them in the Peak district and I assumed they were some form of ancient way markers. They always have a base where the post must have fitted, but is now long gone and always in a remote location in relation to today’s transport routes. They do warrant further study, perhaps they were a form of trig point, albeit without the triangulation.
A simple bearing and some pacing took me across moorland to the final trig on a small hill over looking the Bradfield Valley.
The light was starting to fade now, time to get off the hill and out of the wind and rain. As I headed back to the village the rain softened, big drops landed gently on my coat and made for a pleasant end to the day.