OS Triangulation Points

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.

Triangulation Points

I like collecting things. Triangulation points are a favourite along with benchmarks that can be found along a walk or near to one.

There is something very satisfying about reaching a trig pillar, partly I guess because they invariably involve a walk up hill and a reward of sweeping views, weather permitting. There are 84 pillars within the Peak District National Park boundary and many more triangulation points and thousands more benchmarks.

Some are not shown on maps with the traditional blue triangle, the one at Hey Edge for instance, built but never used for triangulation, but was used for levelling, so does it not qualify for the blue triangle.

Some triangulation points are not even pillars. One of my walks takes in the Hunting Tower on the Chatsworth Estate, the triangulation point being the flagstaff. Another is the centre of the spire of All Saints Church in Bakewell.

With the advent of GPS the triangulation pillar network became largely redundant, but a few still do have a purpose. The pillar at Harland South, levelling bracket number 2998 is part of the Global Positioning Network and as such is protected by Ordnance Survey. A plate informs the visitor that any damage should be reported to the phone number.

Triangulation points always come in a minimum of three so a favoured walk of mine takes in the Hunting Tower at Chatsworth, the pillar at Birchen Edge along with the Three Ships and the pillar at Harland South, passing Hobs House, one of the first ancient monuments to have legal protection in the UK, on the way. Two pillars, one part of the Global Positioning System and one flagstaff on a hunting tower. Not bad for a day out.

Trigpoint Walks 7

Moors for the future helicopters on Bleaklow
Moors for the future helicopters on Bleaklow

This walk was a bit like last minute Christmas shopping, recovering my tracks several times, it’s what comes of leaving one triangulation point out on its own. There was another odd thing about this walk, two of the triangulation pillars were not even shown on the map, but did appear in the definitive list, one has almost completely disappeared but the other still sits there all forlorn and unloved. I’d also made the mistake of parking my car in the wrong place, leaving it miles from my first point and my last whilst passing it during the course of the day.

I started off in Old Glossop a village on the edge of the Peak District. I guess its heyday is long past now, the textile, chemical and engineering works now a fraction of their former self.  Glossop is trying to re-invent itself as a gateway to the Peak District and it is well placed geographically to make a viable future on this basis.

I headed across fields to meet up with the Longendale Trail, a 6.6 mile section of the coast to coast Trans Pennine Trail, that runs along the now defunct Woodhead rail line. It is a pleasant walk, with bikers and horse riders all enjoying the easy terrain. The trail follows an old pack horse route that still retains much of its history if you have the time to explore and also leads on to the original Road to the Isles, which must have been a massive journey in the days before the car.

SE 0803 0044 Hey Edge 423m
SE 0803 0044 Hey Edge 423m

I was heading for the last triangulation pillar, Hey Edge, left on the north side of the Woodhead Trans Pennine Road.  This is an odd pillar in more than one sense.  Firstly it does not appear as a triangulation pillar on any OS map, but is denoted as “Pillar” on the OS 1:25000 map.  Secondly it is surrounded by much higher pillars that would have been more use in the survey, so its a bit hard to understand why it was erected, perhaps they got it wrong and found they had put it in the wrong place.

Its a simple walk up from YHA Crowden on the Pennine Way, through old quarry workings and onto a plateau that sits below Westend Moss and looks across to Laddow Rocks and Featherbed Moss.  There are some glorious views from the pillar with wide panoramas stretching far in to the distance.

Head west from the pillar, dropping down into the clough bottom and you pick up The Pennine Way at Crowden, a stopping off point for many long distance walkers on their first day on this classic walk along the spine of England to Scotland.  Follow the trail, crossing the Woodhead road, I told there was much re-tracing of steps, and staying on the Pennine Way ascend Torside Clough towards Bleaklow, heading for the second ford on the OS map facing Long Gutter Edge and Torside Naze. Readers of climbing history will know the significance of these rocks and the part they played in the lives of Manchester climbers in the 60’s particularly Don Whillans and Joe Brown.  The Peak District in general was the birthplace of a new generation of climbers in the post war period.  Working class men and some women, with no real experience of climbing began to put up new, exciting and daring routes along the gritstone edges around the Peak, advancing techniques and skill way beyond the then levels, and leading to many Himalayan conquests in later years.

SK 0593 9618 Cock Hill 427m
SK 0593 9618 Cock Hill 427m

Turn right at the second ford ascending a small gully, following a fence line until a track is reached.  It may well be a noisy walk and do not be surprised to see helicopters constantly ferrying large white bags through the skies.  This is Moors for the Future a government-funded project reversing 150 years of destruction of the moorland habitat. The idea is to return the moorland to its natural wet state full of wild flora and fauna, thereby increasing the production of peat aiding more growth. You may agree with the aims, but rest assured as you sink up to your thighs in the latest peat bog, those thoughts will be the furthest from your mind, so console yourself with the fact you are struggling to get out of a good cause!

SK 0215 9203 own Edge Rocks 411m
SK 0215 9203 Cown Edge Rocks 411m

The final leg led me past the car and over to the other side of Glossop to reach the final triangulation point on the plateau near Cown Edge Rocks. It was a journey through the town and out the other side walking up through horse manured fields with a final short scramble on to the plateau. The biggest problem was finding the remnants of a triangulation pillar that information stated had been removed at the land owners request. Why would you want to do that I wonder, especially when it is in the middle of a field with no real economic value. Doesn’t make sense.

After stumbling around in fading light I eventually found the remains hidden in the grass and was able to call it a day.  The long trudge back to the car was, well a trudge. This was the longest day with 32 kilometres of travel and 1332m of ascent and 9 hours of foot pounding.