Before GPS made everything frictionless, Ordnance Survey needed fixed, precise reference points across the entire country to triangulate accurate maps. So between 1936 and 1962 they built 6,500 of them. Concrete pillars, about a metre tall, placed across Britain wherever the surveyors needed them. Hills, moorland, clifftops, the occasional suburban park, a salt marsh, and in at least one case, 0.5 metres below sea level. They called them triangulation pillars. Everyone else calls them trigs.
GPS made them obsolete in the 1980s. Ordnance Survey decommissioned the network. And then, quietly, people started hunting them anyway.
"Most trig points are on high ground. Which means getting to one often involves a climb, a view, and standing somewhere that most people driving past on the road below have never been. The trig is an excuse. The landscape is the point."
Why bother?
This is the question that makes non-trig-hunters look slightly baffled. They're concrete posts. In fields. Often in the rain.
But here's the thing. Most trig points are on high ground, that's the nature of triangulation. Which means getting to one usually involves a climb, a view, and standing somewhere that most people driving past on the road below have never been. The trig is an excuse. The landscape is the point. Though for the record, the lowest trig in Britain sits 0.5 metres below sea level, which raises questions about the walk there that we'll leave to your imagination.
There are 6,500 of them. Some people are trying to find all of them. This is called bagging. It is, objectively, a mild form of madness. It is also completely brilliant.
How to start
You don't need much. Decent footwear, an OS map or the OS Maps app, and the TrigpointingUK website or app, which logs all 6,500 with GPS coordinates, photos, condition reports and a record of who's visited. You can log your own visits. The mild competitive satisfaction of watching your count go up is part of the deal.
Start local. There are trigs within a few miles of most people reading this. Find the nearest one, walk to it, put your hand on the cold concrete, look at the view, and see if you get it. Most people do.
Find the nearest one, walk to it, put your hand on the cold concrete, look at the view. Then see if you don't immediately start looking for the next one.
- Download the TrigpointingUK app before you leave. It holds all 6,500 locations with GPS coordinates, photos and condition reports. You can log each visit and watch your count grow.
- The OS Maps app is worth the subscription. Paper 1:25,000 maps work equally well and feel considerably more satisfying to fold incorrectly in a strong wind.
- Start with the nearest one. Don't plan a pilgrimage for your first trig. Find the closest one, walk to it, see how it feels. The obsession develops on its own from there.
- Check the condition report before you go. Some trigs are pristine. Some have been damaged, buried or lost entirely. The app will tell you what to expect.
- Log your visit. The TrigpointingUK community records who's been to each pillar and when. You are, in a small way, becoming part of the history of that particular piece of ground.
What to take
Nothing elaborate. The point is the simplicity of it. OS Maps app or a paper 1:25,000 map. A flask. Layers, because the top of a hill can catch you regardless of what the forecast said. A camera, because the light from high ground is different and you'll want to remember it.
Some trigpointers carry a personal stamp, logging their mark in the small logbooks occasionally left at popular trigs. This is optional, but deeply satisfying if you're the kind of person who enjoys a ritual.
A note on condition
Some trigs are pristine. Some have been vandalised, cracked, or buried under years of vegetation. Part of the ritual is checking the condition and logging it on TrigpointingUK. You become, in a small way, the custodian of something that's been standing on that piece of ground since before your parents were born.
The people who do this
We put a call out on Instagram asking trig baggers to tell us why they do it. The response was immediate and enthusiastic, which tells you something about the community. Here are three of the people who got in touch.
"I started trig hunting in 2023 thanks to Instagram. I became immersed in the outdoorsy community on social media, saw people bagging trigs and thought I might try to find one on my next hike. That quickly became an obsession for concrete pillars and I've bagged 125 across the country so far, with plenty of repeat visits to favourites.
They give me focus when I'm planning routes, and I've explored so much of my local area because I've been seeking them out. They're a literal pillar of continuity in the ever-changing landscape, and it's like a collecting hobby I don't have to bring home with me.
It's hard to pick just one favourite, but I'd say either Chanctonbury Ring or Skomer. Chanctonbury is my favourite local place, full of history, folklore and views, so having a trig point there is the icing on the cake. Skomer because it's so pretty, sitting on top of a big rock formation and surrounded by flowers in a really wild and remote place."
"I started my trig point journey roughly three years ago. I'm based in the Peak District, literally surrounded by them. I can see a trig point from my back garden.
My favourite thing about trig points is that they mark an achievement. Climbing a hill or a mountain. Two years ago I gained my NNAS Silver, the National Navigation Award, learning to navigate with a paper map and compass. Bagging trig points was a huge part of that journey. I plotted my own routes and often planned them specifically to include a trig point.
I've met many people through hiking and now have a group of very special friends who make it their mission to bag as many as possible. My Cavachon Rusty has been coming on adventures with us for nearly eight years and has bagged more trigs than most humans I know. We've been to Snowdonia, the Lake District, the Peak District, and hope to venture to Yorkshire next.
My favourite is one close to home called Revidge. It has 360 degree views including Thor's Cave and, on a clear day, as far as Mam Tor. When the heather flowers in August it's surrounded by a carpet of purples. It's my happy place.
I do have close contenders. Wolfscote Hill taunted me for years. Permissive access had only recently been granted, so I'd referred to it as The Unobtainable One. The trig on top of The Old Man of Coniston is also very special. It was my first Lake District trig, on a day of beautiful clear skies.
Standing next to a trig point is unlike standing anywhere else. They have given me inspiration to learn how to navigate. To make memories with family and friends. To look to the future as we plan more adventures and tick more off the list."
"I've been doing this since I was a toddler. My dad used to take us. I've got a book to do all the trigs in Dorset. There are some in really odd and hard to get to places, but the best ones are the ones with a clear view.
When you stand on the top and put your arms out wide, your head back, close your eyes and feel the wind on your face. Magical.
They aren't just a concrete post. They are a destination. A point on the map. A tower to see from. A beacon of nature, wilderness, escapism and the great outdoors.
Even when I walk local and pass a trig I see all the time, I still have to put my hand flat on the top."
Go find one this weekend
The best reason to go outside is always the next one you haven't been to yet. Find your nearest trig on TrigpointingUK, put it in your maps app, and walk to it this weekend. Put your hand on the cold concrete. Look at the view. Log the visit.
Then see if you don't immediately start looking for the next one.
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