Some of you may remember Rob Woodall, we shared his story in 2016 as he completed a 13-year mission to bag 6,190 trig pillars across Great Britain. Not content with that, Rob’s now added all 201 fundamental benchmarks (FBM – see photo below) to his haul. Rob fills us in on his challenge and talks about other OS survey marks he likes to bag along the way…
My first FBM was Wolsingham in lovely Weardale, in 2004. A group of us get together once a year, and that year the gathering was hosted by a couple who live in Wolsingham and they put together an itinerary which included trig pillars (my main interest at the time) and also mysterious things such as non-pillar flush brackets (NPFBs, which are FBs on structures other than pillars, such as houses, churches, bridges etc) – and the local fundamental benchmark. So I started ticking off NPFBs and FBMs too.
It’s taken 13 and a half years to bag 201 FBMs (including all but 6 of the destroyed ones – which I’ll get round to eventually) – coincidentally about the same time it took to bag 6,190 trig pillars – which is not great productivity. However, the last two were Patrington (which we all thought was destroyed until it turned up in 2016 when the householder took out a big laurel tree in their garden) – and Windsor Castle which we all assumed was out of bounds. Eventually a friend sent off a letter to the Royal Collection Trust to see if we could visit the FBM, and the answer was yes! – provided HRH was away at the time. So with no particular plan, I ended up finishing the list this year.
When we decided to celebrate the 80th anniversary of the trig pillar last year, we had no idea how strongly so many of you felt about the (mostly) concrete pillars dotted around Britain. We’ve had over 1,200 Instagram posts, uncovered dozens of trig baggers, seen Rob Woodall complete his 13-year mission to bag all 6,190 and had hundreds of people, magazines and websites share stories throughout the year.
With 18 April fast-approaching, #TrigPillar80 is drawing to a close, and #TrigPillar81 doesn’t have quite the same ring to it. So, huge thanks to everyone who took part and keep sharing your trig pillar love with us. Here are 7 fantastic things about trig pillars in case you missed all of the celebrations this year:
We have genuinely loved seeing all of the fantastic trig pillar photos that you’ve been sharing with us as we celebrate the 80th year of the trig. Across Twitter and Instagram you’ve sent in an amazing 1,656 entries of trigs across Britain. We highly recommend going and checking some of the entries out.
Our final winners have been picked and all of our T-shirts have now been given away. Check out the final winners below, and see all of the winners in our blog post.
Hands up if you’re looking for some free family activities over the summer holidays? We thought so…how about a spot of trig bagging to get the family outside? This year we’ve been celebrating the 80th anniversary of the trig pillar, those concrete pillars that are often found at the top of hills and create a handy photo opportunity.
Once a key part of our surveying network, and since superseded by GNSS, they stand tall and mark the summit of many a walk. With around 6,000 still standing around Britain you stand a fair chance of spotting one when you’re out exploring, and you can spot them on your map as the small blue triangle with a dot in the centre.
We’ve been thrilled at your response to our #TrigPillar80 celebrations over the last month and are loving looking at all of the photos you’ve been sharing with us on Twitter and Instagram. We’ve also heard from some of you who are on a trig bagging challenge. Here, Gerry McGarry tells us more about his geocaching and trig adventures…
Over the last couple of years, I have visited geocaches that have been hidden close to trig pillars. This led me to investigate trig pillars and I discovered some interesting sites on the internet, especially trigpointingUK. I then discovered that there is more to old Ordnance Survey markers than the pillars and encountered bolts, rivets and other interesting OS markers. Close to the end of 2015, I noticed that I had found 85 pillars during that year and I upped my game and bagged exactly 100 pillars during 2015.
Yesterday marked 80 years since the trig pillar was first used in the retriangulation of Great Britain on 18 April 1936. On that day, a group of surveyors gathered around a white concrete pillar in a field in Cold Ashby and began the retriangulation of Great Britain.
We’re celebrating by sharing the story of the humble trig pillar, still much loved by walkers today, and giving you the chance to join our celebrations with The Trig Pillar Trail Challenge. But what is the background to the trig pillar?
Amidst the joy of our Christmas celebrations this year, staff at Ordnance Survey will be remembering the contribution made to the national mapping agency by Brigadier Martin Hotine CMG CBE RE.
Brigadier Hotine served in the Royal Engineers for many years and saw active service in both the First and Second World Wars. However, it was during 1934–1939 when he worked at Ordnance Survey heading up the catchily-titled ‘Trigonometrical and Levelling division’ when he made the contribution which we’ll be remembering.
Hotine was the person responsible for the design, planning and implementation of the re-triangulation of Great Britain on which Ordnance Survey maps are still based. During this inter-war period, he designed the iconic and much-loved Trig Pillar which is still found now on many hilltops and in the countryside across Great Britain.
On a clear, crisp spring morning in 1936, a group of men gathered around a strange, pale obelisk in the middle of an unremarkable field in Cold Ashby, Northamptonshire. Those men were there to begin the greatest undertaking Ordnance Survey had attempted since the early 19th century.
That shining white monolith would now be instantly recognised by any walker, hiker or geography pupil. It was of course a Trig Pillar, and today, 18 April, marks 75 years since the day when they were first used in anger at the beginning of the Retriangulation of Great Britain.
Trig Pillars now evoke the kind of sentimentalism of something quintessentially British (although there are equivalents in other countries), but at the time they were part of a state-of-the art network built to literally re-write the map of Britain. The Retriangulation was an enormous task and lasted up until 1962 (with a break for World War II), the impact of which we still live with today.
Triangulation is basically a mathematical process that makes accurate map making possible. It works by determining the location of a point by measuring angles to it from known points at either end of a fixed baseline and in this case, those known points were the 6,500 Trig Pillars erected across the country. In practice, a theodolite would have been secured to the top mounting plate and made level. It would then be directly over the brass bolt underneath the pillar. Angles were then measured from the pillar to other surrounding points. For the highest accuracy primary points in the Retriangulation, many rounds of angles would have been measured with the observations taking several hours.
But why was the Retriangulation needed?