5
Oct
2017
0

Britain’s top trig-bagger adds FBMs to his haul

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.

Rob at Windsor Castle’s FBM

Efficient baggers also visit the passive stations* (blocks, bolts, rivets, Berntsens etc) and active stations at the same time as pillars and FBMs. I didn’t get round to these until I bought a GPS in 2009 (as passives are often buried and can be hard to find without GPS) and this has been my main trigging focus in the last few years, especially since finishing the pillars. I have about 40 of these left – the hardest to reach is probably Sule Skerry, a bolt situated beside a lighthouse on a tiny, hard to land on island off the North coast of Scotland.

NPFBs is a good list to pursue – I have over 6,000 of these with around another 2,000 surviving NPFBs still to visit. Householders are quite often interested to learn about these strange bits of metalwork attached to their properties. However, I’ve not added many recently. As it happens, I’m currently visiting a fair few “ordinary” benchmarks (cut marks, rivets, pivots etc) as I have a fractured thumb which limits me to public transport or walking from home – and (as they say about rats) wherever you go, you’re never far from a benchmark!  I’ve no plans to try and visit all quarter million of them though.

Normally, my main ongoing focus is hill-bagging. Even so, I often come across benchmarks and sometimes non-pillar trigs (usually surface blocks) in the process.

If you’d like to follow in Rob’s footsteps and bag FBMs, take a look on the TrigpointingUk website: http://trigpointing.uk/trigs/view-trigs.php?q=2077404

*If you hadn’t hear of passive stations before, these were our geodetic GPS-compatible network, before OS Net. Just like ‘traditional’ surveyors with theodolites required trig pillars to act as control points with accurate eastings and northings, GPS surveyors needed control points with accurate ETRS89 coordinates (the GPS-compatible coordinate system used across Europe). The passive stations all had accurate ETRS89 coordinates and are also in places suitable for GPS – easy (i.e. 2-wheel drive) access 24 hours a day with an open view of sky.  So, no need to hike up a hill or climb a church tower with your GPS kit to access a survey control point!

The passives have now been superseded by OS Net and our surveyors no longer use them. However, like trigs, they remain valid survey points and surveyors are free to occupy them if they wish.

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