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Mystery Item


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Any body know what this is?

 

It's about 6", a plate screwed to the decking around a pond used for pond dipping. The site manager has no idea, various 'officers' have looked at it and not seen anything like it.

 

(Found on the way to a cache - so sort of cache related)

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My guess is something for visual alignment, but that is just a guess.

 

Has any form of race been help in the pond? Model boats for example.

 

No, it's in the middle of an RSPB/National Trust wildlife reserve, quite close to Sizewell Nuclear thingy.

 

Clearly not 'aligned' e.g. not north/south etc, as it is too neatly aligned with the decking. But you get the feeling it is for placing something like a surveying post. But we can't see any other point anywhere in the area. I would expect to have other similar points around, or some recognised place for placing a theodolite.

 

The people that work at the site are sure it's the only one there.

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I think it is a TBM (Temporary Bench Mark), as Nige says used in surveying but not part of the official network. You will often find TBMs in the form of small studs in pavements which will have been used by surveyors to transfer a level from an OS Benchmark to a building project or maybe also to monitor ground movement.

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No, it's in the middle of an RSPB/National Trust wildlife reserve, quite close to Sizewell Nuclear thingy.

So it's obvious then. It will be used for photo finishes of the radioactive bird racing. They can go rather fast you know. :laughing::laughing:

 

it's used in surveying

It may well be correct, but is it as fun as the bird explanation? I think not! :blink:

Edited by alistair_uk
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Something to do with Secchi discs?

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Right sort of context, supposed to be repeated at the same site so maybe marks the spot to do it...?

Overall, I prefer the radioactive bird theory - maybe if a test one crashed into the pond at high speed it made the water really turbid and, and, what was the question again?

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Well I'm enjoying the answers so far.

 

It looks remarkably like a Secchi disk, but is screwed to the platform that you stand on to do pond dipping, so would never be underwater.

 

The position is wrong for the photo rectifying thing, unless it was a helicopter shot. The decking goes up against a high bank, so isn't really visible from anywhere other than directly above or standing on the decking, and any picture that had the disk in would just have a close up of the bank.

 

I'm pretty convinced that it is a marker to stand a pole on to do surveying. The area is being eaten away at around 1 metre a year so I'm sure they must be doing all sorts of stability checks.

 

But radio active duck racing.... I can feel a whole new sport coming. Might just save Grandstand.

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I can tell you what it is. we use those at uni. Its a Field Archery target. If you look around the area (within 140ft) you would find 3 small wooden posts (pegs) one yellow, one red, one black.

 

I wouldn't want to be nearby when they are doing that Archery as it appears to be flat on the floor.

I think the radioactive duck would want to be out of the way too :(

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I don't think it'll be a field archery target. It's right next to a pond, so half the arrows would go in the water?

 

From the photo, it's flat on the ground, screwed to the planks of the jetty / landing stage. It's bout 4-6 inches square.

 

If the pond is dipped to check the level, then that level needs to be referred to some vertical datum (like the edge of the jetty). This level needs referencing back to Ordnance Datum, which means that someone needs to level it. When they levelled it, they hammered in a nail to use as a known reference point (or Temporary Bench Mark TBM) in future. Because it's very difficult to find a small nail, they've put an easy to see disc on it.

 

So my suggestion is that it's a marker for a survey nail.

 

I like the idea of it being used to ortho rectify (technical word for "stretch to the right shape") aerial photos. That's quite possible aswell, although I thought that aerial photographers generally used mapped features to do this.

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