What the heck is this?

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Brian
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#1
I was walking by the River Thames in London recently and spotted this bolted to the embankment wall near Blackfriars Bridge.
It's clearly labelled "Leica" so it's obviously a piece of optical equipment, and a search for "GMP104" identifies it as a "Monitoring Mini Prism," but does anyone know what it's for?

Leica Bracket.jpg
 
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Dominic
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#2
It says they are used for Monitoring displacement and deformation. So I would hazard a guess that they are monitoring the embankments for movement.
 
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Gary
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#3
They are there to watch for movement in the Embankment while they dig the new super sewer from Acton in West London to Abbey Mills in East London, a distance of about 16 miles mostly under the Thames.
 
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Dave
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#4
They are all over the place, somewhere there will be a total station that will measure the precise location of the markers within its area. These positions are then compared against previous readings to determine if any movement has taken place.

It is quite common around large civil engineering projects, many in London are related to cross-rail to ensure that the tunneling under the city is not causing any undue building movements.


Interesting factoid - While the basement car park under the housed of parliament was being excavated, big Ben, or rather Elizabeth Tower, was being monitored to check for movements. At some period of the excavations all works was stopped as it was noted that the tower had leaned over which cause a bit of panic. A more intensive period of monitoring took place while the works were stopped and it turned out that the tower leaned over and returned back to its original position twice a day, coinciding with the high tide. It turned out that the movement was entirely down to the pressure of the water acting against the embankment and had nothing to do with the excavations at all.
 
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Brian G
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Brian
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#8
Ah yes! And we complain about the cost of cameras!

Thanks all for the replies.
I thought it was some kind of monitoring device related to the construction work being carried out along the Thames in relation to the new "Super Sewer"
Presumably the "active" part is on the opposite side of the river, where there is a large construction site.
I must keep a lookout for others.

They never had this sort of technology when Joseph Bazalgette built the original embankments in the 1860's!
 
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#12
A more intensive period of monitoring took place while the works were stopped and it turned out that the tower leaned over and returned back to its original position twice a day, coinciding with the high tide. It turned out that the movement was entirely down to the pressure of the water acting against the embankment and had nothing to do with the excavations at all.
The BBC had a different take on the story which you can read here: https://www.bbc.co.uk/news/uk-england-15243118
 
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wayne clarke
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#14
Some of the early burglar alarms used something similar, you had something like a cycle reflector and opposite ar IR beam, anything that broke the reflection would trigger the alarm. (a bit like the old spy films where they'd make the beams show up to climb over them)
In this case it's as mentioned already measuring distance/movement .
 
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