"Scanning" the River

I took a dog for a walk today and we went on our usual route that runs beside the river Isis, what we in Oxford call the Thames. When we arrived I got a bit of a shock. A section of the towpath had been closed by the police, or at least I assume they were police because of their uniform; but they could have been somebody else in disguise. One of them was standing by a lock where I usually join the Thames Path and he said: "Could you go that way instead please, sir." He pointed to the old stone bridge. "We're just doing some scanning." He didn't explain what he meant by scanning. I crossed over the bridge and saw a big police warning sign announcing that the path was closed; another identical sign had been set up on the path about a hundred yards away downstream. A group of three or four other men in police uniforms were operating some kind of machine raised on a tripod. There is a patch of woodland right beside the lock and a muddy track runs through it; therefore I was able to double back to where the cordon was, hidden by the trees. It was there that I took this series of photographs.

The edge of the police cordon.

Policemen, or what looks like them, on an operation beside the river Isis (Thames) in Oxford.

The machine they were using for what they called "scanning". Do any readers recognize this? If so please let me know in the comments.

While I was walking through the woods close to where the scanner was I came across several dead animals, two rats and a squirrel. It is unusual to see that many corpses together in such a small forest. They did not look like recent deaths though, so I'm not saying whatever the scanning machine was killed them. If so I would have fled the location out of fear for my own health and that of the dog. There were also a large number of animal bones. The dog picked up a section of jawbone from what looked like a deer and, as usual, I had a bit of trouble persuading him to put it down. There was nothing else out of the ordinary at the location. I'm not sure what was going on; except a few months ago the police, definitely the real police this time, shut that same stretch of the Thames Path to perform a reconstruction while investigating an accident in which a pedestrian was killed by a speeding cyclist, see: https://www.oxfordmail.co.uk/news/23679085.oxford-cyclist-accused-thames-towpath-death-court/. I don't know if there's a connection. There has been nothing in the news about today's goings on. I'll be walking the same route tomorrow at about the same time of day so if anything else is untoward I will report on it.