Zothecula writes "We've seen it in numerous TV shows and movies – the witness to a crime looks through a book of mug shots, then works with a police sketch artist to come up with a likeness of the nasty person they saw. After looking through hundreds of mug shots, however, it's possible that the tired-brained witness could look right at a photo of the guilty party and not recognize them. It's also possible that there is a mug shot of the criminal on a database somewhere out there, but that this particular witness will never see it. A computer system being pioneered at Michigan State University, however, could be the solution to such problems – it automatically matches faces in police sketches to mug shots."
I've never been canoeing before, but I imagine there must be just a few
simple heuristics you have to remember...
Yes, don't fall out, and don't hit rocks.