A friends parking lot is regularly full of cat droppings left by numerous felines in the area. As you can imagine, it's quite a nuisance; he regularly needs to wash it to avoid
swimming walking in the droppings.
How could he keep the cats out?
There are multiple parking lots in the same underground parking, but droppings are nearly exclusively in his lot. If possible, the solution should avoid just moving the problem to a new victim, but more importantly shouldn't be a nuisance to the other users of the parking.
The cats are presumably strays.
The crimes are committed at night, and he isn't ready to stay up!