I have found that human pee is one of the best deterents for cats, just sprinkle it around in the spot were it craps. Using a bucket will keep your modesty intact. Without wanting to sound pervy I found that the wife's worked better than mine.
in my front garden i built a raised bed,and the cats would love doing the bizz in it everynight...i did put cocktail sticks in,bloody hell look funny and it did stop em for awhile.i bought a real christmas tree this year and when the wife tryed removing the decs n lights most of the needles came off all over the floor so swept them up ,got about a carrier bag full,and threw em on the raised bed,problem solved it seems the cats hate getting those lil needles stuck between they toes haha.
i live close to a pine forest so going to collect all the fallen pine needles from em and top up now and again .