Welcome to the Forum. Hopefully some of the ideas will be useful to you. And yes photos will be gratefully appreciated.
By any chance, this spot that he has picked to urinate on, could another animal in the past have peed there, and for some reason that spot is bothering him and he has decided on marking it. If so it could take several good soakings at least of a good enzyme cleaner as mentioned before to hopefully put an end to him using that spot.