litterbox accidents

Question
I have a 12 year old neutered male cat, who stays indoors.  He sometimes pees on the floor outside the litterbox; sometimes, about a foot away (not always in the same spot). I thoroughly wash the area and apply a peroxide-baking soda-detergent solution to kill the odor.  He was seen by the vet and he was declared healthy, no UTI (though he has had them in the past).  He will be good for a while, then suddenly he will pee on the floor.  There has been no changes in the household to cause this behavioral problem.  However, there are a lot of stray cats in my neighborhood and occasionally stroll through my yard, and I have seen the male ones spray.  My cat sees them and becomes upset. He likes to sit at the screened basement window, which is at ground level.  The litterbox is also in the basement.  Several times, I have heard cats snarling and spitting at each other at the window (mine and the stray).  Now, my question is: Could this litterbox problem be related my cat getting upset about seeing another cat in "his" yard and maybe getting too close to the window?  I'm aware that cats are territorial.  And if so, do you have any suggestions to prevent this from happening?  I'm sorry for being so long-winded here.  Thanks for any help you can give me.

Answer
I'm glad you had him checked by your vet already, that is always my first recommendation. The next result is, yes, it is more than likey that it's because of the stray cats. The unfortunate thing is, it doesn't matter how close they are to the house, your cat can smell them from a large distance away. It definitely doesn't help the situation that they come so close to the house.

I think what I would try is somehow blocking the view from the most detramental location, which seems to be in the basement. I would also try moving the litter box as that is now his territory and only sees the strays as coming into his territory. You can also use pheromone sprays to help calm your cat down. If you're not sure what they are, they're synthetic hormones that naturally come fromt the scent of the mother that give the essence/aura of calming or neutralizing.

Let me know how things go and if you think of any more questions.