Re: Don't mess with evolution!
The Pokestops (seriously) were all created / discovered by Ingress players that had to be at the site and take a picture. This process stopped around a year ago so no new pokestops or portals unless you have a deal with Niantic.
Altitude does not matter as all portals are assumed to be at ground level, as is the player. You can spin pokestops and capture portals etc in a helicopter at 1000 ft if you really want to, I have seen it done.
You also get an account ban if they even suspect you are faking the gps location. They are very good at catching people doing this.