Nah, SSA is the Scratch Scoring Average - ie what a 1000 rated player should be shooting.
It's not completely relative to the ratings of the players that are on the course that day, though that does weigh in the calculation.
It is completely relative to the ratings of the players that are on the course that day. The SSA is entirely calculated from the way players with established ratings shoot that day, it doesn't take the course or other events into account at all.