You see a map of unique jumps in GTA San Andreas. As you progress through the game you can run up to 70 unique stunt. All jumps are marked on the map of 3 islands of San Andreas'a. Unique jumps can be performed on any kind of transport.
To perform a stunt in GTA San Andreas thing to pick up a fast car or motorcycle and want to be dispersed. On the tractor or the bike a unique jump do not happen-you simply will not be dispersed to the required speed.
Download: map of unique jumps in GTA San Andreas