Is there a way to determine exactly where the security van is going to be GTA V

Is there an in game without the use cheats to determine where the next security van is going to be? Do they all follow the same routes at a set time or spawn at a set location first? Or even better is there a mod out there that can mark them on the map?

According to the GTA Wiki, you can't because they spawn randomly on the map:

• Will appear as part of a Random Event in which the player can steal money being transported by a Stockade. The player can either attack the guards accompanying the car and steal the money directly from them, or blow off the back doors and steal the money from the Stockade itself. The player can then take the Stockade for themselves.
• It will sometimes spawn randomly in traffic, outside of side missions.

http://gta.wikia.com/wiki/Securicar#Grand_Theft_Auto_V_2

In GTA Online:

Will appear when unlocked as a target for robbery.

http://gta.wikia.com/wiki/Securicar#Grand_Theft_Auto_Online_2