A method of calculating in near-real-time two possible angles of elevation of a projectile and associated times of flight so that the projectile can be made to act at a desired point The angle of elevation of the launching direction of the projectile and the time of flight are calculated in a process which is divided into two main parts, a calculation part which discretely timed calculates positions and associated points of time along a trajectory, and a logic part which sets a first direction of elevation, monitors the calculation of projectile positions and time of flight and interrupts the calculation at specified points to determine a solution, Then the logic part sets a second direction of elevation until two solutions have been found.