Abstract--This paper proposes an interval based method for the validation of reliable and robust navigation rules for mobile robots. The main idea is to show that for all feasible perturbations, there exists a safe subset of the state space such that the system cannot escape. The methodology is illustrated on the line following problem of a sailboat and then validated on an actual experiment where an actual sailboat robot, named Vaimos, sails autonomously from Brest to Douarnenez (more than 100 km).