The current invention relates to methods and systems for evaluating a filling state of a load bearing means by means of a monitoring system comprising a sensing module; said load bearing means adapted for being carried by a transport unit; said load bearing means comprising a loading space; said sensing module situated in proximity to said load bearing means and outside of said loading space; said sensing module comprising an emitter, a receiver, an evaluator and a memory comprising calibration data; said sensing module configured for carrying out a plurality of steps; wherein a spacing S between said emitter and said receiver does not exceed 200 mm; and wherein a maximum dimension M of said load bearing means is not smaller than 4 m.