Question L6-C3

The question is about the sensors that can be used for the localisation of a robot working in empty feature-free rooms. On the right there is an illustration of room, totally white with nothing on the wall, the ceiling or the ground. All is white. The question is: "You have to design the perception part of a navigation system for a robot making fast inspections of empty office buildings, with large uniform rooms. Which of the statements below are correct (multiple correct answers possible)?". Three statements are proposed:

Statement A. is "Active beacons using projected patterns on the ceiling would be a very interesting solution, even if a bit costly.". This statement is correct, as active beacons would project well-known features on the feature-less walls and ceiling, making localisation easier.
In the explanation of the student we would like to see that they understand that this solution, based on generation of markers, is less dependent from the features present in the environment.

Statement B. is "Ultrasound sensors would allow to precisely and quickly measure distance to the walls.". This statement is wrong, ultrasound have large measurement cones are cannot be very precise in various situations. Moreover in such empty environements, ultrasound can bounce and generate wrong measurement. Finally they are slow, not fast as expected from this application.
In the explanation of the student we would like to see that they understand that these sensors are not precise nor fast.

Statement C. is "Stereo cameras would allow a precise passive measurement of the distances.". This answer is wrong: here there are not many visual features on which one can make matching between the two images.
In the explanation of the student we would like to see that they understand that stereo cameras rely on visual features, not present here.

