Question L4-C2

The question is about the possible obstacle sensor used by a robot in a particular situation, given here by the type of robot - a miniature drone - and the environment - a corridor with a lot of visual features on the walls. On the right an illustration of the relative angles to the various features, and a picture of the test room with a lot of red features on the walls. The question is: "In a publication you see the picture on the right, about a miniature flying system measuring the distance from obstacles (Fig. a, on the left), and in an environment
specifically designed for this experiment (Fig. b, on the right). Based on the image, you can guess that the detection and measurement of distance to the various distinct obstacles is done by:". Three possibilities are proposed:

Answer A: "A set of 45 ultrasonic sensors, one each 4 degrees, to cover the forward motion"
This answer is wrong, as 45 ultrasonic sensors are too large for this task. An ultrasonic sensor needs to generate a sound wave and has therefore a size that is much larger than what we are describing here.
In the explanation of the student we would like to see that they understand that an ultrasound sensor is bulky and 45 cannot be mounted on a miniature drone.

Answer B: "Vision with wide angle"
This answer is correct, as the environment has a lot of visual features and using optical flow, one can perform this obstacle avoidance.
In the explanation of the student we would like to see that they understand that the rich visual features are a very good condition for a vision sensor. Here it could be nice if they mention optical flow as a technique.

Answer C: "One ultrasound sensor toward the front with a large angle of detection"
This answer is wrong, as one single ultrasonic sensor cannot ensure “measurement of distance to the various distinct obstacles”. It can made one single measurement.
In the explanation of the student we would like to see that they understand that an ultrasound sensor cannot make distinct measurements to several objects, despite it can have a large angle of measurement.