Answer 6—Knowing the angle whose vertex is at the beacon and the spacing of the two sensors on the robot, you can describe a locus of points on which the beacon must lie in relation to the baseline that joins the two sensors.

In two dimensions, this locus is a circle (actually one of two circles). If the angle is 90°, the baseline joining the two sensors is a diameter of the circles. (The two circles are coincident in this case.) Otherwise, the baseline is a chord of the circle, which is reflected about this line. Obviously, this is not yet enough information to pinpoint the location of the beacon with respect to the robot (or vice versa). A third (or fourth) sensor is required to disambiguate the possible solutions.

Contributor: David Tweed