Summary of the equations governing the default controller (i.e boxes 5–7 in Fig 3).

Line 2: The speed of the bat Vbat is set as a function F of the distance to the nearest obstacle dmin (using the curve depicted in Fig 1a). Next (lines 3–14), the speed Vbat is used to set the rotations of the bat in azimuth (Δϕ) and elevation (Δθ). The sign of the azimuth rotation depends on the relative strength of the echoes at the left (gl) and the right ear (gr) as given by Eq (3). The sign of the elevation rotation depends on whether the ear with the weakest echo is pointing up or down.