Measuring direction of object (or angle of signal origin)
If you're locating an object through auditory means, you'll need at least two receptive transducers - measure the difference in sound arrival time. Three are much better; you won't have to rotate the transducers for a second "ping" arrival.

If you're locating through radio means, you'll need a rotatable directional antenna... or three omnidirectional radio antennae. If one, you'll rotate it until signal strength is strongest. If three, you'll select the strongest and extrapolate direction from the relative strengths received by the other two.