Abstract: The disclosure involves a method for guiding a machine within an area. Such method includes the steps of triggering an acoustic locating signal from a stationary "beacon-type" base module to a receiver on the machine. The method is applicable for one-beacon, two-receiver and two-beacon, one-receiver applications. A related apparatus also includes a device for emitting a trigger signal and a device for determining the time elapsed between transmission and reception of the locating signal. An operating principle involves computing the module-to-machine distance by determining the "time of flight" of such signal. The machine is steered along a path, the locus of which is defined by an equation.

Abstract: An apparatus for determining an area of a surface which is traversed and treated by an object during a unit of time is configured for use with a moveable object that has a first axis of a known length. The object is capable of movement along a second axis and the first and second axes define an angle between them which is other than 0.degree.. A signalling means includes a sensor which may be mounted in a motion-sensing relationship to the object for providing a motion signal when the object moves a distance along the second axis. The motion signal has a predetermined relationship to that distance. A timing means repetitively provides a plurality of timing signals, each sequential pair of which defines an interval of time of known duration. A computing means is coupled to the timing means and to the signalling means for receiving at least one sequential pair of timing signals and at least one motion signal.