A process in which a mobile station is directed, or directs itself, toward an electromagnetic, thermal, sonic, or other source of energy, whether primary or reflected, or follows a vector force field or a gradient of a scalar force field. 2. In radio direction-finding, the locating of a moving signal source by a moving direction-finding station that has a mobile advantage. 3. The act of approaching a source of electromagnetic radiation in which the approaching vehicle is guided by a receiver with a directional antenna. 4. Seeking, finding, intercepting, and engaging an object, i.e., a target (fixed or mobile) that may contain a signal source.