Positioning using a transponder

If you think of a transponder as a landmark, the transmission of an interrogation signal from an object whose position you would like to identify (for example, observation equipment to observe underwater) allows you to determine the distance between them. In reality, the position can be identified by installing transponders at three locations and measuring the distance to each transponder.

A circle can be drawn if the distance to one location is known. In other words, if you know that the object is located somewhere on this circle. If the distance to another location is known, then another circle can be drawn, and you know that the object is located at one of the two intersections of the circles. Furthermore, if the distance to another location is known, there will be one intersection of the three circles, allowing the identification of the position of the object.