Using Wilkins' knowledge that shortwave signals bounced off aircraft, a BBC transmitter to light up the sky as in Appleton's experiment, and Watt's RDF technique to measure angles, a complete radar could be built. However, while such a system could determine the angle to a target, it could not determine its range and thereby produce a single location in space. To locate the target, two such measurements would need to be made and the location calculated using triangulation,[16] a time-consuming process that would be subject to any inaccuracies in either measurement or differences in calibration between the two stations.