an ultrasonic ranging and data telemetry system determines a surveyor &# 39 ; s position and automatically links it with other simultaneously taken survey data . an ultrasonic and radio frequency transmitter are carried by the surveyor in a backpack . the surveyor &# 39 ; s position is determined by calculations that use the measured transmission times of an airborne ultrasonic pulse transmitted from the backpack to two or more prepositioned ultrasonic transceivers . once a second , rf communications are used both to synchronize the ultrasonic pulse transmission - time measurements and to transmit other simultaneously taken survey data . the rf communications are interpreted by a portable receiver and microcomputer which are brought to the property site . a video display attached to the computer provides real - time visual monitoring of the survey progress and site coverage .