A duct mapping tool comprises a sonde for transmitting a locate signal detectable above the ground and locomotion means for providing movement through the underground duct. A user above the ground detects the transmitted location signal using a signal receiver, and maps the location of the underground duct. In one embodiment, a GPS receiver generates location data at locations associated with the received location signal. The GPS generated location data may be used in conjunction with appropriate mapping software to generate street level maps of underground ducts. Locomotion can be provided in a variety of ways, such as a flexible rod attached to the duct mapping tool and operated by a technician, air motors, or electric motors. Movement control signals may be sent to the underground duct mapping tool via a remote device controlled by a technician.