The Global Positioning System (GPS) can provide centimetre-level positioning accuracy in “open-sky” environments. However, GPS coordinates become unavailable in difficult urban and rural environments because the GPS signals may be partly or completely blocked by trees and buildings. Applications such as underground asset mapping or locating unexploded ordnances require a “seamless” precise navigation capability even under trees and across all terrain. In the case of buried utilities (pipes, cables, conduits, etc.), the need to know “what is buried where” is well recognised for both maintenance and planning purposes. Lack of accurate geolocation knowledge can result in unexpected costs and serious property damage. In order to ultimately produce a 3D model of buried infrastructure, it is necessary to develop “non-contact” underground mapping systems and associated high accuracy urban navigation.

In an attempt to address the demands for high accuracy navigation to support man-portable, ground-penetrating imaging systems, this paper describes an integrated system based on the “triple-integration” of GPS, inertial navigation systems (INS) and the recently developed RF- based navigation system “Locata”. Although traditional GPS/INS integrated systems can bridge relatively short GPS gaps, its capability heavily dependent on the accuracy (and ultimately the cost) of the INS. The Locata system broadcasts strong time-synchronised ranging signals over an area where GPS satellite geometry is poor or the signal availability is limited. This paper describes preliminary results from the triple-integration of GPS/INS/Locata, and discusses its suitability for the navigation demands of underground utility mapping systems.