Pseudolite Applications in Positioning and Navigation: Progress and Problems

Global navigation satellite systems have been revolutionising surveying, geodesy, navigation and other position/location sensitive disciplines. However, there are two intrinsic shortcomings in such satellite-based positioning systems: signal attenuation and dependence on the geometric distribution of the satellites. Consequently, the system performance can decrease significantly under some harsh observing conditions. To tackle this problem, some new concepts of positioning with the use of pseudo-satellites have been developed and tested. Pseudo-satellites, also called pseudolites, are ground-based transmitters that can be easily installed wherever they are needed. They therefore offer great flexibility in positioning and navigation applications. Although some initial experimental results are encouraging, there are still some challenging issues that need to be addressed. This paper reviews the historical pseudolite hardware developments and recent progress in pseudolite-based positioning, and discusses the current technical issues.