Development and Pseudolite Applications in Positioning and Navigation

Although the Global navigation satellite systems (GNSS) introduced a revolutionary change in the areas of positioning and navigation, it is well known that the precision, reliability, availability and integrity of the results obtained by this technology, heavily depend on the number and geometric distribution of the satellites being tracked. This is especially problem in areas with limited sky visibility, such as urban canyons, valleys, deep open-pit mines, larges construction sites. Furthermore, indoors, or underground, such as factory halls, inside buildings, tunnels, positioning is totally disabled due to unavailability of satellite signals. These limitations can be overcome by including additional ranging signals transmitted from pseudolites (the term derived from the pseudo-satellite), ground-based generators and transmitters of GPS-like signals, for use in the local area. Pseudolites can be used to augment the GNSS satellite constellation in case of inadequate satellites coverage and to improve the geometry, and as an independent measurement system that can completely replace the GNSS, such as indoors, underground or on the surface of other planets. While this may seem like a new measurement technology, the concept of ground-based transmitters can be tracked back to the early development of GPS, when the pseudolites been designed to test the GPS user equipment. Since than, seeing that the pseudolites can be successfully used for other purposes, researches teams around the world continuously improve and develop new pseudolite concepts and hardware, trying to adapt them to the requirements of certain applications. This paper presents the theoretical basis, advantages and disadvantages, technology development of pseudolites, further research, and new construction, and application of pseudolites in some areas of positioning and navigation.