7.3: Absolute and relative satellite navigation

7.3.1 Description of the navigation satellite system setup

As in the previous section, only the basic measurement principles required for a general understanding of absolute and relative navigation via navigation satellites will be described here. For more detailed information, readers are referred to the literature on the subject, such as Ackroyd & Lorimer (1990), Scott et al. (1995), Kaplan (1996), Dye & Baylin (1997), Kayton & Fried (1997).

Satellite navigation systems are radio navigation systems based on signals transmitted by a set of satellites orbiting the Earth. They provide navigation information to the user through measurement of range and range-rate between a user receiver and a subset of these navigation satellites. Satellite navigation systems are generally composed of three segments:

1. a space segment, including the navigation satellites as the active partners of the user in obtaining the navigation information;

2. a ground segment, controlling the orbital parameters, the accuracy of onboard time and the accuracy of the navigation messages broadcast by the navigation satellites;

3. a user segment, consisting of the navigation receivers, the locations of which are to be determined. More than one receiver may be used in cooperation to improve relative navigation accuracy between those receivers (see DGPS and RGPS).

At the time of writing, two major navigation satellite systems are deployed:

• the Global Positioning System (GPS), developed and operated by the United States of America;

• the Global Orbiting Navigation Satellite System (GLONASS), developed and operated by Russia.

Because of the importance satellite...