9.1 INTRODUCTION

Before commencing this chapter, the reader should have studied Chapter 8 and acquired a knowledge of geoid models, ellipsoids, transformations and heights, i.e. Sections 8.1 to 8.8. The subject of satellite positioning is changing fast. Throughout this chapter a number of websites are referred to for further information and data. The websites are mostly government or academic and are considered to be likely to be maintained during the life of this edition of this book, although of course that cannot be guaranteed.

The concept of satellite position fixing commenced with the launch of the first Sputnik satellite by the USSR in October 1957. This was rapidly followed by the development of the Navy Navigation Satellite System (NNSS) by the US Navy. This system, commonly referred to as the Transit system, was created to provide a worldwide navigation capability for the US Polaris submarine fleet. The Transit system was made available for civilian use in 1967 but ceased operation in 1996. However, as the determination of position required very long observation periods and relative positions determined over short distances were of low accuracy, its application was limited to geodetic and low dynamic navigation uses.

In 1973, the US Department of Defense (DoD) commenced the development of NAVSTAR (Navigation System with Time and Ranging) Global Positioning System (GPS), and the first satellites were launched in 1978.

The system is funded and controlled by the DoD but is partially available for civilian and foreign users. The accuracies that may be...