Why do We study orbit? The applications of gPs depend substantially on knowing the satellite orbits 1. For single receiver positioning, an orbital error is highly correlated with the positional error In relative positioning, relative orbital errors are considered to be approximately equal to relative baseline errors 電 Principles of the Global Positioning System 2005-3-11(5 Orbit Information and SA Technology How to obtain orbital information: o either transmitted by the satellite as part of the broadcast message or o can be obtained(typically some days after the observation) from several sources Principles of the Global Positioning System 20053-11(63 Principles of the Global Positioning System 2005-3-11 5 Why do We Study Orbit? The applications of GPS depend substantially on knowing the satellite orbits. 1. For single receiver positioning, an orbital error is highly correlated with the positional error. 2. In relative positioning, relative orbital errors are considered to be approximately equal to relative baseline errors. Principles of the Global Positioning System 2005-3-11 6 Orbit Information and SA Technology How to obtain Orbital Information: ‹ either transmitted by the satellite as part of the broadcast message, or ‹ can be obtained (typically some days after the observation) from several sources