GPS Major Error Sources Orbital errors and Selective Availability(SA) o nominal error for the broadcast ephemeris: 1-5 m on average a precise(post-mission orbits are good up to 5-10 cm and better; available with 24-hour delay a Selective Availability: not observed on the orbit a first-order orbital errors are removed by differencing technique wv Principles of the Global Positioning System Basic atmospheric structure 30° Troposphere is where the temperature stops decreasing in the atmosphere. (10 km altitude) stratosphere Gv Principles of the Global Positioning System 2005-4-1 84 Principles of the Global Positioning System 2005-4-1 7 GPS Major Error Sources Orbital errors and Selective Availability (SA) ‰ nominal error for the broadcast ephemeris: 1-5 m on average ‰ precise (post-mission) orbits are good up to 5-10 cm and better; available with 24-hour delay ‰ Selective Availability: not observed on the orbit ‰ first-order orbital errors are removed by differencing technique Principles of the Global Positioning System 2005-4-1 8 Basic atmospheric structure Troposphere is where the temperature stops decreasing in the atmosphere. (~10 km altitude)