Processing methods The clock and local oscillator phase variations are the biggest deviations in the model of GPS phase and range data These terms can be explicitly handled by estimation of clock variations(but if done brut-force in least squares with sequential LSQ or a Kalman filter an be attacked is a very large estimation problem). C When multiple sites see the same satellite, the satellite clocks can also be estimated, but at every epoch of measurement, one clock needs to be fixed or an ensemble average of cocks set to have zero mean adjustment 04/2802 12540Lec19 Differencing An alternative approach to explicit estimation is differencing data Single differences: two forms nc emanates menos drem sa sites that se Difference measurements from two satellites at the one site liminates the ground receiver cloc Double differences say eliter coins ape singled differences, but the ground and The local oscillator phases also cancel except the differer twt satellites aond woe stations s e his dierence shoulda be 12540Lec1904/28/02 12.540 Lec 19 13 Processing methods • biggest deviations in the model of GPS phase and range data. • These terms can be explicitly handled by estimation of is a very large estimation problem). Can be attacked with sequential LSQ or a Kalman filter. • When multiple sites see the same satellite, the satellite clocks can also be estimated, but at every or an ensemble average of cocks set to have zero mean adjustment. The clock and local oscillator phase variations are the clock variations (but if done brut-force in least squares epoch of measurement, one clock needs to be fixed, 04/28/02 12.540 Lec 19 14 Differencing • An alternative approach to explicit estimation is differencing data. • Single differences: two forms: satellite. Eliminates error due to satellite clock. Eliminates the ground receiver clock. • Double differences: satellites clocks are eliminated. in the number of cycles of phase between the combination of two satellites and two stations. This difference should be an integer. – Difference measurements from two sites that see the same – Difference measurements from two satellites at the one site: – By differencing a pair a single differences, but the ground and – The local oscillator phases also cancel except the differences 7