Courses - GPS 571
GPS 571 Precise Point Positioning
(catalog description): Pseudorange and carrier phase
observables, satellite time, relativity, broadcast and precise
ephemerides, range iteration, receiver and satellite clock errors;
singularities, tropospheric refraction and absorption, impact of
the ionosphere, solid earth tides, ocean loading, satellite
antenna offset, phase windup correction, closed form solutions;
Kalman filter; timing, mapping of the spatial and temporal
variation of the troposphere and ionosphere. Prerequisite: GPS 401
and 441, MAT 262 and 332, equivalent, or consent, Lec. 1, Cr.
1
The pseudorange and carrier phase
equations will be discussed term by term, including receiver and
satellite clock errors, phase ambiguities, hardware delays and
signal multipath at the receiver and at the satellite.
Considerable details will be provided on the physics of the
troposphere and ionosphere and their impact on pseudoranges and
carrier phases.
The point positioning solution
using the broadcast ephemeris and pseudorange observations to four
and more satellites from a single station will be given in both
the linearized and closed forms. We accurately compute the
topocentric distance which the signals travel from the epoch of
transmission at the satellite to the epoch of reception at the
receiver antenna, taking the finite travel time of light and the
earth's rotation into account.
The core of this unit is Precise
Point Positioning (PPP) from dual-frequency pseudorange and
carrier phase observations using the precise ephemeris and
satellite clock corrections. Because PPP potentially gives
centimeter accurate geocentric coordinates it is necessary to deal
with solid earth tides and ocean loading. The phase windup
correction, resulting form the right circular polarization of the
satellite signals, does not cancel and must be considered.
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