GPS Satellite Surveying, 4th Edition

6.3 Navigation Solution

The navigation solution, also frequently referred to simply as point positioning, is the type of solution the GPS system was originally designed for, achieving position accuracy of about 1m. The solution is available at any time, depending of course on satellite visibility, anywhere on earth. This solution is frequently implemented in nonsurveying products, such as general consumer products or low-accuracy hand-held receivers, or is executed in the background as part of more elaborate solutions.

The navigation solution estimates the receiver coordinates, of course understood to be the receiver antenna coordinates and the receiver clock error using pseudorange observables. Carrier phases can be used to smooth the pseudoranges. There are several simplifying assumptions. The satellite positions at signal transmission times are assumed known and available from the broadcast ephemeris. The satellite clock corrections are also assumed to be available from the navigation message and must be applied to the observations. As discussed in Section 6.2.2, the satellite clocks are monitored by the control center, which models the clock offsets in terms of polynomials in time, and provides an estimate for the time group delay and the intersignal correction. The navigation solution does not estimate a separate satellite clock error. The ionospheric and tropospheric delays are also computed from models as explained in Chapter 8 and applied to the observations, and the ...