Precise point positioning (PPP) methods are generally considered to
be point solution methods using undifferenced code and carrier phase
measurements. Since the measurements are undifferenced, a means of
reducing systematic errors in the measurements is generally used.
Precise orbit and satellite clock values from IGS or other organizations
are most often used to reduce system biases. PPP methods promise
decimeter level positioning or better in stand-alone operation. Many
PPP methods rely on code phase. These methods are subject to code
multipath and hence typically use long smoothing filters and L1/L2
measurements to reduce multipath. As a result, these methods take
a long time to converge to decimeter level accuracies. However, once
they do converge, they provide the means for kinematic applications.
Other PPP methods are carrier phase only methods. Some of these methods
are attempting various types of ambiguity resolution. These show
some promise and are providing interesting results. At SRI International,
we often have need to provide a stationary survey in an environment
that may have very high multipath. We are interested in rapidity
of convergence of stand-alone carrier phase positioning methods.
We use an IGS rapid ephemeris. This paper describes a carrier phase
only solution based on a method derived from weighted batch least
squares. Preliminary results show reliable sub-decimeter positioning
after six hours. We attempt to quantify the error behavior as the
settling time is decreased. Results are compared with several alternative
precise positioning methods. Also discussed are the numerical stability
issues associated with methods of this type. The phase only method
we derive is compared with several carrier smoothed code methods.
The data used are from SPS receivers as well as from a PPS receiver.
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