On Ultrahigh-Precision GPS Positioning and Navigation

This paper introduces an ultrahigh-performance GPS positioning and navigation system for gantry crane auto-steering. The system differs from conventional systems in terms of the achievable positioning accuracy and precision. Aside from ambiguity resolution and reliability, many error sources (such as phase wrap-up, antenna phase-center variation, instrumental group delay bias, receiver clock jumps, and residual tropospheric delay.) must be handled precisely to attain ultrahigh-precision positioning solutions. The paper also introduces an optimal interfrequency carrier-phase linear combination of the L1 and L2 measurements that can reduce the effects of quasirandom errors (that is, errors including significant low-frequency components and showing to some extent random behavior over relatively short intervals of time), such as multipath, diffraction, and ionospheric scintillation. A practical approach to estimating realistic receiver system noise is also introduced.