NovAtel Inc. New Positioning Filter: Phase Smoothing in the Position Domain

摘要

During the early days of GPS navigation, Ron Hatch at Magnavox designed a filter that combined delta phase measurements and pseudoranges into a single noise reduced measurement. While reducing the noise on the measurement used in the navigation solution, the reduction of the effect of multipath was not as much as was hoped because of the biased nature of the multipath signal on the pseudorange. At the same time, the time constant in the filter had to be limited because the ionospheric phase advance was a different sign than the pseudorange ionospheric group delay error. Finally, the effectiveness of the phase smoothing technique was limited because in a kinematic environment, frequent signal outages occur and every time this happened all of the smoothed pseudorange information was lost and the accuracy of the pseudorange reverted back to its nominal unsmoothed level.