A scheme for reducing the effect of selective availability on precise geodetic measurements from the Global Positioning System

摘要: From March to August 1990, the signals transmitted by Block II satellites of Global Positioning System (GPS) were dithered under a policy “Selective Availability” (SA). The dithering appears as ∼10−10 deviation satellite oscillator frequency, which, when accumulated over several minutes, can produce an error ∼100 cycles (∼20 m) in model for carrier beat phase. Differencing between simultaneously sampling receivers minimizes error. If, however, do not sample simultaneously, it is necessary frequency deviation, which we estimate from phase observed at station with stable local oscillator. We apply such data collected 1990 TI4100 and Minimac times separated 0.92 s. Applying algorithm significantly improves root mean square (RMS) scatter estimated relative position vectors. RMS set including similar both non-simultaneously receivers, result indicates that SA be adequately modeled.