Local Height Determination Using GPS-Monitored Atmospheric Path Delays

Abstract

National satellite control points, or any fixed points determined relative to a known control point, can serve as monitoring stations when equipped with dual-frequency global positioning system (GPS) receivers. The available monitoring station coordinates are used to advantage to derive time-varying ionospheric and tropospheric path delays from the observed carrier phase data. Distinguishing atmospheric parameters from geometric positions is necessary in many cases because the relative tropospheric zenith delays are strongly correlated with the interstation height differences. In addition, GPS users may work with the single-frequency receivers that track satellite signals for only a few minutes at a time. The algorithm in this paper is based on the cosine functions of double-difference carrier phase measurements. After removing the first-order temporal and spatial ionospheric effects, the relative tropospheric delays are found to have correlation coefficients of up to 0.85, with the Saastamoinen model delays using some standard values for atmospheric pressure, temperature, and humidity. When comparing the 19 GPS-derived orthometric heights with the independently leveled heights, in a 5.5 × 4.0 km