The Effect of the Anomalous Gravity on the Direction of the Vertical as Determined by a Mechanically Perfect Inertial Platform

摘要

The error of mechanization in an inertial platform system due to the assumption that the earth has a normal gravity field is studied in this report. The effect of this mechanization error on the determination of the direction of the vertical is emphasized. A system of linear differential equations, which was originally developed by Broxmeyer, l964, is adapted to the study of the effect of the anomalous gravity on the inertially determined vertical. Six different simulations are conducted for periods of 25 hours. The inertially determined vertical is found, for all cases, to deviate from the direction of the plumb line by a maximum angular value equal to the total deflection angle of the plumb line from the normal to the ellipsoid. The gravity anomaly is found to have a secondary effect on the results. Hence a smoothed value for the gravity anomaly along the flight path of the navigator might be sufficient for the mechanization problem of the inertial platform system. Also the use of the astro-geodetic components of the deflection of the vertical on the geoid seems to be the simplest way in computing the different components of the gravity affecting the accelerometers of the inertial platform system without adding any serious problems to the computer of the inertial platform system. (Author)