Researches On The Exaltation Accuracy Of Differential Global Positioning System

Pseudo-range differential GPS is one of the most widely-used differential GPS positioning techniques at the present time. Along with the increase of the distance between the moving station and the base station, the larger the pseudo-range remaining error caused by ephemeris error is, the lower the corresponding positioning accuracy will be in the case of pseudo-range DGPS positioning. On the other hand, due to the difference of the routes by which the waves transmitted by the satellites pass through the base station and the ionosphere and the troposphere above the users, and also the difference of the environment, etc, namely the incoherence residing between the user and the base station, there are remaining errors in the correction of the pseudo-range and the rate of change broadcast by the base station. The errors prove to be smaller when the users approach the base station, however, they become larger owing to the increasing of the distance and the weakening of the relativity.It is essential to make fine distinction among the three kinds of error and to process respectively about their different characteristics when improving the precision of DGPS. Thereinto, the pseudo-range remaining error caused by ephemeris error is concerned with the relative position between the observation station and the base station. So we discussed the relationship between them and investigated the method which makes use of differential GPS positioning techniques to weaken the ephemeris error.The thesis briefly introduces our aim and the significance of the research, and also the background at home and abroad. We present in the second and the third parts the fundamental principles of GPS-positioning and the technique of DGPS. On this basis, it is analyzed in the fourth part that why the ephemeris error could not be removed in the pseudo-range DGPS positioning, including the relationship between the ephemeris error and the observation station. Furthermore, a new reference value is introduced as the quadratic difference correction of distance and is showed as the error of pseudo-range measurement caused by the ephemeris error. While in the fifth part, we explore the geometric significance and the basic characteristic of the quadratic difference correction of distance, and the relationship among the corrections of the multiple observation stations as well. Finally, we find out through the simulated experiments that it is true and accurate for the functional relations between the quadratic difference correction of distance and the error of pseudo-range measurement caused by the ephemeris error.