When three satellites for passive location are used, if the height of terrain where the target locate changes greatly and the
height is assumed constant the height error will be increased. So the Least-square estimation method is presented, at the
same time in the process of algorithm iteration the target height can be inquired in the geography information system and
be corrected continuously, and the localization error is analyzed and simulated, the result indicates that the corrected
height error can improve the height precision, then improve the level precision, the improved the level precision will
improve the height precision, then the integral localization precision can be improved.
Expatiate on method of transmitting data and voice in service channel; with the sync principle of time division system, it manages to transmit voice and data in one line and some schemes are designed. The hardware of one scheme is also made. The product's performance is good and can satisfy designing requirement after tested. The schemes given in this paper has merits of simple circuit, easy realization and stable work. So it has some use value.