Cooperative Estimation Algorithms Using TDOA Measurements

Abstract

A navigation algorithm using Time Difference of Arrival (TDOA) measurements obtained from signals of opportunity (SOPs) is developed. SOP-derived TDOA measurements are signals that are transmitted for purposes other than navigation (such as communication, telecasts, etc.) and are motived as appealling alternatives to GPS. In the scenario considered herein, the received SOPs are generated by asynchronous emitters at known locations. The measured TDOA are with reference to a reference receiver also at a known location. Although it would appear that the equations governing TDOA measurements, and consequently TDOA GDOP, are quite different from their GPS counterparts, it is shown that the TDOA measurement equations can be transformed into GPS pseudorange equations. This interpretation not only provides a direct evaluation of the TDOA GDOP and affords a characterization of the optimal measurement geometry, but, in addition, lets us fall back on well known GPS algorithms.