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The changes in phase, time and frequency suffered by signals whenretransmitted by a remote and inaccessible transponder and the propagationdelays are major constraints to obtain accurate ranging measurements in variousrelated applications. We present a new method and system to determine thesedelays for every single pulsed signal transmission. The process utilizes fourground-based reference stations, synchronized in time and installed at wellknown geodesic coordinates. The repeater station is located within the fieldsof view common to the four reference bases, such as in a platform transportedby a satellite, balloon, aircraft, etc. Signal transmitted by one of thereference bases is retransmitted by the transponder, received back by the fourbases, producing four ranging measurements which are processed to determineuniquely the time delays undergone in every retransmission process. Therepeater's positions with respect to each group of three out of four referencebases are given by a system of equations. A minimization function is derivedcomparing repeater's positions referred to at least two groups of threereference bases. The minimum found by iterative methods provide the signaltransit time at the repeater and propagation delays, providing the correctrepeater position. The method is applicable to the transponder platformpositioning and navigation, time synchronization of remote clocks, and locationof targets. The algorithm has been fully demonstrated simulated for practicalsituation with the transponder carried by an aircraft moving over bases on theground. The errors of the determinations have been evaluated for uncertaintiesin clock synchronization, in propagation time delays and other systemparameters.

Signal transceiver transit times and propagation delay corrections for ranging and geo-referencing applications