Signal Transceiver Transit Times and Propagation Delay Corrections for Ranging and Georeferencing Applications

Abstract

The changes in phase, time and frequency suffered by signals when retransmitted by a remote and inaccessible transponder and the propagation delays are major constraints to obtain accurate ranging measurements in various related applications. We present a new method and system to determine these delays for every single pulsed signal transmission. The process utilizes four ground-based reference stations, synchronized in time and installed at well known geodesic coordinates. The repeater station is located within the fields of view common to the four reference bases, such as in a platform transported by a satellite, balloon, aircraft, etc. Signal transmitted by one of the reference bases is retransmitted by the transponder, received back by the four bases, producing four ranging measurements which are processed to determine uniquely the time delays undergone in every retransmission process. The repeater's positions with respect to each group of three out of four reference bases are given by a system of equations. A minimization function is derived comparing repeater's positions referred to at least two groups of three reference bases. The minimum found by iterative methods provide the signal transit time at the repeater and propagation delays, providing the correct repeater position. The method is applicable to the transponder platform positioning and navigation, time synchronization of remote clocks, and location of targets. The algorithm has been fully demonstrated simulated for practical situation with the transponder carried by an aircraft moving over bases on the ground. The errors of the determinations have been evaluated for uncertainties in clock synchronization, in propagation time delays and other system parameters.

A New Independent GPS-Free System for Geo-Referencing from Space

“…With a time signals transmitting site located at base A, the other reference bases B, C, D and a target in P, the segments measurements obtained are [12]: …”

“…Details on the software description, using MATLAB, version R2010a [15] has been given elsewhere [12] [14].…”

Geolocal – A New System for Geo-Referencing: Analysis of Base Distribution

“…Following this trend, Brazil also has a work group developing a navigation system intended to be independent of current satellite systems without necessarily using navigation satellites for its purpose, named Geolocal. This new navigation system was conceived and patented by researchers of Mackenzie University (Kaufmann and Levit Kaufmann, 2012; Kaufmann et al, 2012, 2014; Pamboukian, 2012) and it is currently under the first phase of implementation.…”