TITLE:
A New Independent GPS-Free System for Geo-Referencing from Space
AUTHORS:
P. Kaufmann, P. L. Kaufmann, S. V. D. Pamboukian, R. Vilhena de Moraes
KEYWORDS:
Geo-Referencing from Space, GPS-Free Time Synchronization, Navigation and Positioning, Space Geodesy, Remote Ranging Transponder Transit Times, Propagation Path Delays
JOURNAL NAME:
Positioning,
Vol.5 No.2,
May
22,
2014
ABSTRACT: A new system’s geo-referencing from space is entirely free from any GNSS
(GPS or equivalent) systems. The system addresses to various strategic and
economic applications such as in remote clock synchronism, aircraft and balloon
navigation, missile and smart bombs tracking, satellite orbital determination
and remote target geo-positioning. The new geometry concept corresponds to an “inverted
GPS” configuration, utilizing four ground-based reference stations,
synchronized in time, installed at well known geodesic coordinates and a
repeater in space, carried by an aircraft, balloon, satellite, 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
corrected for the time delays undergone in every retransmission. A minimization
function was derived to compare the repeater’s positions referred to at least
two groups of three reference bases, to correct for the signal transit time at
the repeater and propagation delays, and consequently to provide the accurate
repeater position for each time interaction. Once the repeater’s coordinates
are known, the other determinations and applications become straightforward. The
system solving algorithm and process performance has been demonstrated by
simulations adopting a practical example with the transponder carried by an
aircraft moving over bases and a target on the ground. Effects produced by
reference clock synchronism uncertainties at the four bases on the measurements
are reviewed.