Reduced-power GPS-based system for tracking multiple objects from a central location

Abstract

Location of an object to be tracked is determined by measuring, at a receiver situated at the object, the propagation time differences between the signals from a plurality of GPS satellites, each of which is received by the receiver situated at the object. The measured propagation time difference values are transmitted to a central station where the location of the object to be tracked is calculated based upon the propagation time differences of the signals transmitted from the satellites and data derived from a receiver apart from the object but also receiving signals from the satellites.

Description

[0001]This application is a continuation of application Ser. No. 08 / 465,229 filed May 31, 1995 now abandoned.FIELD OF THE INVENTION[0002]This invention relates to object tracking systems used to locate and track multiple terrestrial (including water-based) objects and, more particularly, to power efficient object tracking systems based upon information obtained from satellites.BACKGROUND OF THE INVENTION[0003]The tracking and location of assets such as railcars, shipping or cargo containers, trucks, truck trailers, automobiles, etc. can be highly advantageous in commerce. Precise tracking of such vehicles and objects can facilitate their being allocated and positioned in an efficient manner, and can provide for immediate, accurate localization of lost, delayed or damaged assets. The space-based global positioning system (GPS) implemented by the United States Department of Defense constitutes a convenient instrumentality for determining geographical position in real time.[0004]The GP...

AI Technical Summary

Benefits of technology

"The invention is a method for identifying the location of an object or asset by measuring the time differences between signals from multiple GPS satellites and transmitting the data to a central station. The system uses a reduced-power GPS-based system that consumes less power and has lower processing complexity than standard GPS receivers. The system also requires minimal energy at the tracked assets and can track multiple objects simultaneously. The technical effects of the invention include reduced power consumption, lower processing complexity, and improved efficiency for GPS-based asset tracking."

Problems solved by technology

With receiver noise and imperfect knowledge of satellite positions, the receiver-satellite ranges can only be estimated.

Any error in satellite and receiver clock synchronization leads to proportional range errors.

However, the full position determination is not made at the railcar.

This consumes significant power.

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