Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2002-02-19
2004-03-02
Nguyen, Tan Q. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S215000, C342S357490, C342S357490
Reexamination Certificate
active
06701253
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to navigation satellite receivers, and more particularly to methods and systems for remotely aiding the operation of navigation satellite receivers by supplying ionosphere, troposphere, relativistic effects and the satellite vehicle's bias and drift (dtsv), earth rotation, and other correction information.
DESCRIPTION OF THE PRIOR ART
Global positioning system (GPS) receivers measure signals received from several earth-orbiting satellites to determine user position and velocity, and other navigational data. Because the receiver and satellite clocks are not perfectly synchronized, such clock offset acts as an error on the distance to the satellite. The apparent distance is called the “pseudorange” (PR). The clock error can be computed by assuming all the pseudoranges to the different satellites will have the same clock offset in one measurement epoch. So four satellites are needed for a position fix, three for latitude, longitude and height or (X, Y and Z), and one for the clock offset.
Other errors on the distances to the satellites are caused by variations in the radiowave propagation speed and earth rotation. The propagation changes are caused by ionospheric and tropospheric phenomenon.
The two basic types of GPS positioning systems are real-time navigation and high-precision carrier phase positioning. Real-time navigation systems collect a minimum of four pseudorange (PR) measurements to four satellites. The PR measurements are used to solve for the three-dimensional coordinates of the receiver and the clock offset between the receiver oscillator and GPS system time. Differential GPS (DGPS) also collects the pseudorange observables, and further obtains real-time corrections for the errors inherent in the measurements.
Beacon stations have been erected to broadcast discrete real-time corrections over other radio channels and networks. Such corrections are usually specific to the local geographic area. A DGPS receiver in the local area can provide far better accuracies when its navigation solutions have benefited from such corrective information. But, each correction has conventionally required a discrete calculation. And each such calculation adds to the CPU overhead, which-costs processing time and hardware expense.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and system for providing and using real-time corrections for the errors inherent in GPS pseudorange measurements.
It is another object of the present invention to provide a method and system for improving the accuracy of navigation devices.
It is a further object of the present invention to provide a satellite-navigation system that is inexpensive.
Briefly, a navigation-satellite receiver network embodiment of the present invention comprises a server connected to the Internet to provide real-time correction information to clients. The server includes a GPS receiver that provides for tracking of a constellation of navigation satellites. When a client is online, it can receive satellite position and velocity information in the form of a polynomial coefficients. Clock, ionosphere, troposphere, and other corrections are all bundled into a second polynomial. The client therefore never computes or uses almanac or ephemeris.
Another advantage of the present invention is that a system and method are provided that lead to reduced equipment and usage costs.
REFERENCES:
patent: 6469663 (2002-10-01), Whitehead et al.
patent: 6567041 (2003-05-01), O'Dell
Edwards Stephen J.
McBurney Paul W.
Eride, Inc.
Nguyen Tan Q.
LandOfFree
Total correction strategy does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Total correction strategy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Total correction strategy will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3204810