Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
1998-09-16
2001-07-03
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C342S357490
Reexamination Certificate
active
06256583
ABSTRACT:
FIELD OF THE INVENTION
The article by Eric Sutton entitled “Optimal Search Space Identification for Instantaneous Integer Cycle Ambiguity Resolution,” presented at the ION-GPS-97 Conference on Sep. 17, 1997, is herein incorporated by reference.
The present invention relates to global positioning system (GPS) attitude determining apparatus, systems and methods. More particularly, the present invention relates to instantaneous integer cycle ambiguity resolution methods, and systems and apparatus using the same.
BACKGROUND OF THE INVENTION
GPS attitude determination systems use GPS phase measurements to determine the orientation of a baseline defined by two antennas. Because antenna separation is generally greater than one wavelength, there is an integer ambiguity for each satellite that must be determined before the orientation of the baseline can be calculated. Since for attitude determination the baseline length is precisely known, the initial integer ambiguity search seeks to identify all solutions that result in a baseline length close to the true baseline length.
Integer cycle ambiguity resolution is a problem commonly encountered in GPS applications such as attitude determination and kinematic positioning. There are many recent papers on the design and performance of ambiguity resolution algorithms for kinematic positioning. Ambiguity resolution for attitude determination is different from ambiguity resolution for kinematic positioning in that for attitude determination the baseline is generally relatively short and the baseline length is very precisely known. Therefore, for attitude determination systems, the initial integer cycle ambiguity search is generally performed in solution space instead of measurement space. In other words, the initial search is based on baseline length instead of on the phase residual.
It has been shown in several recent papers that instantaneous ambiguity resolution is often possible for attitude determination systems. There are two principal design issues for ambiguity resolution: (1) Determination of the smallest possible search space from all available information and design requirements; and (2) Efficient identification of all solutions that lie in the search space. Due to the fundamental structure of the problem, an instantaneous ambiguity resolution algorithm cannot guarantee that it will produce exactly one solution, and even when exactly one solution is produced, it cannot guarantee that the solution is correct.
SUMMARY OF THE INVENTION
Disclosed are an integer cycle ambiguity resolution method, and attitude determining systems and apparatus using the same. In the method of determining a solution to an integer cycle ambiguity, four primary satellites out of a GPS satellite constellation are selected such that a number of false solutions for the integer cycle ambiguity is optimized. Next, a search space is defined such that the probability of rejecting a correct solution for the integer cycle ambiguity is guaranteed to be below a predetermined value. Next, intervals in the defined search space are searched to determine a solution to the integer cycle ambiguity. Then, attitude is determined as a function of the determined solution to the integer cycle ambiguity.
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Cuchlinski Jr. William A.
Eppele Kyle
Jensen Nathan O.
O'Shaughnessy James P.
Pipala Edward
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