Exploration system and method for high-accuracy and high-confidence level relative position and velocity determinations
First Claim
1. A mobile fleet exploration system for obtaining high accuracy relative earth position and velocity determinations amongst individual mobile units in the fleet from a plurality of GPS receiving stations distributed throughout the mobile fleet, the exploration system comprising:
- at least one outlying individual mobile unit including means for obtaining a first time-sequence of pseudo-ranges and pseudo-range-rates to a plurality of GPS satellites;
a main mobile unit including means for obtaining a second time-sequence of pseudo-ranges and pseudo-range-rates to said plurality of GPS satellites;
navigation computer means for calculating a plurality of relative earth positions and velocities from an input comprising a sequence of delta-pseudo-ranges and delta-pseudo-range-rates relative to said plurality of GPS satellites derived from the respective pseudo-ranges and pseudo-range-rates relative to said individual mobile fleet units and said main mobile unit and including a Kalman filter for filtering said delta-pseudo-ranges using information from said delta-pseudo-range-rates;
associative means for pairing each pseudo-range in said first and second time-sequences of pseudo-ranges with a time-code indicating a time each respective pseudo-range was obtained;
communication means for transferring said first and second time sequences of pseudo-ranges to the navigation computer means and associative means; and
differencing means for time-aligning according to said time code and subtracting the corresponding pseudo-ranges and pseudo-range-rates of said first time-sequence of pseudo-ranges and pseudo-range-rates from said second time-sequence of pseudo-ranges and pseudo-range-rates to produce a sequence of delta-pseudo-ranges and delta-pseudo-range-rates and for communicating said delta-pseudo-ranges and delta-pseudo-range-rates to the navigational computer means wherein a difference in relative positions and velocities amongst the individual mobile fleet units can be determined.
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Accused Products
Abstract
An embodiment of the present invention is a shipboard GPS positioning system having data links to outlying tailbuoys equipped with respective GPS receivers. On ship, an Intel 386-based microcomputer system collects data from various ship'"'"'s equipment including the ship'"'"'s GPS receiver and data from the several tailbuoy units. A computer-implemented process located in the microcomputer system controls the following processes. Periodically each GPS receiver produces updated pseudo ranges (PRs) and these are time-tagged. The time-tagged PRs for the ship are aligned according to their time tags with their counterpart PRs from the tailbuoys. The raw PRs are then passed through a Kalman mathematical filter to produce filtered pseudo-ranges (PRs). A position solution is then attempted for each GPS receiver using the PRs. The filters provide statistical data that is used to rate the quality of each PR in a weighted least squares solution process. Special measures are included to provide quality control/quality assurance, including the use of error ellipses on the display to present a graphic indication of expected solution accuracy, and the use of real time fault detection, isolation, and correction algorithms when redundant satellite information is available.
456 Citations
10 Claims
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1. A mobile fleet exploration system for obtaining high accuracy relative earth position and velocity determinations amongst individual mobile units in the fleet from a plurality of GPS receiving stations distributed throughout the mobile fleet, the exploration system comprising:
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at least one outlying individual mobile unit including means for obtaining a first time-sequence of pseudo-ranges and pseudo-range-rates to a plurality of GPS satellites; a main mobile unit including means for obtaining a second time-sequence of pseudo-ranges and pseudo-range-rates to said plurality of GPS satellites; navigation computer means for calculating a plurality of relative earth positions and velocities from an input comprising a sequence of delta-pseudo-ranges and delta-pseudo-range-rates relative to said plurality of GPS satellites derived from the respective pseudo-ranges and pseudo-range-rates relative to said individual mobile fleet units and said main mobile unit and including a Kalman filter for filtering said delta-pseudo-ranges using information from said delta-pseudo-range-rates; associative means for pairing each pseudo-range in said first and second time-sequences of pseudo-ranges with a time-code indicating a time each respective pseudo-range was obtained; communication means for transferring said first and second time sequences of pseudo-ranges to the navigation computer means and associative means; and differencing means for time-aligning according to said time code and subtracting the corresponding pseudo-ranges and pseudo-range-rates of said first time-sequence of pseudo-ranges and pseudo-range-rates from said second time-sequence of pseudo-ranges and pseudo-range-rates to produce a sequence of delta-pseudo-ranges and delta-pseudo-range-rates and for communicating said delta-pseudo-ranges and delta-pseudo-range-rates to the navigational computer means wherein a difference in relative positions and velocities amongst the individual mobile fleet units can be determined. - View Dependent Claims (2, 3, 4, 5)
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6. A method for obtaining high accuracy relative earth position and velocity determinations amongst individual mobile units in a fleet from a plurality of GPS signals received at stations distributed throughout the mobile fleet, the method comprising the steps of:
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obtaining a first time-sequence of pseudo-ranges and pseudo-range-rates to a plurality of GPS satellites from at least one outlying individual mobile unit; obtaining a second time-sequence of pseudo-ranges and pseudo-range-rates to said plurality of GPS satellites from a main mobile unit; calculating a plurality of relative earth positions and velocities with a navigation computer from an input comprising a sequence of delta-pseudo-ranges and delta-pseudo-range-rates relative to said plurality of GPS satellites derived from respective pseudo-ranges and pseudo-range-rates relative to said individual mobile fleet units and using a Kalman filter to filter said delta-pseudo-ranges with information from said delta-pseudo-range-rates; pairing each pseudo-range in said first and second time-sequences of pseudo-ranges in an associative means with a time-code indicating a time each respective pseudo-range was obtained; communicating said first and second time sequences of pseudo-ranges to said navigation computer and associative means; and time-aligning according to said time code and subtracting corresponding pseudo-ranges and pseudo-range-rates of said first time-sequence of pseudo-ranges and pseudo-range-rates from said second time-sequence of pseudo-ranges and pseudo-range-rates in a differencing means to produce a sequence of delta-pseudo-ranges and delta-pseudo-range-rates and for communicating said delta-pseudo-ranges and pseudo-range-rates to said navigational computer wherein a difference in relative positions and velocities amongst the individual mobile fleet units can be determined. - View Dependent Claims (7, 8, 9, 10)
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Specification