Partial Search Integer Ambiguity Resolution
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Solution Overview
Problem
Current GPS RTK systems face challenges in resolving integer ambiguities, especially in urban environments and at longer ranges, due to multipath errors and unmodeled systematic biases, leading to prolonged ambiguity re-initialization times.
Innovation Solution
A partial search method is employed to quickly resolve integer ambiguities by selecting likely ambiguity combinations using floating ambiguities, reducing the set of ambiguities that fail predefined criteria, and applying the LAMBDA method for efficient computation, suitable for GPS receivers with limited microprocessor capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a full search method is used to resolve integer ambiguities, then the reliability of ambiguity resolution improves, but the computation time and processing power required increase significantly
Solution Approach 1:
The patent segments the ambiguity resolution process into two phases: a quick partial search phase that tests a limited subset of candidate ambiguity combinations, and a more thorough validation phase. This segmentation allows the system to quickly eliminate obviously incorrect solutions without performing a complete exhaustive search, thereby reducing computation time while maintaining reliability through the validation step.
Solution Approach 2:
The patent applies partial action by performing an incomplete but sufficient search through the ambiguity candidate space. Instead of exhaustively testing all possible ambiguity combinations, the system tests a partial set of most-likely candidates based on floating ambiguity values and selects the first valid solution found, which is sufficient for practical applications and dramatically reduces computation time.
2Area of stationary object
If the receiver separation distance increases, then the coverage area improves, but the distance-dependent biases grow making reliable ambiguity resolution more difficult
Solution Approach 1:
The patent performs preliminary processing of the ambiguity candidates by sorting them according to their likelihood based on floating ambiguity values before conducting the search. This preliminary arrangement ensures that the most probable ambiguity combinations are tested first, increasing the probability of finding a valid solution even in challenging long-baseline conditions where errors are more significant.
Solution Approach 2:
The patent changes the search strategy parameter from exhaustive to selective based on the quality indicators of candidate ambiguities. By using the float ambiguity values as a guide to prioritize which integer candidates to test, the system adapts the search process to the actual measurement quality, maintaining reliability across varying baseline distances.
3Measurement precision
If a comprehensive ambiguity search is performed, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent extracts and utilizes the floating ambiguity values as a guide to identify the most likely integer ambiguity candidates. By taking out only the necessary subset of candidates for testing rather than processing all possible combinations, the system achieves high measurement precision while keeping the processing complexity manageable through this extraction and selection mechanism.
Data Source
AI summary
A method for performing integer ambiguity resolution in a global navigation satellite system is disclosed. A set of ambiguities, which are associated with carrier phase measurements of at least some of the signals received from the satellites in an identified set of satellites, are identified. Integer ambiguities are estimated and a best candidate set and a second best candidate set of integer ambiguity values are determined. Upon determining that the best set of integer ambiguity values fail to meet a discrimination test, each ambiguity for which integer ambiguity values in the best candidate set and second best candidate set fail to meet predefined criteria are removed from the set of ambiguities to produce a reduced set of ambiguities. The integer ambiguities in the reduced set of ambiguities are then resolved and an output is generated in accordance with the resolved integer ambiguities.