GNSS Carrier Phase Differencing for Multipath Detection
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Solution Overview
Problem
Existing Global Navigation Satellite System (GNSS) position estimation methods face challenges in accurately determining receiver positions due to multipath effects, which are not effectively detected without resolving all carrier phase ambiguities, especially when the positions of different receivers are unknown.
Innovation Solution
The method involves taking a difference between carrier phases measured by multiple receivers to estimate an integer ambiguity difference, which serves as an index for detecting multipath, allowing for position estimation using code or carrier signals without fully resolving carrier phase ambiguities. This integer ambiguity difference is tracked over time to detect impulse changes, and its variance is used to identify multipath, enabling the rejection of satellites causing inaccuracies in position estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier phase measurements are used for position estimation, then measurement precision is improved, but carrier phase ambiguities cause errors in position calculation
Solution Approach 1:
The patent introduces an intermediary variable called 'integer ambiguity difference' that mediates between the high-precision carrier phase measurements and the unknown integer ambiguities. By taking the difference between carrier phase measurements from multiple receivers, the patent creates a new observable that retains the high precision benefits while eliminating the problematic integer ambiguities, thus resolving the contradiction between measurement precision and reliability
Solution Approach 2:
The patent transforms the original carrier phase measurement parameter by applying a differential operation. Instead of using the absolute carrier phase values which contain unknown integer ambiguities, the patent changes the parameter to the difference between carrier phases measured by different receivers. This parameter transformation eliminates the ambiguous integer components while preserving the high-precision differential information needed for accurate position estimation
2Measurement precision
If integer ambiguity resolution is performed to eliminate carrier phase ambiguities, then position estimation accuracy is improved, but device complexity and computational requirements increase
Solution Approach 1:
The patent extracts and removes the problematic integer ambiguity components from the carrier phase measurements by applying a differential operation between multiple receivers. Instead of attempting to resolve the unknown integer ambiguities through complex computational methods, the patent simply extracts and eliminates them by taking differences, thereby achieving accurate position estimation without requiring complex ambiguity resolution systems
Solution Approach 2:
The patent applies partial action by not attempting to fully resolve all carrier phase ambiguities. Instead of performing complete integer ambiguity resolution which would require complex systems and computations, the patent applies a simpler differential operation that partially processes the measurements to eliminate the ambiguous components, achieving sufficient accuracy without excessive complexity
3Reliability
If multiple receivers are used to detect multipath through carrier phase differencing, then multipath detection capability is improved, but loss of information occurs due to unknown receiver positions
Solution Approach 1:
The patent introduces the integer ambiguity difference as an intermediary that enables multipath detection without requiring knowledge of absolute receiver positions. By using the difference between carrier phase measurements as the basis for detection, the patent creates a new observable that is independent of the unknown position information, thus improving multipath detection capability while avoiding the loss of information problem
Data Source
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AI summary
The present invention relates to a positioning system for global navigational satellite system (GNSS) includes a first receiver to measure a first carrier phase of a carrier signal emitted by a satellite and a second receiver to measure a second carrier phase of the carrier signal emitted by the satellite. The, first carrier phase includes a first carrier phase ambiguity as an unknown integer number of wavelengths of the carrier signal travelled between the satellite and the first receiver. Similarly, the second carrier phase includes a second carrier phase ambiguity as an unknown integer number of wavelengths of the carrier signal travelled between the satellite and the second receiver. The GNSS includes a processor to determine an integer ambiguity difference between the first carrier phase ambiguity and the second carrier phase ambiguity from a difference in the measurements of the first carrier phase and the second carrier phase and to detect a multipath of the carrier signal based on a value of the integer ambiguity difference and tracked set of integer ambiguity differences.