GPS BDS Carrier Differential Positioning Inter-System Bias
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Solution Overview
Problem
Current multi-GNSS tight combined positioning methods face challenges in handling different frequencies between satellite systems like GPS and BDS, leading to instability in carrier difference inter-system biases and limited positioning accuracy.
Innovation Solution
A GPS/BDS tight combined carrier differential positioning method is developed, which constructs an inter-system double-difference model, performs parameter decorrelation, and uses a fixed ambiguity to achieve continuous estimability of the carrier difference inter-system bias, enabling high-precision positioning by forming an ionosphere-free combination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tight combined model of common reference satellite is used for inter-system difference positioning, then positioning accuracy is improved, but it becomes difficult to eliminate hardware delay due to different signal modulation modes, requiring extraction of difference inter-system bias as prior information
Solution Approach 1:
The patent segments the inter-system difference model into intra-system difference components and inter-system bias components. By processing GPS and BDS systems separately first (intra-system), then combining their results (inter-system), the complex task of eliminating hardware delays is divided into manageable segments that can be handled independently.
Solution Approach 2:
The patent introduces an intermediary parameter (difference inter-system bias) that mediates between the GPS and BDS systems. This bias parameter acts as a bridge that allows the tight combined model to function without directly confronting the incompatible hardware delays of different signal modulation modes.
2Device complexity
If a differential positioning algorithm studying only the same frequency between systems is used, then the algorithm is simpler, but it is not conducive to give full play to the advantages of multi-GNSS combined positioning when different frequencies are encountered
Solution Approach 1:
The patent creates a universal algorithm framework that can handle both same-frequency and different-frequency satellite combinations. The model is designed to be multi-functional, automatically adapting to whatever frequency combinations are available in the observed satellite data, whether GPS-GPS, BDS-BDS, or GPS-BDS pairs.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the frequency combination parameters based on the available satellites. When same-frequency satellites are available, the algorithm uses those combinations; when only different-frequency satellites are available, it switches to handling inter-frequency biases, thus maintaining versatility across different operational conditions.
3Device complexity
If carrier difference inter-system bias is not continuously estimable, then the positioning model is simpler, but the reliability of tight combined positioning is reduced
Solution Approach 1:
The patent ensures continuous estimation of the carrier difference inter-system bias by maintaining the bias parameter throughout the positioning process. Rather than computing the bias only when needed, the model continuously updates and utilizes the bias parameter across all epochs and satellite combinations, ensuring uninterrupted reliability.
Solution Approach 2:
The patent implements a feedback mechanism where the estimated carrier difference inter-system bias from previous epochs informs the bias estimation in current epochs. This continuous feedback loop allows the model to maintain reliable bias estimates even when satellite visibility changes, by using past estimation results to constrain and guide current estimations.
Data Source
AI summary
A tightly combined GPS/BDS carrier differential positioning method is provided. The method comprises: using a GPS as a reference system to construct a GPS intra-system double-difference ionosphere-free combination model and a GPS/BDS inter-system double-difference ionosphere-free combination model; selecting a BDS reference satellite to re-parameterize an ambiguity of a GPS/BDS inter-system double-difference ionosphere-free combination and perform parameter decorrelation, estimating an ionosphere-free combination carrier differential inter-system bias in real time, and performing reference conversion on the ionosphere-free carrier inter-system bias to realize a continuous estimability of the ionosphere-free carrier differential inter-system bias in necessary; and finally, using ambiguity-fixed base carrier observations to form the ionosphere-free combination and performing tightly combined positioning on the inter-system double-difference ionosphere-free combination based on the estimated ionosphere-free carrier difference inter-system bias.