Regional Ionospheric Correction for Rapid GNSS Positioning
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Solution Overview
Problem
Current navigation satellite systems (NSS) face limitations in achieving precise and rapid position estimation due to ionospheric delays and ambiguity resolution issues, leading to increased convergence times and reduced productivity in applications such as navigation, map-making, and disaster response.
Innovation Solution
The method generates regional correction information by estimating carrier phase ambiguities and computing geometric-free phase linear combinations using precise satellite data, which are then used to create ionospheric delay models for each satellite, reducing ionospheric errors and facilitating faster position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier phase measurements are used for positioning, then position precision is improved (down to centimetre-level or millimetre-level), but the convergence time increases due to the integer ambiguity problem
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing ionospheric delay models and ambiguity resolution parameters during a calibration phase using reference stations. These pre-computed corrections are then applied during real-time positioning, allowing the system to achieve centimetre-level precision without experiencing the full convergence time penalty during actual operation.
Solution Approach 2:
The patent introduces an intermediary correction system that uses reference stations to compute ionospheric delay models and ambiguity resolutions. This intermediary layer processes the complex ambiguity resolution mathematics separately, providing corrected carrier phase measurements to user receivers, thereby reducing their convergence time while maintaining high precision.
2Productivity
If code-based positioning is used, then convergence time is reduced and simplicity is maintained, but position accuracy deteriorates (approximately 15 meters)
Solution Approach 1:
The patent merges code-based and carrier phase-based positioning approaches into a combined solution. It uses code measurements for rapid initial position acquisition and convergence, then progressively incorporates carrier phase measurements with applied ionospheric corrections to achieve centimetre-level precision, thereby combining the speed advantages of code-based methods with the precision advantages of carrier phase methods.
Solution Approach 2:
The patent applies preliminary ionospheric correction computations using reference stations before user positioning. This pre-computed correction information is then applied to carrier phase measurements, enabling users to achieve high precision quickly without having to wait for the full convergence period that would normally be required for uncorrected carrier phase ambiguity resolution.
3Measurement precision
If regional correction information is generated using multiple reference stations, then ionospheric correction accuracy is improved, but system complexity and computational load increase
Solution Approach 1:
The patent segments the ionospheric correction system into regional zones, each served by a local network of reference stations. This segmentation allows each regional system to compute corrections independently with moderate complexity, while still achieving high accuracy locally. The segmentation approach distributes the computational load and avoids the need for a single complex global processing system.
Data Source
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AI summary
The invention relates to generating correction information to be used to correct observations coming from a navigation satellite system (NSS) receiver in a region of interest. For each of a plurality of reference stations in said region, raw observations obtained by the reference station observing NSS multiple-frequency signals from a plurality of satellites over multiple epochs are received (s10). Then, precise satellite information on the orbit position, clock offset, and biases of each satellite is obtained (s20). For each reference station, ambiguities in the carrier phase of the received raw observations are estimated (s30), using the precise satellite information and the position coordinates of the reference station. Geometric-free phase linear combination values are then computed (s40) based on the received raw observations together with the estimated ambiguities. The correction information is generated (s50) based on the computed geometric-free phase linear combination values. The correction information comprises, for each NSS satellite, a regional ionospheric delay function and its coefficients, those representing, per NSS satellite, the ionospheric delay in said region. The correction information is sent (s60), for example to facilitate position determination, to the NSS receiver or to a server in charge of processing observations from the NSS receiver.