GNSS Pseudorange Correction for Solar-Triggered Ionospheric Errors
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Solution Overview
Problem
Existing GNSS receivers face challenges in accurately compensating for ionospheric errors in pseudo-range measurements, particularly during abnormal solar activity, as current methods like Klobuchar/Nequick models and SBAS provide insufficient granularity and Iono-Free Linear Combination introduces noise, while dual frequency receivers are limited by availability and urban interference.
Innovation Solution
A method that dynamically adjusts ionospheric error correction by performing Ionospheric Free Linear Combination (IFLC) only when solar activity exceeds a threshold, using a combination of GPS bands L1 and L5, and incorporates checks for latitude, day-time, and urban environment to optimize accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Ionosphere Free Linear Combination (IFLC) is used to eliminate ionospheric errors, then ionospheric error compensation is improved, but measurement noise increases
Solution Approach 1:
The system dynamically switches between IFLC mode and standard processing mode based on real-time ionospheric activity conditions. When ionospheric disturbance exceeds a threshold, IFLC is activated to eliminate errors; otherwise, standard processing is used to maintain lower noise levels. This dynamic adaptation resolves the contradiction by applying the noise-intensive IFLC only when necessary.
2Measurement precision
If dual frequency receivers are used to cancel ionospheric error, then position accuracy is improved in bad ionospheric conditions, but performance deteriorates in good solar conditions due to additional noise
Solution Approach 1:
The system dynamically adjusts the processing mode based on solar activity levels. During periods of high solar activity with degraded ionospheric conditions, dual-frequency IFLC processing is activated to maximize position accuracy. During normal solar conditions, the system switches to standard single-frequency processing to avoid the performance degradation caused by unnecessary dual-frequency noise.
3Measurement precision
If Klobuchar/Nequick models are used for ionospheric correction, then 50-70% of errors are cancelled in normal solar activity, but they cannot cope with nonstandard ionospheric behavior caused by abnormal solar activity
Solution Approach 1:
The system dynamically evaluates ionospheric activity indicators and switches processing modes accordingly. When indicators show abnormal solar activity, the system transitions from standard Klobuchar/Nequick model processing to IFLC processing, enabling adaptation to nonstandard ionospheric behavior while maintaining the simplicity and effectiveness of standard models during normal conditions.
4Measurement precision
If SBAS systems are used for ionospheric compensation, then area-optimized corrections are provided, but they cannot respond to rapid changes in ionospheric conditions due to daily time granularity
Solution Approach 1:
The system performs preliminary evaluation of ionospheric activity indicators and proactively switches to IFLC processing mode before significant positioning errors occur. By continuously monitoring solar activity parameters and predicting ionospheric disturbance trends, the system prepares and activates the appropriate processing mode in advance, overcoming the slow response time of SBAS systems that only update daily.
Data Source
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AI summary
A method for performing a correction of a ionospheric error affecting pseudo-ranges measurements in a GNSS receiver comprising in a navigation processing procedure performed at a GNSS receiver receiving pseudo range measurements previously calculated by said GNSS receiver obtained from a first carrier signal and a second carrier signal in said satellite signals, performing a correction procedure of said pseudo-range measurements comprising applying to said pseudo-range measurements corrections for predictable errors obtaining corrected pseudo-ranges and applying (15) to said corrected pseudo-range measurements a further ionospheric error correction calculation to obtain further ionospheric error correction values, and performing a position calculation operation (14) processing said corrected pseudo-range measurements and said ionospheric error correction values and outputting position, velocity and time information (PVT) of the GNSS receiver. Said applying to said corrected pseudo-ranges comprises a further ionospheric error correction calculation to obtain further ionospheric error correction values and supplying it to said position calculation operation only, otherwise performing (17) a standard ionospheric error correction derived from GNSS navigation data, in particular by Klobuchar/Nequick models and/or SBAS.