GNSS Pseudorange Correction for Ionospheric Noise Trade-Offs
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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 suboptimal results due to their global nature or increased noise in dual frequency combinations.
Innovation Solution
A method for correcting ionospheric errors in GNSS receivers using a combination of L1 and L5 carrier signals, involving an ionospheric free linear combination (IFLC) when solar activity exceeds a threshold, and standard corrections otherwise, with additional checks for latitude, day-time, and urban environment to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual frequency combination (L1 and L5) is used to cancel ionospheric error, then ionospheric error correction is improved, but measurement noise increases
Solution Approach 1:
The system dynamically changes the processing parameter by switching between dual-frequency ionosphere-free combination and single-frequency measurements based on the detected ionospheric activity level. When ionospheric disturbance exceeds a threshold, the dual-frequency combination is applied; otherwise, single-frequency measurements are used to avoid unnecessary noise
Solution Approach 2:
The system implements dynamic adaptation by continuously monitoring ionospheric conditions and adjusting the measurement processing strategy in real-time. The ionospheric activity indicator is calculated and used to dynamically switch between different correction approaches, making the system responsive to changing environmental conditions
2Adaptability or versatility
If Klobuchar/Nequick models are used for ionospheric correction, then global compatibility is improved, but regional accuracy deteriorates
Solution Approach 1:
The system applies local quality by using region-specific ionospheric models (such as Nequick for Europe) when ionospheric activity is high, rather than relying solely on global models. This allows the correction to be tailored to regional characteristics while maintaining the ability to switch to global models when appropriate
3Measurement precision
If SBAS systems are used for ionospheric correction, then regional optimization is improved, but responsiveness to sudden solar activity deteriorates
Solution Approach 1:
The system implements feedback by continuously monitoring ionospheric conditions through multiple indicators (TEC, virtual height, scintillation indices) and using this information to adjust the correction strategy in real-time. This closed-loop approach enables rapid response to sudden solar activity changes, overcoming the delayed response of SBAS systems
4Measurement precision
If ionosphere-free linear combination is always applied, then ionospheric error cancellation is improved, but noise and environmental interference increase
Solution Approach 1:
The system applies partial action by using the ionosphere-free linear combination only when and where needed (during periods of high ionospheric activity), rather than continuously. This selective application minimizes the introduction of noise and environmental interference while still providing correction when necessary
Data Source
AI summary
A method corrects an ionospheric error affecting pseudo-range measurements in a GNSS receiver receiving a plurality of satellite signals from a plurality of satellites of the constellation of satellites. The method is performed in a navigation processing procedure performed at a GNSS receiver, receiving pseudo-range measurements previously calculated by the GNSS receiver obtained from a first carrier signal and a second carrier signal in the satellite signals, in particular in GPS bands L1 and L5. The method includes performing a correction procedure of the pseudo-range measurements including applying to the pseudo-range measurements corrections for predictable errors obtaining corrected pseudo-ranges and applying to the corrected pseudo-range measurements a further ionospheric error correction calculation to obtain further ionospheric error correction values.