GNSS Integrity Bias Impact Reduction via Statistical Protection Levels

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Solution Overview

Problem

GNSS integrity is compromised by biases in pseudorange measurements, leading to random errors in position solutions and unnecessary limitations in provided integrity.

Innovation Solution

A method is introduced to calculate protection levels by approximating the impact of biases using a normal distribution, rather than relying on the worst-case combination of biases, thereby reducing the bias impact on GNSS integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the worst-case combination of biases is used to calculate protection levels, then safety is ensured, but protection levels become excessively high leading to unnecessary integrity limitations

Engineering Contradiction:

ImprovesafetyVSAvoidprotection level accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the calculation parameter from worst-case bias combination to standard deviation of bias, transforming the protection level calculation from a conservative static approach to a statistically-based dynamic approach that reflects actual error distributions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical worst-case combination approach with a statistical probability model, substituting deterministic bias addition with stochastic error analysis based on normal distribution assumptions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If biases are calculated and combined in the worst-case scenario, then integrity monitoring is conservative, but protection levels increase unnecessarily reducing system availability

Engineering Contradiction:

Improveintegrity monitoringVSAvoidsystem availability

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent changes the integrity monitoring parameter from worst-case bias combination to standard deviation of bias, enabling more realistic protection level calculations that maintain safety while improving system availability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potentially harmful effect of bias uncertainties into a benefit by using statistical distribution characteristics to model bias behavior, transforming conservative overestimation into realistic error bounding

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If standard deviation of bias is used instead of worst-case combination, then protection levels are reduced, but calculation complexity increases

Engineering Contradiction:

Improveprotection level accuracyVSAvoidcalculation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex worst-case combination calculations with simpler standard deviation computations based on normal distribution assumptions, reducing computational burden while improving accuracy

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP3730971B1Reducing bias impact on GNSS integrity

Publication Date: 2025.06.04 HONEYWELL INTERNATIONAL INC

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AI summary

Systems and methods for reducing bias impact on GNSS integrity are described herein. In certain embodiments, a method includes determining a phase of travel of a vehicle. The method also includes determining a probability of hazardously misleading information (PHMI) for the corresponding phase of travel. Further, the method includes determining a protection level (PL) using based on the PHMI, wherein the PL is calculated based on a standard deviation of position error plus a standard deviation of bias along an axis of interest. Additionally, the method includes comparing the protection level against an alert limit.