GNSS Zone Detection Using Dual Polygon Borders
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Solution Overview
Problem
Satellite-based tolling systems face issues with erroneous position estimates due to obstructed sky conditions, leading to false or missed registration of vehicle passages, which reduces user confidence and increases operational costs.
Innovation Solution
The method involves defining a virtual border around a tolling zone using two separate polygons, a smaller inner polygon and a larger outer polygon, with a decision area in between, to improve the accuracy of zone crossing assessments by allowing a distance between the polygons based on known error tolerances and requiring multiple position observations within the inner polygon for valid passage detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single polygon is used to define the tolling zone border, then the system is simple to operate, but the position estimation accuracy deteriorates due to obstructed sky conditions causing erroneous position estimates
Solution Approach 1:
The tolling zone border is segmented into two separate polygons: an inner polygon and an outer polygon. The inner polygon defines the core tolling area while the outer polygon accounts for GNSS position estimation errors. This segmentation allows the system to distinguish between true zone crossings and erroneous position estimates, thereby improving measurement precision without excessive complexity.
Solution Approach 2:
The solution adds a spatial dimension (distance buffer) between the inner and outer polygons to account for measurement uncertainty. By creating a decision area between the two polygons, the system transforms a two-dimensional position estimation problem into a three-dimensional solution space that includes error tolerance margins.
2Reliability
If multiple position observations are required for valid passage detection, then the reliability of zone crossing assessment improves, but the time required for detection increases
Solution Approach 1:
The system performs preliminary actions by continuously monitoring vehicle positions and pre-evaluating potential zone crossings before they occur. By maintaining a buffer zone (decision area) between the inner and outer polygons, the system can prepare for upcoming crossings and reduce the time required for final detection when the vehicle actually crosses the inner polygon boundary.
Solution Approach 2:
The system uses feedback from multiple position observations to confirm zone crossings. By requiring multiple position fixes within the decision area before confirming a crossing, the system filters out false positives while maintaining reasonable detection times through efficient feedback loops that stop evaluating once sufficient confirmations are obtained.
3Reliability
If a distance buffer between polygons is implemented based on error tolerances, then false zone crossing assessments are reduced, but the system complexity increases
Solution Approach 1:
The system changes the geometric parameters of the zone definition by implementing a distance buffer (decision area) between the inner and outer polygons. This parameter change is based on known GNSS error tolerances and systematically reduces false assessments by ensuring that only crossings with sufficient margin are detected, without requiring complex algorithms beyond basic geometric calculations.
Data Source
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AI summary
Method and system for zone based detection of vehicles passing into and out from a geographical zone using polygons to define the border of said zone, wherein a first polygon (32) defines a virtual border against which vehicles passing into the zone is compared by use of a GNSS system (10) comprising an OBU in every vehicle to be surveyed by the method. A second polygon (31) larger than the first polygon (32) and completely enveloping said first polygon is defined as a virtual border against which objects passing out from the zone is compared by use of the GNSS system.