GNSS Contour Table Height Aiding for Urban Positioning
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Solution Overview
Problem
GPS receivers face challenges in accurately calculating position and velocity in degraded signal environments, such as urban areas with tall buildings, where satellite signals are obstructed, leading to inaccurate navigation data.
Innovation Solution
A contour table is maintained within the GNSS chipset containing height attributes for selected areas, which provides height information to improve navigation solutions by interpolating data for specific locations, reducing storage needs and enhancing accuracy in urban environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS receiver uses traditional positioning algorithms in degraded signal environments, then position calculation can be performed, but position accuracy deteriorates due to satellite signal obstruction
Solution Approach 1:
The system pre-acquires and stores elevation data from contour tables before GPS signal degradation occurs. When satellite signals are obstructed in urban canyons or tunnels, the receiver retrieves previously stored elevation information to aid position calculation, eliminating the need for real-time signal processing during degraded conditions.
Solution Approach 2:
Elevation data from contour tables serves as an intermediary parameter that bridges the gap between limited satellite measurements and accurate position determination. The receiver uses this external elevation information as additional constraints in the positioning algorithm, enabling accurate 3D position calculation even with reduced satellite visibility.
2Measurement precision
If extensive map databases are used to provide real-time position display and turn-by-turn directions, then navigation accuracy improves, but memory space requirements increase significantly
Solution Approach 1:
The system extracts only the essential elevation data from complete map databases and stores it in compact contour tables. By selecting and storing only the critical height information needed for positioning aid rather than full map details, the system achieves navigation accuracy improvement with minimal memory consumption.
Solution Approach 2:
The contour tables store elevation information selectively for specific geographic locations where GPS signal degradation is most likely to occur, such as urban areas with tall buildings. This localized storage approach provides navigation accuracy improvements precisely where needed while minimizing overall memory requirements.
Data Source
AI summary
The present invention is related to location positioning systems, and more particularly, to a method and apparatus for making accuracy improvements to a GPS receiver's navigation calculations. According to a first aspect, the invention includes maintaining a table of height attributes for major cities and urban areas around the world (contour table) in the GNSS chipset. The information in the table preferably includes latitude, longitude of the city along with height attributes of those cities, such as the average, min, max height and region boundary etc. Additional information such as average gradient could also be saved in the table. According to further aspects, when GPS signals are degraded in environments such as urban canyons, the height information can be obtained from the table and used to improve the navigation solution.