Navigation Device Road Matching at Small Angle Intersections
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Solution Overview
Problem
Navigation devices face inaccuracies in displaying vehicle position on road maps, particularly at branch points with small angle intersections, due to errors in dead reckoning and GPS positioning, leading to temporary fluctuations in the vehicle position mark, which can confuse users.
Innovation Solution
A navigation device system that includes a vehicle position detection unit, a matching candidate selection unit, a road name determination unit, a weighting unit, and a display control unit to prioritize road candidates with matching road names, weighting coefficients based on distance and direction differences to accurately determine and display the vehicle position on the correct road.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If projection matching is used to select road candidates based on distance and direction, then the vehicle position mark can be displayed on the road map, but the position fluctuates temporarily at small angle intersections causing user confusion
Solution Approach 1:
The system uses feedback from the previously determined road to improve current road selection accuracy. By comparing the currently selected road candidate with the previously determined road, the system adjusts the selection to prevent temporary fluctuations at small angle intersections, ensuring stable and reliable position display.
Solution Approach 2:
The system performs preliminary comparison of road candidates with the previously determined road before final selection. This preliminary action filters out incorrect road candidates that would cause position fluctuations, ensuring that only appropriate roads are selected for displaying the vehicle position mark.
2Device complexity
If dead reckoning is used to detect vehicle position with simple configuration, then the system complexity is reduced, but error accumulates with travel distance reducing accuracy
Solution Approach 1:
The system merges dead reckoning with map matching technology to compensate for the shortcomings of each individual method. Dead reckoning provides continuous position tracking with simple configuration, while map matching corrects accumulated errors by aligning the detected position with actual road geometry, thereby maintaining both simplicity and accuracy.
3Measurement precision
If GPS positioning is used to obtain absolute vehicle position, then measurement precision is improved, but positioning becomes difficult when radio wave conditions degrade due to obstacles
Solution Approach 1:
The system prepares for GPS signal degradation by having dead reckoning as a backup method ready in advance. When GPS positioning becomes difficult due to obstacles such as undulated terrains, tunnels, or tall buildings, the system can switch to or combine with dead reckoning to maintain continuous and accurate position detection, ensuring adaptability to various environments.
4Measurement precision
If map matching is used to align detected vehicle position with road in map data, then position accuracy is improved, but the vehicle position mark may be temporarily shown on wrong road at branch points
Solution Approach 1:
The system uses feedback from the previously determined road to verify current road selection. By comparing the currently selected road candidate with the previously determined road, the system ensures that the vehicle position mark is displayed on the correct road even at branch points, preventing temporary misdisplay while maintaining high position accuracy.
Data Source
AI summary
The present invention provides a navigation device in which the accuracy of placement of a displayed vehicle position mark is improved at an intersection with a small angle. The navigation device weights coefficients of road candidates for consistent matching, in determining the optimal road from a plurality of matching road candidates. Accordingly, a fluctuating display of the vehicle position mark on an incorrect road at an intersection with a small angle is prevented.