Data processing: vehicles – navigation – and relative location – Navigation
Reexamination Certificate
2000-04-14
2001-10-16
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
C701S208000
Reexamination Certificate
active
06304818
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application relates to and incorporates herein by reference Japanese Patent Application No. 11-132867 filed on May 13, 1999.
BACKGROUND OF THE INVENTION
The present invention relates to a vehicular navigation system which retrieves coordinate points of road configurations included in road map data stored in a memory device, determines road curves and informs the determined road curves.
JP-A-9-189565 discloses a conventional vehicular navigation system. This system uses three successive coordinate points indicating a road configuration or shape to calculate a radius of a circle which passes through these coordinate points and a radius of curvature of a subject road curve. The presence and absence of the curve is determined based on the calculated radius of curvature. The system informs a vehicle driver by a visual display or vocal announcement of the position (point) of the curve together with its radius of curvature or length of the curve as well as an angle of curving.
A memory device such as CD-ROMs or the like which store the road map data and the like has a limited memory or storage capacity. Therefore, the memory device is incapable of storing a plenty of data of coordinate points indicative of road configuration to the extent sufficient to determine curves accurately. Thus, it is likely that the curve is determined only roughly or erroneously.
SUMMARY OF THE INVENTION
The present invention therefore has an object of providing a vehicular navigation system capable of determining road curves with high accuracy.
According to the present invention, four or more successive road coordinate points representing a road configuration are retrieved from a road map data. The road coordinate points are interpolated to have more coordinate points by using a B-spline function based on the retrieved road coordinate points. A radius of curvature is calculated with respect to each of the interpolated coordinate point. A road curve and direction thereof are detected based on the calculated radii of curvature.
REFERENCES:
patent: 5661650 (1997-08-01), Sekine et al.
patent: 5978731 (1999-01-01), Matsuda
patent: 6058350 (2000-05-01), Ihara
patent: 6067497 (2000-05-01), Sekine et al.
patent: 6138084 (2000-10-01), Mine
patent: 6141619 (2000-10-01), Sekine
patent: 9-189565 (1997-07-01), None
Denso Corporation
Law Office of David G. Posz
Nguyen Tan
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