Data processing: vehicles – navigation – and relative location – Navigation – Determination of travel data based on the start point and...
Reexamination Certificate
1999-05-13
2001-09-04
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Determination of travel data based on the start point and...
C701S204000, C701S208000, C340S994000
Reexamination Certificate
active
06285950
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a vehicle navigation system, and more particularly, to a vehicle navigation system having a function to calculate a travel time to a destination.
Such a navigation system has two main and interrelated functions: the first function is to display to the user a map of the present vehicle location; and the second function is to provide guidance on a guided route from a starting point to a destination. The second function is generally referred to as route guidance or selection. A route is typically optimized for one of various parameters, for instance, minimum travel time, minimum travel distance, maximum use of freeway, or other parameters pertaining to movement of a vehicle on a road network.
Another function of such a navigation system relating to the above two main functions is a function to calculate and display a travel time to a destination. Usually, a navigation system has map data and searches the data to determine an optimum route. The map data include travel times of all the road segments in an area encompassing a starting point and a destination point. These travel times are obtained, for example, by actually driving those road segments under various road conditions and averaging the actual travel times. The travel times may also be obtained, without actually traveling the road segments, by predicting travel speeds based on the road characteristics of the segments, such as a road width, road type, etc. The predicted travel speeds may be adjusted according to posted speed limits.
Conventionally, a travel time to a destination is calculated by adding these travel times in the map data along the road segments that are yet to be traveled along the optimum route. The problem with this conventional method of estimating a travel time to a destination is that the estimated travel time necessarily includes an error because the travel times in the map data do not accurately reflect the particular driving conditions to which the vehicle is actually subjected.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a vehicle navigation system having an improved function to estimate a travel time to a destination. According to the present invention, estimation of a travel time to a destination includes two steps of calculation. First, a travel time to reach an intermediate point forward of the present vehicle position is calculated based on a current average speed. Second, a travel time to reach the destination from the intermediate point is calculated based on link costs. A travel time to reach the destination from the present vehicle position is a sum of the travel times obtained by the first calculation and the second calculation.
The intermediate point may be a next maneuver point or a point between the next maneuver point and the present vehicle position, or may be a point beyond the next maneuver point. At the first step, a travel time to reach the intermediate point is calculated by dividing a distance between the intermediate point and the present vehicle position by the current average speed. At the second step, using the conventional method, a travel time to reach the destination from the intermediate point is calculated by adding the link costs of the road segments between those two points.
Since the current average speed reflects the road conditions to which the vehicle is actually subjected, the travel time obtained by the first calculation should be more accurate than a travel time that could be calculated by adding the link costs between the intermediate point and the present vehicle point. As a result, a sum of the travel times obtained by the first calculation and the second calculation should be more accurate than a travel time that could be calculated by adding the link costs throughout the road segments that are yet to be traveled up to the destination.
REFERENCES:
patent: 4153874 (1979-05-01), Kaestner
patent: 4371935 (1983-02-01), Yamaki
patent: 5243529 (1993-09-01), Kashiwazaki
patent: 5365449 (1994-11-01), Kashiwazaki
patent: 5371678 (1994-12-01), Nomura
patent: 5541845 (1996-07-01), Klein
patent: 5568390 (1996-10-01), Hirota et al.
patent: 5689252 (1997-11-01), Ayanoglu et al.
patent: 5724243 (1998-03-01), Westerlarge et al.
patent: 5787383 (1998-07-01), Moroto et al.
patent: 5928308 (1999-07-01), Nanba et al.
Alpine Electronics Inc.
Brinks Hofer Gilson & Lione
Nguyen Tan
LandOfFree
Vehicle navigation system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vehicle navigation system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vehicle navigation system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2468312