Navigation apparatus and method for exploring an optimal route based on characteristics of an exploration object zone
First Claim
1. A route exploration method for exploring an optimal route that links a departure point and a destination, comprising the steps of:
- determining a characteristic of an exploration object zone;
selecting one of at least two exploration techniques depending on the determined characteristic; and
identifying the optimal route between the departure point and the destination using the selected one of said at least two exploration techniques.
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Abstract
A method and apparatus for reliably determining an optimal route between a departure point and a destination in an exploration object zone, the optimal route being determined according to the situation of roads separating the departure point and the destination. Prior to route exploration, an area determiner counts the total number of intersection network lists associated with a route exploration object zone, which lists are stored in a route exploration memory. When a density of intersections (which is the total number of intersection network lists divided by the size of the route exploration object zone) exceeds a certain value, the area determiner determines that the object zone lies in an urban (high road density) district. When the density of intersections is smaller, the area determiner determines that the object zone lies in a suburban (low road density) district. When the area determiner determines that the object zone lies in an urban district, an optimal route explorer executes heuristic exploration; that is, it uses intersection network lists to explore an optimal route linking a departure point and a destination while trimming away routes that deviate from the direction specified with a straight line joining the departure point and destination or while lowering the priorities of such routes. When the area determiner determines that the object zone lies in a suburban district, the optimal route explorer executes normal non-heuristic (exhaustive) exploration.
72 Citations
20 Claims
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1. A route exploration method for exploring an optimal route that links a departure point and a destination, comprising the steps of:
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determining a characteristic of an exploration object zone; selecting one of at least two exploration techniques depending on the determined characteristic; and identifying the optimal route between the departure point and the destination using the selected one of said at least two exploration techniques. - View Dependent Claims (2)
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3. A route exploration method in which road data including intersection network lists is referenced to explore an optimal route linking a departure point and a destination, comprising the steps of:
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referencing said road data to determine a road density of an exploration object zone; when said exploration object zone lies in a high road density district, executing a heuristic exploration whereby routes deviating from the direction specified with a straight line joining the departure point and destination are trimmed away or the priorities of such routes are lowered; and when said exploration object zone lies in a low road density district, executing a non-heuristic exploration. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A route exploration method for a navigation apparatus including a vehicle location detector and a guidance route memory from which road data including intersection network lists is referenced to explore an optimal route linking a departure point and a destination, comprising the steps of:
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reading a road data portion from the guidance route memory; calculating a density of intersections in the road data portion by dividing the total number of intersections corresponding to the total number of intersection network lists by the size of an object area for which intersection network lists are created, and then comparing with a certain reference value; when the calculated density exceeds said reference value, determining that an exploration object zone lies in an urban district; when the calculated density is less than said reference value, determining that an exploration object zone lies in a suburban district; when the determination is that the exploration object zone lies in an urban district, reading the latitudinal and longitudinal coordinates of the i-th intersection (i=1, 2, etc., and n) and a certain intersection adjoining the i-th intersection from an intersection network list and a vehicle location from the vehicle location detector, and calculating an azimuth of a route leading from the vehicle location to the adjacent intersection from the i-th intersection; checking if said azimuth is deviating by more than a specified angle from the azimuth of the destination relative to the departure; when said azimuth is deviating by more than the specified angle, trimming away the route whereby exploration will not proceed with the route any longer; and when said exploration object zone lies in a suburban district, executing non-heuristic exploration.
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20. A vehicular navigation apparatus having a memory that stores map data including road data, a vehicle location detector for detecting a current location of a vehicle, a guidance route memory that stores guidance route data concerning routes leading to a desired destination, and a map display controller that uses map data stored in said map data memory and guidance route data stored in said guidance route memory to display a map image, which shows a location of the vehicle and its surrounding areas, together with a vehicle location mark and a guidance route as a route guidance screen, and comprising:
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an operation unit designating route guidance that provides a desired route leading to the destination; and an area determiner that when said operation unit is used to designate route guidance, references road data to determine whether an exploration object zone lies in an high or low density district;
wherein;when said area determiner determines that said exploration object zone lies in a high road density district, a heuristic exploration trims away routes deviating from the direction specified with a straight line joining the departure point and destination or the priorities of such routes are lowered; and when said exploration object zone lies in a low road density district, a non-heuristic exploration is executed.
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Specification