Abstract: A method detects a particular freeway-ramp-freeway situation in a calculated route and corrects the route by replacing the freeway-ramp-freeway situation with all-freeway segments. The method includes the steps of: establishing a calculated route to a destination; examining the calculated route to detect whether there is a first point where the calculated route exits a freeway and a second point where the calculated route enters a freeway; evaluating map data to determine whether the freeway exited and the freeway entered are the same freeway; and replacing road segments of the calculated route between the first point and the second point constituting the freeway-ramp-freeway situation with freeway segments between the first point and the second point, thereby avoiding the freeway-ramp-freeway situation.

Abstract: A distance adjustment method and apparatus for a navigation system produces a maneuver instruction for an intersection at the most appropriate timing and location during the route guidance. The method includes the steps of: searching an upcoming intersection on the calculated route that requires the user to make a turn therein; retrieving data concerning the upcoming intersection from a map database; adjusting a final distance from a reference point of the intersection by evaluating the retrieved data concerning the intersection; and generating a maneuver instruction at a timing when the user has reached the adjusted final distance from the reference point of the intersection, thereby notifying the user to make a turning maneuver at the intersection.

Abstract: A method and apparatus for a navigation system for calculating a route to an intersection destination establishes an optimum route to the intersection. The method and apparatus creates a virtual zero-length dummy link, connects one end of the virtual zero-length dummy link to all link-spot pairs indicating an original intersection destination, sets another end of the virtual zero-length dummy link as a temporary destination, calculates possible routes between the temporary destination and a current vehicle position and selects the optimum route. After determining the optimum route, the navigation system removes the virtual zero-length dummy link and starts the route guidance operation to the intersection destination.

Abstract: A distance adjustment method and apparatus for a navigation system produces a maneuver instruction for an intersection at the most appropriate timing and location during the route guidance. The method includes the steps of: searching an upcoming intersection on the calculated route that requires the user to make a turn therein; retrieving data concerning the upcoming intersection from a map database; adjusting a final distance from a reference point of the intersection by evaluating the retrieved data concerning the intersection; and generating a maneuver instruction at a timing when the user has reached the adjusted final distance from the reference point of the intersection, thereby notifying the user to make a turning maneuver at the intersection.

Abstract: A method and apparatus for link promotion for a navigation system allows expansion of search in a lower layer to determine an optimum climbing point to an upper layer to search an optimum route. The link promotion procedure includes the steps of determining whether an upper link exists for a lower link, setting the upper link as a promoted link if such an upper link exists even if a climbing node point does not exist that connect the lower link and the upper link, and comparing a candidate normal route and a promoted route to find an optimum route.

Abstract: A system for comparing various routes, identifying delays among the routes, and selecting a more desirable route, even if the desirable route is not the shortest distance, is described. In one embodiment, the more desirable route is the faster route. In one embodiment, the more desirable route is a route with fewer in-route delays. In one embodiment, the system loads a map from a memory and retrieves road level information based on position information of roads and delays. The roads in the map are described at various levels of detail, wherein lower levels contain more detail and relatively higher levels that contain less detail. One embodiment includes detecting a route having links with a substantially larger number of delays and adding an additional penalty cost for the links at higher levels based on penalties computed from the links at lower level road levels.

Abstract: A navigation system is able to find an optimum route to a destination even when a large non-digitized area exists between a starting point to the destination. The navigation system produces processing points based on a particular shape and size of the large non-digitized area and determines whether such processing points should be used for route search operations. When it is determined that the route search operation is effective, the navigation system performs A* algorithm search operations with respect to the start point, processing points and the destination and detects an optimum route to detour the large non-digitized area.

Abstract: A method and apparatus for link promotion for a navigation system allows expansion of search in a lower layer to determine an optimum climbing point to an upper layer to search an optimum route. The link promotion procedure includes the steps of determining whether an upper link exists for a lower link, setting the upper link as a promoted link if such an upper link exists even if a climbing node point does not exist that connect the lower link and the upper link, and comparing a candidate normal route and a promoted route to find an optimum route.

Abstract: A method detects a particular freeway-ramp-freeway situation in a calculated route and corrects the route by replacing the freeway-ramp-freeway situation with all-freeway segments. The method includes the steps of: establishing a calculated route to a destination; examining the calculated route to detect whether there is a first point where the calculated route exits a freeway and a second point where the calculated route enters a freeway; evaluating map data to determine whether the freeway exited and the freeway entered are the same freeway; and replacing road segments of the calculated route between the first point and the second point constituting the freeway-ramp-freeway situation with freeway segments between the first point and the second point, thereby avoiding the freeway-ramp-freeway situation.

Abstract: A system for comparing various routes, identifying delays among the routes, and selecting a more desirable route, even if the desirable route is not the shortest distance, is described. In one embodiment, the more desirable route is the faster route. In one embodiment, the more desirable route is a route with fewer in-route delays. In one embodiment, the system loads a map from a memory and retrieves road level information based on position information of roads and delays. The roads in the map are described at various levels of detail, wherein lower levels contain more detail and relatively higher levels that contain less detail. One embodiment includes detecting a route having links with a substantially larger number of delays and adding an additional penalty cost for the links at higher levels based on penalties computed from the links at lower level road levels.

Abstract: A method and apparatus for a navigation system for calculating a route to an intersection destination establishes an optimum route to the intersection. The method and apparatus creates a virtual zero-length dummy link, connects one end of the virtual zero-length dummy link to all link-spot pairs indicating an original intersection destination, sets another end of the virtual zero-length dummy link as a temporary destination, calculates possible routes between the temporary destination and a current vehicle position and selects the optimum route. After determining the optimum route, the navigation system removes the virtual zero-length dummy link and starts the route guidance operation to the intersection destination.

Abstract: A distance adjustment method and apparatus for a navigation system produces a maneuver instruction for an intersection at the most appropriate timing and location during the route guidance. The method includes the steps of: searching an upcoming intersection on the calculated route that requires the user to make a turn therein; retrieving data concerning the upcoming intersection from a map database; adjusting a final distance from a reference point of the intersection by evaluating the retrieved data concerning the intersection; and generating a maneuver instruction at a timing when the user has reached the adjusted final distance from the reference point of the intersection, thereby notifying the user to make a turning maneuver at the intersection.

Abstract: An off-route recalculation method and apparatus for a navigation system calculates a new route when a vehicle is deviated from an originally calculated route to a destination. The method is comprised of the steps of: detecting whether a user vehicle has deviated from an originally calculated route; predicting a path that a user is likely to take until a new route to the destination is calculated; calculating a predicted distance that the user vehicle advances through the predicted path during a time the new route to the destination is calculated and during a turn prepare time, thereby determining a start position of the new route; calculating the new route to the destination incorporating the start position.

Abstract: An off-route recalculation method and apparatus for a navigation system calculates a new route when a vehicle is deviated from an originally calculated route to a destination. The method is comprised of the steps of: detecting whether a user vehicle has deviated from an originally calculated route; predicting a path that a user is likely to take until a new route to the destination is calculated; calculating a predicted distance that the user vehicle advances through the predicted path during a time the new route to the destination is calculated and during a turn prepare time, thereby determining a start position of the new route; calculating the new route to the destination incorporating the start position.

Abstract: A navigation system is able to find an optimum route to a destination even when a large non-digitized area exists between a starting point to the destination. The navigation system produces processing points based on a particular shape and size of the large non-digitized area and determines whether such processing points should be used for route search operations. When it is determined that the route search operation is effective, the navigation system performs A* algorithm search operations with respect to the start point, processing points and the destination and detects an optimum route to detour the large non-digitized area.