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A navigation system having a central device which uses a link shape compression unit to compress information of altitude changes of a road link obtained from a three-dimensional road map, and calculates a geometry parameter based on variation of energy of a vehicle travelling on the road link. An on

A navigation system having a central device which uses a link shape compression unit to compress information of altitude changes of a road link obtained from a three-dimensional road map, and calculates a geometry parameter based on variation of energy of a vehicle travelling on the road link. An on-board terminal device estimates the vehicle's average travelling pattern by using a travel-pattern-estimation unit based on the geometry parameter calculated by the central device, a link-travelling time estimated from statistically-stored traffic information, and a link length. The on-board terminal device further calculates fuel consumption of the vehicle travelling on each road link based on the estimated travelling pattern and parameters of the vehicle by using a fuel-consumption calculation unit, and then, searches a fuel-efficient route by using the fuel consumption as a link cost. The on-board terminal device has a vehicle-type selector for selecting a type of the vehicle.

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1. A navigation system for searching a route to a destination and guiding a vehicle to the destination, the navigation system comprising: a road map data storage unit storing road map data including altitude information;an energy variation calculation unit programmed to calculate a variation of mech

1. A navigation system for searching a route to a destination and guiding a vehicle to the destination, the navigation system comprising: a road map data storage unit storing road map data including altitude information;an energy variation calculation unit programmed to calculate a variation of mechanical energy of the vehicle travelling on a road link included in the road map data; anda route-search unit programmed to search for a fuel-efficient route for the vehicle based on the variation of mechanical energy calculated by the energy variation calculation unit;a display unit programmed to display the fuel-efficient route for the vehicle;wherein the energy variation calculation unit is further programmed to:divide the road link to be used for route-searching into a plurality of sub-links each approximated by a line segment;calculate the variation of mechanical energy of the vehicle travelling on the plurality of the sub-links in an acceleration travel mode, a deceleration travel mode, and a constant-speed travel mode, wherein each of the variations of mechanical energy includes a total variation of friction energy based on a length of each sub-link calculated from coordinate information, potential energy based on an altitude difference of both ends of each sub-link calculated by the coordinate information including the altitude information, and kinetic energy;categorize the sub-links in accordance with an estimated fuel consumption in each of the acceleration travel mode, the deceleration travel mode, and the constant-speed travel mode into a first category in which the estimated fuel consumption is equal to a minimum fuel consumption of the vehicle in all of the acceleration, deceleration and constant-speed travel modes, a second category in which the estimated fuel consumption is not equal to the minimum fuel consumption in the acceleration travel mode but is equal to the minimum fuel consumption in the deceleration and constant-speed travel modes, a third category in which the estimated fuel consumption is not equal to the minimum fuel consumption in the acceleration and constant-speed travel modes but is equal to the minimum fuel consumption in the deceleration travel mode, or a fourth category in which the estimated fuel consumption is not equal to the minimum fuel consumption in all of the acceleration, deceleration and constant-speed travel modes;calculate a sum of the variations, per each categorized sub-link, of mechanical energy that is the total variation of friction energy, potential energy, and kinetic energy of the vehicle travelling on the plurality of sub-links of the road link; andrender the sum calculated per each categorized sub-link as a geometry parameter of the road link and stores the geometry parameter in a geometry parameter storage unit;wherein the route-search unit is programmed to use the geometry parameters in searching for the fuel-efficient route. 2. The navigation system as claimed in claim 1, further comprising: a link-travelling time-calculating unit programmed to obtain a link-travelling time of the road link, andan input unit programmed to receive vehicle information which indicates a type of the vehicle,wherein the energy variation calculation unit is further programmed to:obtain the link-travelling time of the road link from the link-travelling time-calculating unit;estimate an acceleration-travel pattern, a deceleration-travel pattern, and a constant-speed-travel pattern of the vehicle travelling the road link based on the link-travelling time of the road link obtained by the link-travelling time-calculating unit and length of the road link obtained from the road map data storage unit; andestimate fuel consumption of the vehicle travelling the road link based on the estimated travel patterns of the vehicle and the geometry parameter;wherein the route-search unit is further programmed to:receive vehicle information which indicates the type of the vehicle from the input unit; andestimate the fuel consumption of the vehicle, the type of which is inputted into the input unit. 3. A navigation method using a navigation system having a road map data storage unit having road map data including altitude information, the navigation method comprising the steps, carried out by the navigation system for searching a route and guiding a vehicle to a destination, of: (a) calculating a variation of mechanical energy of the vehicle travelling on a road link included in the road map data;(b) searching for a fuel-efficient route for the vehicle based on the calculated variation of mechanical energy; and(c) displaying the fuel-efficient route on a display unit;wherein step (a) comprises:(i) dividing the road link to be used for route-searching into a plurality of sub-links each approximated by a line segment;(ii) calculating the variation of mechanical energy of the vehicle travelling on the plurality of sub-links in each of an acceleration travel mode, a deceleration travel mode, and a constant-speed travel mode, wherein each of the variations of mechanical energy includes a total variation of friction energy based on lengths of the plurality of sub-links calculated from coordinate information, potential energy based on an altitude difference of both ends of each sub-link calculated from the coordinate information including the altitude information, and kinetic energy;(iii) categorizing the sub-links in accordance with an estimated fuel consumption in each of the acceleration travel mode, the deceleration travel mode, and the constant-speed travel mode intoa first category in which the estimated fuel consumption is equal to a minimum fuel consumption of the vehicle in all of the acceleration, deceleration and constant-speed travel modes,a second category in which the estimated fuel consumption is not equal to the minimum fuel consumption in the acceleration travel mode, but is equal to the minimum fuel consumption in the deceleration and constant-speed travel modes,a third category in which the estimated fuel consumption is not equal to the minimum fuel consumption in the acceleration and constant-speed travel modes, but is equal to the minimum fuel consumption in the deceleration travel mode, ora fourth category in which the estimated fuel consumption is not equal to the minimum fuel consumption in all of the acceleration, deceleration and constant-speed travel modes;(iv) calculating a sum of the variations, per each categorized sub-link, of mechanical energy that is the total variation of friction energy, potential energy, and kinetic energy of the vehicle travelling the plurality of sub-links of the road link; and(v) rendering the sum calculated per each categorized sub-link as a geometry parameter of the road link and stores the geometry parameter in a geometry parameter storage unit; andwherein step (b) comprises:(i) using the geometry parameters in searching for the fuel-efficient route. 4. The navigation method as claimed in claim 3, further comprising the steps of: obtaining a link-travelling time of the road link;estimating an acceleration-travel pattern, a deceleration-travel pattern, and a constant-speed-travel pattern of the vehicle travelling the road link based on the obtained link-travelling time of the road link and length of the road link obtained from the road map data storage unit when searching a route for guiding the vehicle to the destination;estimating fuel consumption of the vehicle travelling the road link based on the estimated travel patterns of the vehicle and the geometry parameter;inputting vehicle information which indicates type of the vehicle into an input unit of the navigation system; andestimating the fuel consumption of the vehicle, of which type is inputted into the input unit, when searching a route for guiding the vehicle to the destination. 5. A navigation system comprising: a road map data storage unit storing road map data therein;an energy variation calculation unit programmed to: calculate the variation of energy of the vehicle travelling on each road link included in the road map data based on the data of the variation of energy according to each travel pattern of the vehicle,calculate a sum of the variations, per each of a plurality of categorized sub-links, of mechanical energy that is the total variation of friction energy, potential energy, and kinetic energy of the vehicle travelling on the plurality of sub-links of the road link, andrender the sum calculated per each categorized sub-link as a geometry parameter of the road link;a geometry parameter storage unit programmed to store data of variations of energy previously calculated for road links included in the road map data by using altitude information, the data of variations of energy being stored as geometry parameters;a route-search unit programmed to search for a fuel-efficient route for the vehicle based on the variation of energy calculated by the energy variation calculation unit; anda display unit programmed to display the fuel-efficient route for the vehiclewherein the geometry parameter storage unit stores the sum of variations, per each categorized sub-link, of mechanical energy that is a total variation of friction energy, potential energy, and kinetic energy of the vehicle travelling sub-links of the road link as the geometry parameter of the road link, the sub-links being categorized in accordance with an estimated fuel consumption in each of an acceleration travel mode, a deceleration travel mode, and the constant-speed travel mode into:a first category in which the estimated fuel consumption is equal to a minimum fuel consumption of the vehicle in all of the acceleration, deceleration and constant-speed travel modes,a second category in which estimated fuel consumption is not equal to the minimum fuel consumption in the acceleration travel mode, but is equal to the minimum fuel consumption in the deceleration and constant-speed travel modes,a third category in which estimated fuel consumption is not equal to the minimum fuel consumption in the acceleration and constant-speed travel modes, but is equal to the minimum fuel consumption in the deceleration travel mode, ora fourth category in which estimated fuel consumption is not equal to the minimum fuel consumption in all of the acceleration, deceleration and constant-speed travel modes,wherein each sub-link is approximated by a line segment. 6. The navigation system as claimed in claim 5, further comprising: a link-travelling time-calculating unit programmed to obtain a link-travelling time of the road link, andan input unit programmed to receive vehicle information which indicates a type of the vehicle,wherein the energy variation calculation unit is further programmed to:obtain a link-travelling time of the road link from the link-travelling time-calculating unit;estimate an acceleration-travel pattern, a deceleration-travel pattern, and a constant-speed-travel pattern of the vehicle travelling the road link based on the obtained link-travelling time of the road link and length of the road link obtained from the road map data storage unit; andestimate fuel consumption of the vehicle travelling the road link based on the estimated travel patterns of the vehicle and the geometry parameterwherein the route-search unit is further programmed to:receive vehicle information which indicates a type of the vehicle from the input unit; andestimate the fuel consumption of the vehicle of which type is inputted into the input unit.