Patent ID: 8332151

Claim:
A gradient information calculating system, comprising: a first calculating unit that detects three-dimensional location information through autonomous navigation, and calculates a first gradient value of a given point on a road, based on a distance traveled in a given period of time, and an on-plane distance obtained by projecting the distance traveled on a horizontal plane; a road map information storing unit that stores road map information that represents each road by a first node and a second node of which the location information is known, and a link that connects the first node with the second node; a second calculating unit that estimates an elevation of each of the nodes from previously measured elevation data, and calculates a second gradient value for the link, based on a difference in elevation between the first node and the second node, and the length of the link; and a gradient data selecting unit that compares the first gradient value with the second gradient value, and selects one of the first and second gradient values to be adopted as a gradient value of the given point or link, according to a difference between the first gradient value and the second gradient value.