1. A navigation system comprising: a positioning system that collects data indicating a position; a computer readable storage medium storing a geographic database comprising altitudinal road geometry data defining straight line segments and vertical curves determined using a Hough Transform having an input of a plurality of altitude data points indicating altitudes at a plurality of locations along roads, wherein the altitudinal road geometry data representing straight line segments and vertical curves determined using the Hough transform have a data size less than a data size of said altitude data points; and a navigation-related application that uses said altitudinal road geometry data to provide a navigation-related feature, wherein said navigation-related feature includes at least one of: a map display, a route calculation, a route guidance, an adaptive cruise control and an adaptive lighting control.