Patent ID: 7912879

Claim:
A method for applying clothoid curve values to roadways in a geographic data information system, comprising: selecting database segments in the geographic data information system, wherein the database segments describe roadways; determining segment chains from the selected database segments, wherein determining the segment chains comprises: identifying a plurality of at grade junctions of the selected segments and all dead ends of the selected segments as important locations; and finding each geographic chain of segments that traverse from any such important location, and touch no other such important location, until reaching the same or other such important location; preparing the segment chains for transition to curvature space; transitioning to a curvature function in the curvature space, by computing heading change at points along the segment chains, resulting in a transformation of the segment chains into clothoids; smoothing the curvature function; fitting the smoothed curvature function with a more generalized form which remains within a selected tolerance of the smoothed curvature function; and storing parametric values of the smoothed curvature function for the segment chains in the geographic data information system; wherein the more generalized form of the smoothed curvature function is obtained by recursively applying a regression technique to said smoothed curvature function and seaming together the resulting plurality of regression-fit functions into a piecewise linear function, said seaming being achieved by assigning a common value to the more generalized form of the smoothed curvature function at the point where successive regression-fit functions are seamed together.