COMPUTER READABLE STORAGE MEDIUM STORING INSTRUCTIONS FOR APPLYING CLOTHOID CURVE VALUES TO ROADWAYS IN A GEOGRAPHIC DATA INFORMATION SYSTEM

1 . A computer readable storage medium, storing instructions executable by a processor for applying clothoid curve values to roadways in a geographic data information system, the instructions comprising:

selecting database segments in the geographic data information system, wherein the database segments describe roadways;

determining segment chains from the selected database segments;

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 the identified segments of straight lines, transition zones, and segments of constant curvature in the geographic data information system.

2 . The computer readable storage medium of claim 1 , 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 important location, and touch no other important location, until reaching the same or other important location.

3 . The computer readable storage medium of claim 1 , wherein preparing the segment chains for transition to curvature space further comprises finding corner interfaces.

4 . The computer readable storage medium of claim 3 , wherein finding corner interfaces incorporates shape generalization to remove nearly collinear shape points.

5 . The computer readable storage medium of claim 3 , wherein finding corner interfaces comprises:

using relative accuracy information to approximate a line attached to a curve defined by three successive shape points.

6 . The computer readable storage medium of claim 3 , wherein preparing the segment chains for transition to curvature space further comprises:

generalization of shape points that have not been identified as part of a corner interface.

7 . The computer readable storage medium of claim 1 , wherein preparing the segment chains for transition to curvature space comprises:

determination of each segment chain's geographic context.

8 . The computer readable storage medium of claim 1 , wherein smoothing the curvature function comprises Gaussian smoothing.

9 . The computer readable storage medium of claim 1 , wherein smoothing the curvature function comprises:

an approximation to Gaussian smoothing with a piecewise linear function connecting Gaussian sample points placed at intervals from shape points.

10 . The computer readable storage medium of claim 9 , wherein the approximation to Gaussian smoothing is obtained from iterative samples stored in a table that associates Gaussian intervals with numeric parameters.

11 . The computer readable storage medium of claim 1 , wherein fitting the smoothed curvature function is performed by seaming together a plurality of weighted least squares regression fit functions into a piecewise linear function.

12 . The computer readable storage medium of claim 11 , wherein fitting the smoothed curvature function further comprises:

applying a search for acceptable straight line substitutions to the piecewise linear fit function.

13 . The computer readable storage medium of claim 12 , wherein the search for acceptable straight line substitutions to the piecewise linear fit function further comprises:

generating a straight line function value that generates no change in overall function area

14 . The computer readable storage medium of claim 12 , wherein fitting the smoothed curvature function further comprises:

applying a search for straight lines and singular points in the piecewise linear fit function which can be acceptably replaced with a value of zero.

15 . The computer readable storage medium of claim 1 , wherein the database segments comprise roadways in x,y positions.

16 . The computer readable storage medium of claim 15 , wherein the database segments further comprise non-roadway features.

17 . The computer readable storage medium of claim 1 , wherein the database segments comprise roadways in x,y,z positions.

18 . The computer readable storage medium of claim 1 , further comprising:

resulting in parameters of curvature gradients as clothoids mapped to transition zones.

19 . The computer readable storage medium of claim 1 , further comprising:

resulting in parameters of curvature mapped into segments of constant curvature.

20 . The computer readable storage medium of claim 1 , further comprising:

wherein parameters of curvature are used to compute safe speed parameters.

21 . The computer readable storage medium of claim 1 , further comprising:

wherein parameters of curvature are compared with an ideal maneuver.

22 . The computer readable storage medium of claim 1 , further comprising:

scoring a driver's performance relative to an optimum driving technique.

23 . The computer readable storage medium of claim 1 , further comprising:

approximating roadbed shaping design from shaped geographic line segments.

24 . The computer readable storage medium of claim 23 , wherein the roadbed design is composed of straight lines, circular arcs, and clothoidal sections.

25 . The computer readable storage medium of claim 23 , wherein the process for roadbed design approximation consists of a first step of determining straight line edge interfaces at the beginning of curve sections.

26 . The computer readable storage medium of claim 1 , further comprising:

determining roadbed design parameters from x, y positions and roadbed design principles.