SYSTEM FOR APPLYING CLOTHOID CURVE VALUES TO ROADWAYS IN A GEOGRAPHIC DATA INFORMATION SYSTEM

1 . A system, comprising:

a geographic data information system, wherein the geographic data information system stores database segments in a database, wherein the database segments describe roadways; and

a system for applying clothoid curve values to roadways, wherein the system for applying clothoid curve values to roadways:

determines segment chains from the selected database segments;

prepares the segment chains for transition to curvature space;

transitions 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;

smooths the curvature function;

fits the smoothed curvature function with a more generalized form which remains within a selected tolerance of the smoothed curvature function; and

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

2 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways determines the segment chains, comprising:

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 system of claim 1 , wherein the system for applying clothoid curve values to roadways prepares the segment chains for transition to curvature space, comprising: finding corner interfaces.

4 . The system of claim 3 , wherein finding corner interfaces incorporates shape generalization to remove nearly collinear shape points.

5 . The system 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 system of claim 3 , wherein the system for applying clothoid curve values to roadways prepares the segment chains for transition to curvature space, comprising:

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

7 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways prepares the segment chains for transition to curvature space, comprising:

determination of each segment chain's geographic context.

8 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways smoothes the curvature function, comprising Gaussian smoothing.

9 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways smoothes 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 system 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 system of claim 1 , wherein the system for applying clothoid curve values to roadways fits the smoothed curvature function by seaming together a plurality of weighted least squares regression fit functions into a piecewise linear function.

12 . The system of claim 11 , wherein the system for applying clothoid curve values to roadways fits the smoothed curvature function, further comprising: applying a search for acceptable straight line substitutions to the piecewise linear fit function.

13 . The system 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 system of claim 12 , wherein the system for applying clothoid curve values to roadways fits the smoothed curvature function, further comprising:

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 system of claim 1 , wherein the database segments comprise roadways in x,y positions.

16 . The system of claim 15 , wherein the database segments further comprise non-roadway features.

17 . The system of claim 1 , wherein the database segments comprise roadways in x,y,z positions.

18 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways further comprises:

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

19 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways further comprises:

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

20 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways further comprises:

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

21 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways further comprises:

wherein parameters of curvature are compared with an ideal maneuver.

22 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways further comprises:

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

23 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways further comprises:

approximating roadbed shaping design from shaped geographic line segments.

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

25 . The system of claim 23 , wherein the process for roadbed design approximation consists of determining straight line edge interfaces at the beginning of curve sections.

26 . The system of claim 1 , wherein the system for applying clothoid curve values to roadways further comprises: determining roadbed design parameters from x, y positions and roadbed design principles.