Application of the ψ-s curve to road geometry extraction and modeling
First Claim
1. A method of determining straight line segments, circular arcs and clothoidal arcs that form a complex curve comprising:
- providing data indicating a shape of the complex curve along a length thereof;
forming a transform of the shape by determining an angle made with a fixed line by a tangent to the shape along the length thereof to provide a plurality of tangent angles;
forming a plot of the tangent angles along the length of the complex curve against the length along the complex curve;
determining straight lines that fit said plot;
using said straight lines that fit said plot to determine at least one of the line segments and circular arcs that form the shape of the complex curve along the length thereof; and
representing said complex curve in a geographic database by storing, in said geographic database, data that indicate the at least one of the line segments and circular arcs that form the shape of the complex curve along the length thereof.
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Accused Products
Abstract
A method for determining the line segments, circular arcs, and clothoidal arcs that form a complex curve along a length thereof is disclosed. A ψ-s curve of the complex curve is determined, which is a plot of tangent angles, wherein the angle is made with a fixed line by a tangent to the complex curve along the length thereof. The straight line portions and parabolic portions of the plot of the ψ-s curve are determined and used to determine the corresponding circular arcs and straight lines that form the complex curve and clothoidal arcs that form the complex curve, respectively. The ψ-s curve can be used to identify the curves and straight lines that define the geometry of roads and therefore can be used to store data that indicate the geometry of roads in a geographic database that contains data representing the roads.
43 Citations
27 Claims
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1. A method of determining straight line segments, circular arcs and clothoidal arcs that form a complex curve comprising:
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providing data indicating a shape of the complex curve along a length thereof; forming a transform of the shape by determining an angle made with a fixed line by a tangent to the shape along the length thereof to provide a plurality of tangent angles; forming a plot of the tangent angles along the length of the complex curve against the length along the complex curve; determining straight lines that fit said plot; using said straight lines that fit said plot to determine at least one of the line segments and circular arcs that form the shape of the complex curve along the length thereof; and representing said complex curve in a geographic database by storing, in said geographic database, data that indicate the at least one of the line segments and circular arcs that form the shape of the complex curve along the length thereof. - View Dependent Claims (2, 3)
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4. A method of representing geometry of a road segment in a geographic database comprising:
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providing data indicating a shape of the road segment along a length thereof; forming a transform of the shape by determining an angle made with a fixed line by a tangent to the shape at each point along the length to provide a plurality of tangent angles; forming a plot of the tangent angles at each point along the length of the road segment against the length along the road segment; determining straight lines that correspond to said plot; using the straight lines that correspond to the plot to determine at least one of line segments and circular arcs that form the shape of the road segment along the length thereof; and representing said road segment in the geographic database by storing, in said geographic database, data that indicate the line segments and circular arcs that form the shape of the road segment along the length thereof. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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11. A computer-readable medium having a geographic database formed according to process comprising:
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providing data indicating a shape of a road segment along a length thereof; forming a transform of the shape by determining an angle made with a fixed line by a tangent to the shape at each point along the length to provide a plurality of tangent angles; forming a plot of the tangent angles at each point along the length of the road segment against the length along the road segment; determining straight lines that correspond to said plot; using the straight lines that correspond to the plot to determine at least one of line segments and circular arcs that form the shape of the road segment along the length thereof; and representing said road segment in the geographic database by storing, in said geographic database, a data structure that indicates the line segments and circular arcs that form the shape of the road segment along the length thereof.
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12. A process for forming a geographic database comprising:
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obtaining data that represent a shape of a road; plotting a curve that corresponds to the shape of the road; determining a ψ
-s transform of the curve, wherein the ψ
-s transform is a plot of a tangent angle, wherein the angle of the tangent angle is made with a fixed line by a tangent to the curve along a length thereof;determining straight line portions of the ψ
-s transform;using the straight line portions of the ψ
-s transform to determine at least one corresponding straight lines and circular arcs that approximate the curve that corresponds to the shape of the road; andstoring data that indicate the straight lines and circular arcs that approximate the curve that corresponds to the shape of the road in order to represent the road. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A computer-readable medium having a geographic database formed according to process comprising:
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obtaining data that represent a shape of a road; plotting a curve that corresponds to the shape of the road; determining a ψ
-s transform of the curve, wherein the ψ
-s transform is plot of a tangent angle, wherein the angle of the tangent angle is made with a fixed line by a tangent to the curve along a length thereof;determining straight line portions of the ψ
-s transform;using the straight line portions of the ψ
-s transform to determine at least one corresponding straight lines and circular arcs that approximate the curve that corresponds to the shape of the road; andstoring a data structure that indicates the straight lines and circular arcs that approximate the curve that corresponds to the shape of the road in order to represent the road.
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20. A method comprising:
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providing data indicating a shape of a complex curve along a length thereof; forming a transform of the shape by determining an angle made with a fixed line by a tangent to the shape along the length thereof to provide a plurality of tangent angles; forming a plot of the tangent angles along the length of the complex curve against the length along the complex curve; determining at least one geometrical shape that fit said plot; using said at least one geometrical shape to determine at least one of a line, a circular arc and a clothoidal arc that form the shape of the complex curve along the length thereof; and storing data that indicate the at least one of a line, a circular arc and a clothoidal arc that form the shape of the complex curve along the length thereof. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. A computer-readable medium having computer-executable instructions for performing the steps of:
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providing data indicating a shape of a complex curve along a length thereof; forming a transform of the shape by determining an angle made with a fixed line by a tangent to the shape along the length thereof to provide a plurality of tangent angles; forming a plot of the tangent angles along the length of the complex curve against the length along the complex curve; determining at least one geometrical shape that fit said plot; and using said at least one geometrical shape to determine at least one of a line, a circular arc and a clothoidal arc that form the shape of the complex curve along the length thereof; and
storing data that indicate at least one of a line, a circular arc and a clothoidal arc that form the shape of the complex curve along the length thereof.
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Specification