TECHNIQUES FOR DRAWING GEODETIC POLYGONS

• US 20110090254A1
• Filed: 10/20/2009
• Published: 04/21/2011
• Est. Priority Date: 10/20/2009
• Status: Active Grant

• Current Assignee: Palantir Technologies Incorporated
• Original Assignee: Palantir Technologies Incorporated
• Inventors: Carrino, John Antonio, Cervelli, Daniel Patrick
• Granted Patent: US 8,085,268 B2
• Time in Patent Office: Days
• US Class Current: 345/634
• CPC Class Codes: G09B 29/005 Map projections or methods associated specifically therewith

Abstract

Techniques in a data processor for drawing on a map a geodetic polygon that straddles a splitting meridian include, in one embodiment, maintaining data that represents the geodetic polygon, the data comprising a set of geographic coordinates; transforming the set of geographic coordinates into a set of planar coordinates representing a planar polygon; splitting the planar polygon into a plurality of sub-figures; shifting at least one sub-figure of the plurality of sub-figures along a horizontal axis of two-dimensional plane to produce a shifted sub-figure; and causing the shifted sub-figure to be displayed on a map concurrently with at least one other sub-figure of the plurality of sub-figures that was not shifted.

Claims

1. A method for drawing a geodetic polygon on a map, comprising:

maintaining data that represents a geodetic polygon, the data comprising a set of geographic coordinates representing vertices of the geodetic polygon;

transforming the set of geographic coordinates into a set of planar coordinates representing vertices of a planar polygon;

dividing the planar polygon into a plurality of sub-figures;

shifting at least one sub-figure of the plurality of sub-figures along a horizontal axis of two-dimensional plane to produce a shifted sub-figure; and

causing the shifted sub-figure to be displayed on a map concurrently with at least one other sub-figure of the plurality of sub-figures that was not shifted;

wherein the method is performed by one or more computing devices.

2. The method of claim 1, wherein transforming the set of geographic coordinates into a set of planar coordinates representing a planar polygon comprises:

proceeding counter-clockwise from a vertex A of the geodetic polygon to an adjacent vertex B of the geodetic polygon;

wherein vertex A and vertex B each correspond to a geographic coordinate in the set of geographic coordinates;

transforming the geographic coordinate corresponding to vertex A to a planar coordinate A′

;

transforming the geographic coordinate corresponding to vertex B to a planar coordinate B′

;

calculating a distance along the horizontal axis between planar coordinate A′ and

planar coordinate B′

; and

determining that the geodetic polygon straddles a splitting meridian of said map by determining that said distance is greater than one-half a horizontal extent of the map along the horizontal axis.

3. The method of claim 2, wherein transforming the set of geographic coordinates into a set of planar coordinates representing a planar polygon further comprises:

calculating an adjusted planar coordinate B″

based on a difference between (1) said distance along the horizontal axis and (2) the horizontal extent of the map along the horizontal axis; and

wherein said set of planar coordinates representing said planar polygon includes planar coordinate A′ and

adjusted planar coordinate B″

but does not include planar coordinate B′

.

4. The method of claim 3, wherein the x-value of adjusted planar coordinate B″

is based on the x-value of planar coordinate A′ and

said difference.

5. The method of claim 4, wherein the x-value of adjusted planar coordinate B″

places adjusted planar coordinate B″

along the horizontal axis to the right of the right-most boundary of said map.

6. The method of claim 5, wherein the x-value of adjusted planar coordinate B″

places adjusted planar coordinate B″

along the horizontal axis to the left of the left-most boundary of said map.

7. The method of claim 1, wherein at least one planar coordinate of said planar polygon has an x-value that places the at least one planar coordinate along the horizontal axis to the right of the right-most boundary of said map.

8. The method of claim 7, wherein at least one other planar coordinate of said planar polygon has an x-value that places the at least one other planar coordinate along the horizontal axis to the left of the left-most boundary of said map.

9. The method of claim 1, wherein splitting the planar polygon into a plurality of sub-figures comprises splitting the planar polygon along the right-most boundary of said map to form two sub-figures comprising the planar polygon.

10. The method of claim 1, wherein splitting the planar polygon into a plurality of sub-figures comprises splitting the planar polygon along the right-most boundary and the left-most boundary of said map to form three sub-figures comprising the planar polygon.

11. The method of claim 1, wherein shifting the at least one sub-figure of the plurality of sub-figures along the horizontal axis comprises:

shifting the at least one sub-figure of the plurality of sub-figures along the horizontal axis by an amount corresponding to the horizontal extent of the map along the horizontal axis.

12. The method of claim 11, wherein the shifted sub-figure has a plurality of vertices having y-values along a vertical axis in the two-dimensional plane equal to the y-values along the vertical axis of the vertices of the at least one sub-figure, and wherein the x-values along the horizontal axis of the vertices of the shifted sub-figure are offset from the x-values along the horizontal axis of the vertices of the at least one sub-figure by an amount equal to the horizontal extent of the map along the horizontal axis.

13. The method of claim 1, wherein the geographic coordinates are maintained in terms of latitude and longitude.

14. The method of claim 1, wherein the set of geographic coordinates are transformed into the set of planar coordinates using a cylindrical projection mapping function selected from the group consisting of a Mercator projection mapping function, a cylindrical equidistant projection mapping function, and a Miller cylindrical projection mapping function.

15. A computer-readable storage medium storing instructions for drawing a geodetic polygon on a map, the instructions, when executed by one or more computing devices, cause the one or more computing devices to perform a method comprising:

maintaining data that represents a geodetic polygon, the data comprising a set of geographic coordinates representing vertices of the geodetic polygon;

transforming the set of geographic coordinates into a set of planar coordinates representing vertices of a planar polygon;

dividing the planar polygon into a plurality of sub-figures;

shifting at least one sub-figure of the plurality of sub-figures along a horizontal axis of two-dimensional plane to produce a shifted sub-figure; and

causing the shifted sub-figure to be displayed on a map concurrently with at least one other sub-figure of the plurality of sub-figures that was not shifted.

16. The computer-readable storage medium of claim 15, wherein transforming the set of geographic coordinates into a set of planar coordinates representing a planar polygon comprises:

proceeding counter-clockwise from a vertex A of the geodetic polygon to an adjacent vertex B of the geodetic polygon;

wherein vertex A and vertex B each correspond to a geographic coordinate in the set of geographic coordinates;

transforming the geographic coordinate corresponding to vertex A to a planar coordinate A′

;

transforming the geographic coordinate corresponding to vertex B to a planar coordinate B′

;

calculating a distance along the horizontal axis between planar coordinate A′ and

planar coordinate B′

; and

determining that the geodetic polygon straddles a splitting meridian of said map by determining that said distance is greater than one-half a horizontal extent of the map along the horizontal axis.

17. The computer-readable storage medium of claim 16, wherein transforming the set of geographic coordinates into a set of planar coordinates representing a planar polygon further comprises:

calculating an adjusted planar coordinate B″

based on a difference between (1) said distance along the horizontal axis and (2) the horizontal extent of the map along the horizontal axis; and

wherein said set of planar coordinates representing said planar polygon includes planar coordinate A′ and

adjusted planar coordinate B″

but does not include planar coordinate B′

.

18. The computer-readable storage medium of claim 17, wherein the x-value of adjusted planar coordinate B″

is based on the x-value of planar coordinate A′ and

said difference.

19. The computer-readable storage medium of claim 18, wherein the x-value of adjusted planar coordinate B″

places adjusted planar coordinate B″

along the horizontal axis to the right of the right-most boundary of said map.

20. The computer-readable storage medium of claim 19, wherein the x-value of adjusted planar coordinate B″

places adjusted planar coordinate B″

along the horizontal axis to the left of the left-most boundary of said map.

21. The computer-readable storage medium of claim 15, wherein at least one planar coordinate of said planar polygon has an x-value that places the at least one planar coordinate along the horizontal axis to the right of the right-most boundary of said map.

22. The computer-readable storage medium of claim 21, wherein at least one other planar coordinate of said planar polygon has an x-value that places the at least one other planar coordinate along the horizontal axis to the left of the left-most boundary of said map.

23. The computer-readable storage medium of claim 15, wherein splitting the planar polygon into a plurality of sub-figures comprises splitting the planar polygon along the right-most boundary of said map to form two sub-figures comprising the planar polygon.

24. The computer-readable storage medium of claim 15, wherein splitting the planar polygon into a plurality of sub-figures comprises splitting the planar polygon along the right-most boundary and the left-most boundary of said map to form three sub-figures comprising the planar polygon.

25. The computer-readable storage medium of claim 15, wherein shifting the at least one sub-figure of the plurality of sub-figures along the horizontal axis comprises:

shifting the at least one sub-figure of the plurality of sub-figures along the horizontal axis by an amount corresponding to the horizontal extent of the map along the horizontal axis.

26. The computer-readable storage medium of claim 25, wherein the shifted sub-figure has a plurality of vertices having y-values along a vertical axis in the two-dimensional plane equal to the y-values along the vertical axis of the vertices of the at least one sub-figure, and wherein the x-values along the horizontal axis of the vertices of the shifted sub-figure are offset from the x-values along the horizontal axis of the vertices of the at least one sub-figure by an amount equal to the horizontal extent of the map along the horizontal axis.

27. The computer-readable storage medium of claim 15, wherein the geographic coordinates are maintained in terms of latitude and longitude.

28. The computer-readable storage medium of claim 15, wherein the set of geographic coordinates are transformed into the set of planar coordinates using a cylindrical projection mapping function selected from the group consisting of a Mercator projection mapping function, a cylindrical equidistant projection mapping function, and a Miller cylindrical projection mapping function.

29. A geodetic polygon drawing computer system comprising:

memory configured to store data that represents a geodetic polygon, the data comprising a set of geographic coordinates representing vertices of the geodetic polygon;

transformation logic coupled to the memory and configured to transform a state of the memory by transforming the set of geographic coordinates into a set of planar coordinates representing vertices of a planar polygon;

planar polygon splitting logic coupled to the transformation logic and configured to further transform the state of the memory by dividing the planar polygon into a plurality of sub-figures;

shifting logic coupled to the planar polygon splitting logic and configured to further transform the state of the memory by shifting at least one sub-figure of the plurality of sub-figures along a horizontal axis of two-dimensional plane to produce a shifted sub-figure; and

display driving logic configured to cause displaying, on a computer display unit, the shifted sub-figure on a map concurrently with at least one other sub-figure of the plurality of sub-figures that was not shifted.