Selective polygon map display method

• US 5,475,802 A
• Filed: 05/12/1994
• Issued: 12/12/1995
• Est. Priority Date: 01/31/1990
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Wescott, Thomas F., McCleary, Lawrence E., Nation, David A.
• Primary Examiner(s): Herndon, Heather R.
• Assistant Examiner(s): VO, CLIFF N
• Application Number:
  US08/243,650
• Time in Patent Office: 579 Days
• Field of Search: 395/133, 395/129, 395/125, 395/130, 395/131, 395/123, 395/134, 395/135, 395/138
• US Class Current: 345/441
• CPC Class Codes: G06T 17/05 Geographic models
• CPC Class Codes: G09B 29/005 Map projections or methods associated specifically therewith

Abstract

Signal transformations of inputted data brought about by 58 new subroutines in combination with other subroutines to display world maps or other display items with the unique capability of performing the following functions in complete generality. (1) Arbitrary selection of map center and coverage, including global displays, (2) filling of all land and lake areas defined by polygons composed of an arbitrary number of vertices, (3) clipping of map features and overlays at map boundaries and poles, (4) selection from any of nineteen currently implemented map projections with provision to install any other projection topologically similar to an oblique conic, (5) calculation of latitude/longitude for any point on a map without the need for inverse mapping equations, and (6) an efficient method of plotting polyline segments along great circles. These are a number of feature functions provided by this inventive concept.

The software could potentially be used with any digital global geographic data base, such as World Data Bank II (WDBII), a geographic information system or other data base where polylines are used to depict linear and/or areal features. Polygon (region filled) maps and other display items can be constructed from any data base from which closed polygons can be extracted directly, or constructed via additional processing.

Claims

1. A method of displaying areal features which is represented by polygon fill of vector data for world maps and other display items by signal transformations of data representative of areal features from which polygons are extracted comprising the steps of:

feeding said data representative of areal features from which polygons are extractable to a computer;

establishing from said data representative of areal features in said computer, display geographic coordinate relationships for display and interrogation;

transforming said data representative of areal features in said computer, into a great circle polygon format for display;

selecting from said data representative of areal features in said computer, background and overlay features for display;

determining from said data representative of areal features in said computer, spatial relationships between spherical polygons for display;

processing said data representative of areal features in said computer, to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features in a plane;

clipping polygons from said data representative of areal features in said computer, by lines so that portions thereof are dipslayable as separate entities;

projecting from said data representative of areal features in said computer, geographic coordinates onto a defined map display;

providing transformations from display coordinates to latitude and longitude coordinates for the display thereof, said transformations being derived from said data representative of areal features in said computer; and

displaying a representation based on said data representative of areal features in said computer.

2. A method according to claim 1 further includes the step of:

designating the choice of the displayed transformation of providing.

3. A method according to claim 2 in which said step of establishing geographic coordinate relationships is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors.

4. A method according to claim 3 in which said step of transforming into a great circle polygon format for display includes where individual line segments are defined as particular geographic curves no is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of curved segments.

5. A method according to claim 4 in which said step of selecting background and overlay features for display comprises the selection of areal data from a filled outline of the world and other areal features including political districts and satellite footprints.

6. A method according to claim 5 in which said step of determining spatial relationships between spherical polygons for display includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point, convex property, and minimum bounding small circle.

7. A method according to claim 6 in which said processing to provide clipping and singularity removal at the map interruption lines to allow the display of curved surface features in a plane is predetermined to avoid errors and anomalous behavior in any filled areal features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection.

8. A method according to claim 7 in which said step of clipping polygons by lines provides for the display of portions as separate entities to allow polygons of virtually any number of vertices to be subjected to said clipping and singularity removal to automatically subdivide sections of the input polygon as required to limit the maximum number of output vertices to a count compatible with the polygon fill capacity of a particular display device interface.

9. A method according to claim 8 in which said step of projecting geographic coordinates onto a defined map display applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, Oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographic, Sinusoidal, Stereographic and Universal Transverse Mercator.

10. A method according to claim 9 in which said step of providing transformations solves the inverse by a generic method applicable to any azimuthal, conic, cylindrical and pseudocylindrical projection and requires input of a mathematical transformation defining a specific projection and some point on that specific projection.

11. A method according to claim 1 in which said step of establishing display geographic coordinate relationships is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors, said step of transforming into a great circle polygon format for display includes where individual line segments are defined as particular geographic curves and is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of curved segments, said step of selecting background and overlay features for display is from a filled outline of the world and other areal features including political districts and satellite footprints, said step of determining spatial relationships between spherical polygons for display includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point, convex property, and minimum bounding small circle, said step of processing to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features in a plane is predetermined to avoid errors and anomalous behavior in any filled areal features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection, said step of clipping polygons by lines and great circles provides for the display of portions as separate entities to allow polygons of virtually any number of vertices to be subjected to said clipping and singularity removal to automatically subdivide sections of the input polygon as required to limit the maximum number of output vertices to a count compatible with the polygon fill capacity of a particular display device interface, said step of projecting geographic coordinates onto a defined map display applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, Oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographic, Sinusoidal, Stereographic and Universal Transverse Mercator and said step of providing transformations solves the inverse by a generic method applicable to any azimuthal, conic, cylindrical and pseudocylindrical projection and requires input of a mathematical transformation defining a specific projection and some point on that specific projection.

12. A method of displaying areal features which is represented by polygon fill of vector data for world maps and other display items by signal transformations of data representative of areal features from which polygons are extracted comprising the steps of:

feeding said data representative of areal features from which polygons are extractable to a computer;

establishing from said data representative of areal features in said computer, geographic coordinate relationships for display and interrogation;

transforming said data representative of areal features in said computer, into a great circle polygon format for display;

selecting from said data representative of areal features in said computer, background and overlay features for display;

determining from said data representative of areal features in said computer, spatial relationships between spherical and loxodrome polygons for display;

processing said data representative of areal features in said computer, to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features on a plane;

clipping polygons from said data representative of areal features in said computer, by lines and great circles so that portions thereof are displayable as separate entities;

projecting from said data representative of areal features in said computer, geographic coordinates onto a graphic device for the display thereof;

providing transformations from any location on a map from an input of a map location and an input of a transformation defining a specific projection that solves an inverse transformation by a generic method applicable to any azimuthal, conic, cylindrical, and pseudocylindrical projection, said transformations being derived from data mapped into a specific projection from said data representative of areal features in said computer; and

displaying a representation based on said data representative of areal features in said computer.

13. A method according to claim 12 in which said step of establishing geographic coordinate relationships is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors.

14. A method according to claim 13 in which said step of transforming into a great circle polygon format for display includes where individual line segments are defined as particular geographic curves and is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of the curved segments.

15. A method according to claim 14 in which said step of selecting background and overlay features for display is from a filled outline of the world and other areal features including political districts and satellite footprints.

16. A method according to claim 15 in which said step of determining spatial relationships between spherical polygons for display includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point, convex property, and minimum bounding small circle.

17. A method according to claim 16 in which said step of processing to provide clipping and singularity removal at the map interruption lines to allow the display of curved surface features in a plane is predetermined to avoid errors and anomalous behavior in any filled areal features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection.

18. A method according to claim 17 in which said step of clipping polygons by lines provides for the display of portions as separate entities to allow polygons of virtually any number of vertices to be subjected to said clipping and singularity removal to automatically subdivide sections of the input polygon as required to limit the maximum number of output vertices to a count compatible with the polygon fill capacity of a particular display device interface.

19. A method according to claim 18 in which said step of projecting geographic coordinates onto a defined map display applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, Oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographic, Sinusoidal, Stereographic and Universal Transverse Mercator.

20. A method according to claim 19 in which said step of providing transformations solves the inverse by a generic method appplicable to any azimuthal, conic, cylindrical and pseudocylindrical projection and requires input of a mathematical transformation defining a specific projection and some point on that specific projection.

21. A method of displaying linear features which is represented by polyline plotting of linear vector data for world maps and other display items by signal transformations of data representative of linear features from which polylines are extracted comprising the steps of:

feeding said data representative of linear features from which polylines are extractable to a computer;

establishing from said data representative of linear features in said computer, display geographic coordinate relationships;

transforming said data representative of linear features in said computer, into a great circle polyline format for display;

selecting from said data representative of linear features in said computer, background and overlay features for display;

determining from said data representative of linear features in said computer, spatial relationships between polylines and spherical polygons for display;

processing said data representative of linear features in said computer, to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features in a plane;

clipping polylines from said data representative of linear features in said computer, by lines and great circles so that portions thereof are displayable as separate entities;

projecting from said data representative of linear features in said computer, geographic coordinates onto a defined map display;

providing transformations from display coordinates to latitude and longitude coordinates for the display thereof, said transformations being derived from said data representative of linear features in said computer; and

displaying a representation based on said data representative of areal features in said computer.

22. A method according to claim 21 further includes the step of:

designating the choice of the displayed transformation of providing.

23. A method according to claim 22 in which said step of establishing geographic coordinate relationships is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors.

24. A method according to claim 23 in which said step of transforming into a great circle polyline format for display includes where individual line segments are defined as particular geographic curves and is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of curved segments.

25. A method according to claim 24 in which said step of selecting background and overlay features for display is from linear features including the world outline, vehicle paths and range rings.

26. A method according to claim 25 in which said step of determining spatial relationships between polylines and spherical polygons for display includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point and minimum bounding small circle.

27. A method according to claim 26 in which said step of processing to provide clipping and singularity removal at the map interruption lines to allow the display of curved surface features in a plane is predetermined to avoid errors and anomalous behavior in any linear features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection.

28. A method according to claim 27 in which said step of clipping polygons by lines provides for the display of portions as separate entities.

29. A method according to claim 28 in which said step of projecting geographic coordinates onto a defined map display applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, Oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographic, Sinusoidal, Stereographic and Universal Transverse Mercator.

30. A method according to claim 29 in which said step of providing transformations solves the inverse by a generic method applicable to any azimuthal, conic, cylindrical and pseudocylindrical projection and requires input of a mathematical transformation defining a specific projection and some point on that specific projection.

31. A method according to claim 21 in which said step of establishing is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors, said step of transforming into a great circle polyline format for display included where individual line segments are defined as particular geographic curves and is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of curved segments, said step of selecting background and overlay features for display is from linear features including the world outline, vehicle paths and range rings, said step of determining spatial relationships between polylines and spherical polygons for display includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point and minimum bounding small circle, said step of processing to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features in a plane is predetermined to avoid errors and anomalous behavior in any linear features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection, said step of clipping polylines by lines and great circles provides for the display of portions as separate entities, said step of projecting geographic coordinates onto a defined map display applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, Oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographic, Sinusoidal, Stereographic and Universal Transverse Mercator and said step of providing transformations solves the inverse by a generic method applicable to any azimuthal, conic, cylindrical and pseudocyclindrical projection and requires input of a mathematical transformation defining a specific projection and some point on that specific projection.

32. A method of displaying linear features which is represented by polyine plotting of linear vector data for world maps and other display items by signal transformations of data representative of linear features from which polylines are extracted comprising the steps of:

feeding said data representative of linear features from which polylines are extractable to a computer;

establishing from said data representative of linear features in said computer, geographic coordinate relationships for display and interrogation;

transforming said data representative of linear features in said computer, into a great circle polyline format for display;

selecting from said data representative of linear features in said computer, background and overlay features for display;

determining from said data representative of linear features in said computer, spatial relationships between polylines, spherical polygons and loxodrome polygons for display;

processing said data representative of linear features in said computer, to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features on a plane;

clipping polylines from said data representative of linear features in said computer, by lines and great circles so that portions thereof are displayable as separate entities;

projecting from said data representative of linear features in said computer, geographic coordinates onto a graphic device;

providing transformations from any location on a map from an input of a map location and an input of a transformation defining a specific projection that solves an inverse transformation by a generic method applicable to any azimuthal, conic, cylindrical, and pseudocylindrical projection, said transformations being derived from data mapped into a specific projection from said data representative of linear features in said computer; and

displaying a representation based on said date representative of areal features in said computer.

33. A method according to claim 32 in which said step of establishing geographic coordinate relationships is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors.

34. A method according to claim 33 in which said step of transforming into a great circle polyline format for display includes where individual line segments are defined as particular geographic curves and is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of the curved segments.

35. A method according, to claim 34 in which said step of selecting background and overlay features of display is from linear features including the world outline, vehicle paths and range rings.

36. A method according to claim 35 in which said step of determining spatial relationships between polylines, spherical polygons and loxodrome polygons for display includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point and minimum bounding small circle.

37. A method according to claim 36 in which said step of processing to provide clipping and singularity removal at the map interruption lines to allow the display of curved surface features in a plane is predetermined to avoid errors and anomalous behavior in any linear features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection.

38. A method according to claim 37 in which said step of clipping polylines by lines and great circles provides for the display of portions as separate entities.

39. A method according to claim 38 in which said step of projecting geographic coordinates onto a defined map display applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, Oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographic, Sinusoidal, Stereographic and Universal Transverse Mercator.

40. A method according to claim 39 in which said step of providing transformations solves the inverse by a generic method applicable to any azimuthal, coinic, cylindrical and pseudocylindrical projection and relies upon input of a mathematical transformation defining a specific projection and some point on the specific projection.

41. A method of displaying areal features which is represented by polygon fill of vector data by signal transformations of data representative of areal features from which polygons are extracted comprising the steps of:

feeding the representative data to a computer;

establishing from said representative data display geographic coordinate relationships;

transforming said representative data into a great circle polygon format;

selecting from said representative data background and overlay features;

determining from said representative data spatial relationships between spherical polygons;

processing said representative data to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features in a plane;

clipping polygons from said representative data by lines and great circles so that portions thereof are displayable as separate entities;

projecting from said representative data geographic coordinates onto a defined map display;

providing transformations from display coordinates to latitude and longitude coordinates for the display thereof, said transformations being derived from said representative data; and

displaying a representation based on said data representative of areal features in said computer.

42. A method according to claim 41 further includes step of:

designating a choice of the displayed transformation of providing.

43. A method according to claim 41 in which said step of establishing is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors, said step of transforming into a great circle polygon format for display includes where individual line segments are defined as particular geographic curves and is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of curved segments, said step of selecting is from a filled outline of the world and other areal features including political districts and satellite footprints, said step of determining includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point, convex property, and minimum bounding small circle, said step of processing to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features in a plane is predetermined to avoid errors and anomalous behavior in any filled areal features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection, said step of clipping polygons by lines and great circles so that portions thereof are displayable as separate entities allows polygons of virtually any number of vertices to be subjected to said clipping and singularity removal to automatically subdivide sections of the input polygon as required to limit the maximum number of output vertices to a count compatible with the polygon fill capacity of a particular display device interface, said step of projecting applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographic, Sinusoidal, stereographic and Universal Transverse Mercator and said step of providing transformations solves the inverse by a generic method applicable to any azimuthal, conic cylindrical and pseudocylindrical projection and requires input of a mathematical transformation defining a specific projection and some point on that specific projection.

44. A method of displaying areal features which is represented polygon fill of vector data by signal transformations of data representative of areal features from which polygons are extracted comprising the steps of:

feeding the representative data to a computer;

establishing from said representative data geographic coordinate relationships for display and interrogation;

transforming said representative data into a great circle polygon format for display;

selecting from said representative data background and overlay features for display;

determining from said representative data spatial relationships between spherical and loxodrome polygons for display;

processing said representative data to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features on a plane;

clipping polygons from said representative data by lines and great circles so that portions thereof are displayable as separate entities;

projecting from said representative data geographic coordinates onto a graphic device for the display thereof;

providing transformations from any location on a map from an input of a map location and an input of a transformation defining a specific projection that solves an inverse transformation by a generic method applicable to any azimuthal, conic, cylindrical, and pseudocylindrical projection, said transformations being derived from data mapped into a specific projection from said representative data; and

displaying a representation based on said data representative of areal features in said computer.

45. A method according to claim 44 in which said step of establishing is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors.

46. A method according to claim 45 in which said step of transforming into a great circle polygon format for display includes where individual line segments are defined as particular geographic curves and is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of the curved segments.

47. A method according to claim 46 in which said step of selecting is from a filled outline of the world and other areal features including political districts and satellite footprints.

48. A method according to claim 47 in which said step of determining includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point, convex property, and minimum bounding small circle.

49. A method according to claim 48 in which said step of processing to provide clipping and singularity removal is predetermined to avoid errors and anomalous behavior in any filled areal features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection.

50. A method according to claim 49 in which said step of clipping polygons by lines provides for the display of portions as separate entities to allow polygons of virtually any number of vertices to be subjected to said clipping and singularity removal to automatically subdivide sections of the input polygon as required to limit the maximum number of output vertices to a count compatible with the polygon fill capacity of a particular display device interface.

51. A method according to claim 50 in which said step of projecting applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, Oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographick, Sinusoidal, Stereographic and Universal Transverse Mercator.

52. A method according to claim 51 in which said step of providing transformations solves the inverse by a generic method applicable to any azimuthal, conic, cylindrical and pseudocylindirical projection and relies upon input of a mathematical transformation defining a specific projection and some point on the specific projection.

53. A method of displaying linear features which is represented by polyline plotting of linear vector data by signal transformations of data representative of linear features from which polylines are extracted comprising the steps of:

feeding the representative data to a computer;

establishing from said representative data display geographic coordinate relationships;

transforming said representative data into a great circle polyline format;

selecting from said representative data background and overlay features;

determining from said representative data spatial relationships between polylines, spherical polygons and loxodrome polygons;

processing said representative data to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features in a plane;

clipping polylines from said representative data by lines and great circles so that portions thereof are displayable as separate entities;

projecting from said representative data geographic coordinates onto a defined map display;

providing transformations from display coordinates to latitude and longitude coordinates for the display thereof, said transformations being derived from said data representative of areal features; and

displaying a representation based on said data representative of areal features in said computer.

54. A method according to claim 53 further includes step of:

designating a choice of the displayed transformation of providing.

55. A method according to claim 53 in which said step of establishing is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors, said step of transforming into a great circle polyline format includes where individual line segments are defined as particular geographic curves and is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of curved segments, said step of selecting is from linear features including the world outline, vehicle paths and range rings, said step of determining includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point and minimum bounding small circle, said step of processing to provide clipping and singularity removal is predetermined to avoid errors and anomalous behavior in any linear features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection, said step of clipping polylines by lines and great circles provides for the display of portions as separate entities, said step of projecting applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, Oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographic, Sinusoidal, stereographic and Universal Transverse Mercator and said step of providing transformations solves the inverse by a generic method applicable to any azimuthal, conic, cylindrical and pseudocylindrical projection and requires input of a mathematical transformation defining a specific projection and some point on that specific projection.

56. A method of displaying linear features which is represented by polyline plotting of linear vector data by signal transformations of data representative of linear features from which polylines are extracted comprising the steps of:

feeding the representative data to a computer;

establishing from said representative data geographic coordinate relationships for display and interrogation;

transforming said representative data into a great circle polyline format for display;

selecting from said representative data background and overlay features for display;

determining from said representative data spatial relationships between polylines, spherical polygons and loxodrome polygons for display;

processing said representative data to provide clipping and singularity removal at map interruption lines to allow the display of curved surface features on a plane;

clipping polylines from said representative data by lines and great circles so that portions thereof are displayable as separate entities;

projecting from said representative data geographic coordinates onto a graphic device;

providing transformations from any location on a map from an input of a map location and an input of a transformation defining a specific projection that solves an inverse transformation by a generic method applicable to any azimuthal, conic, cylindrical, and pseudocylindrical projection, said transformations being derived data mapped into a specific projection from said representative data; and

displaying a representation based on said data representative of areal features in said computer.

57. A method according to claim 56 in which said step of establishing is independent of specific projection and provides generic calculation of intersection between the map display on a screen and loxodrome bounded geographic sectors.

58. A method according to claim 57 in which said step of transforming into a great polyline format for display includes where individual line segments are defined as particular geographic curves and is accomplished in a projection independent manner by adding points automatically as required by any specific projection to achieve accurate depiction of the curved segments.

59. A method according to claim 58 in which said selecting is from linear features including the world outline, vehicle paths and range rings.

60. A method according to claim 59 in which said step of determining spatial relationships is between polylines, spherical polygons and loxodrome polygons for display and includes finding intersection, enclosure, longitudinal relationships for points east of a longitudinal reference point and minimum bounding small circle.

61. A method according to claim 60 in which said step of processing to provide clipping and singularity removal at the map interruption lines to allow the display of curved surface features is in a plane and is predetermined to avoid errors and anomalous behavior in any linear features mapped from geographic coordinates onto a selected azimuthal, conical, and pseudocylindrical projection.

62. A method according to claim 61 in which said step of clipping polylines by lines and great circles is so that portions thereof are displayable as separate entities.

63. A method according to claim 62 in which said step of projecting geographic coordinates onto a defined map display applies to any azimuthal, conic, cylindrical, and pseudocylindrical projection including Albers Equal Area Conic, Azimuthal Equidistant, Azimuthal Equal Area, Equirectangular, Gnomonic, Equidistant Conic, Lambert Conformal Conic, Mercator, Miller, Oblique Mercator, Orthographic, Equatorial Orthographic, Polar Orthographic, Perspective Polyconic, Polar Stereographic, Sinusoidal, Stereographic and Universal Transverse Mercator.

64. A method according to claim 63 in which said step providing transformations solves the inverse by a generic method appplicable to any azimuthal, conic, cylindrical and pseudocylindrical projection and relies upon input of a mathematical transformation defining a specific projection, some point on the specific projection.