Package com.luciad.projection

Class TLcdGnomonic

java.lang.Object
com.luciad.projection.ALcdProjection
com.luciad.projection.ALcdAzimuthal
com.luciad.projection.TLcdGnomonic
All Implemented Interfaces:
ILcdAzimuthal, ILcdProjection, ILcdPropertyChangeSource, Serializable, Cloneable
public class TLcdGnomonic extends ALcdAzimuthal
Gnomonic projection.

Introduction

This projection is an azimuthal and perspective projection from the center of the globe onto a plane tangent to the surface in a point.

Properties

  • All meridians and the equator are straight lines. In fact all great circles are shown as straight lines.
  • The shortest route between any two points on the surface of a sphere corresponds to the shortest route on the map. This stems from the fact that the shortest route between any two points on a sphere lies on a great circle. Therefore it is projected as a straight line. This seems to be the only useful feature of this projection.
  • Directions from the center of the projection are true.
  • The projection is neither conformal nor equal-area.
  • Less than a hemisphere can be shown on the map.

Example

Sample code


 ILcdProjection projection =
     new TLcdGnomonic(20.0, -50.0);

Implementation aspects

The equations of the gnomonic projection are taken from [Snyder1987].

Limitations

In practice only the spherical form is used. So, only the spherical form is implemented.

See Also:

  • Constructor Details

    • TLcdGnomonic

      public TLcdGnomonic()
      Constructs a gnomonic projection for the sphere with the origin at a point (0.0, 0.0).

    • TLcdGnomonic

      public TLcdGnomonic(double aLongitude, double aLatitude)
      Constructs a gnomonic projection for the sphere with the origin at a point (aLatitude, aLongitude). The central meridian is at aLongitude.
      Parameters:
      aLongitude - longitude of the origin of the projection, in decimal degrees.
      aLatitude - latitude of the origin of the projection, in decimal degrees.

    • TLcdGnomonic

      public TLcdGnomonic(ILcdPoint aOrigin)
      Constructs a gnomonic projection for a sphere with the origin at an ILcdPoint aOrigin. The central meridian is at aOrigin.getX().
      Parameters:
      aOrigin - ILcdPoint of the origin of the projection. No side effects will happen to the projection as a result from external changes to aOrigin.

  • Method Details

    • calculateCachedValues

      protected void calculateCachedValues()
      Description copied from class: ALcdAzimuthal
      Constants based on the point of origin of the projection don't have to be recalculated every time a method is called. They only have to be calculated when the projection properties change. Within the methods the pre-calculated values then can be used in order to gain efficiency.
      Overrides:
      calculateCachedValues in class ALcdAzimuthal

    • isAllInBounds

      public boolean isAllInBounds()
      Description copied from interface: ILcdProjection
      If all geodetic coordinates (l ,j ) are projected (visible) by an ILcdProjection and all (x,y ) coordinates are bounded this is true. All ILcdProjection objects have bounded (x,y ) coordinates because the projection is cut off if necessary.
      Returns:
      true if all LonLatPoints are within the bounds of the projection, false otherwise.

    • lonlatheight2worldOnSphereSFCT

      public void lonlatheight2worldOnSphereSFCT(ILcdPoint aLLHP, double aRadius, ILcd2DEditablePoint aXYPointSFCT) throws TLcdOutOfBoundsException
      Description copied from interface: ILcdProjection
      Transforms an ILcd2DEditablePoint on a sphere into the cartesian coordinate system of the projection.
      Parameters:
      aLLHP - point to be projected.
      aRadius - radius of the sphere (meters).
      aXYPointSFCT - projected point as side effect.
      Throws:
      TLcdOutOfBoundsException - If the ILcdPoint aLLHP is not within the valid area of the projection (visible area), then this exception is thrown.

    • world2lonlatOnSphereSFCT

      public void world2lonlatOnSphereSFCT(ILcdPoint aXYPoint, double aRadius, ILcd2DEditablePoint aLLPSFCT) throws TLcdOutOfBoundsException
      Description copied from interface: ILcdProjection
      Transforms an ILcdPoint from the cartesian coordinate system of the projection into an ILcd2DEditablePoint onto a sphere.
      Parameters:
      aXYPoint - projected point for which the corresponding geodetic point is sought.
      aRadius - radius of the sphere (meters).
      aLLPSFCT - resulting geodetic coordinate as side effect.
      Throws:
      TLcdOutOfBoundsException - If the ILcdPoint aXYPoint is not within the valid area of the projection (visible area), then this exception is thrown.

    • inLonLatBounds

      public boolean inLonLatBounds(ILcdPoint aLLP)
      Description copied from interface: ILcdProjection
      Checks if an ILcdPoint is inside the valid area of geodetic coordinates of the projection. The valid area is determined by the LonLatPoints that are visible and for which the corresponding cartesian coordinate is within the boundaries.
      Parameters:
      aLLP - ILcdPoint to be checked upon.
      Returns:
      true if valid, false if invalid.

    • boundaryLons

      public double[][] boundaryLons(double aLat)
      Description copied from class: ALcdProjection
      Default implementation. To be redefined for specific projections.
      Specified by:
      boundaryLons in interface ILcdProjection
      Overrides:
      boundaryLons in class ALcdProjection
      Parameters:
      aLat - latitude in decimal degrees and -90.0 <= aLat<= 90.0.
      Returns:
      the array of pairs of longitudes[0] and longitudes[1], where the closed interval longitudes[0] -> longitudes[1] is in visible area and -180.0 <= lon[i] <= 180.0.

    • boundaryLats

      public double[][] boundaryLats(double aLon)
      Description copied from class: ALcdProjection
      Default implementation. To be redefined for specific projections.
      Specified by:
      boundaryLats in interface ILcdProjection
      Overrides:
      boundaryLats in class ALcdProjection
      Parameters:
      aLon - longitude in decimal degrees -180.0 <= lon <= 180.0 .
      Returns:
      the array of pairs of latitudes lats[0] and lats[1], where the closed interval lats[0] -> lats[1] is in visible area and -90.0 <= lats[i] <= 90.0 .

    • inWorldBoundsOnSphere

      public boolean inWorldBoundsOnSphere(ILcdPoint aXYPoint, double aRadius)
      Description copied from interface: ILcdProjection
      Checks if a ILcdPoint is inside the valid cartesian area of the projection. The valid cartesian area is determined naturally by the projection bounds or by an artificial introduced boundary limit because some cartesian points are at infinity. The shape of the valid cartesian area is in many cases rectangular or circular although it might be more complex.
      Parameters:
      aXYPoint - point to be checked upon.
      aRadius - radius of the sphere.
      Returns:
      true if valid, false if invalid.

    • world2DEditableBoundsOnSphereSFCT

      public void world2DEditableBoundsOnSphereSFCT(double aRadius, ILcd2DEditableBounds aWorldBound)
      Less than one hemisphere is shown around the center of the projection.
      Parameters:
      aRadius - radius of the sphere.
      aWorldBound - the bounds of the projection in world coordinates as side effect.

    • toString

      public String toString()
      Returns the String representation of the gnomonic projection.
      Specified by:
      toString in interface ILcdProjection
      Overrides:
      toString in class Object
      Returns:
      the String representation of the gnomonic projection.