Package cds.healpix

Interface Projection

All Known Implementing Classes:
Healpix

public interface Projection
Define a projection of spherical coordinates (in the unit sphere) to the Euclidean plane, together with the reverse operation. Remark: we use arrays instead of objects because HEALPix is a low level library focused on performances. Accessing an element in an array is faster than accessing a class attribute.
Author:
F.-X. Pineau
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    Index of the lattitude in the array containing the result of an unproject method.
    static final int
    Index of the longitude in the array containing the result of an unproject method.
    static final int
    Index of the x coordinate in the array containing the result of a project method.
    static final int
    Index of the y coordinate in the array containing the result of a project method.
  • Method Summary

    Modifier and Type
    Method
    Description
    double[]
    project(double lonRad, double latRad)
    Project the given spherical coordinates into the Euclidean plane.
    void
    project(double lonRad, double latRad, double[] resultXY)
    See project(double, double) with the result stored in the given array.
    double[]
    unproject(double x, double y)
    Reverse projection: we look for spherical coordinates from their projected coordinates (project(double, double).
    void
    unproject(double x, double y, double[] resultLonLat)
    See unproject(double, double) with the result stored in the given array.
  • Field Details

    • LON_INDEX

      static final int LON_INDEX
      Index of the longitude in the array containing the result of an unproject method.
      See Also:
    • LAT_INDEX

      static final int LAT_INDEX
      Index of the lattitude in the array containing the result of an unproject method.
      See Also:
    • X_INDEX

      static final int X_INDEX
      Index of the x coordinate in the array containing the result of a project method.
      See Also:
    • Y_INDEX

      static final int Y_INDEX
      Index of the y coordinate in the array containing the result of a project method.
      See Also:
  • Method Details

    • project

      double[] project(double lonRad, double latRad)
      Project the given spherical coordinates into the Euclidean plane.
      Parameters:
      lonRad - longitude in radians (the accepted value range is implementation dependent)
      latRad - latitude in [-pi/2, pi/2] radians
      Returns:
      the projection of the given spherical coordinate into the Euclidean plane. The x and y coordinate are stored in the returned array at indices X_INDEX and Y_INDEX respectively. The range of possible value for x and y is implementation dependent.
    • project

      void project(double lonRad, double latRad, double[] resultXY)
      See project(double, double) with the result stored in the given array.
      Parameters:
      lonRad - see project(double, double)
      latRad - see project(double, double)
      resultXY - array used to store the result. Must be of size >= 2.
    • unproject

      double[] unproject(double x, double y)
      Reverse projection: we look for spherical coordinates from their projected coordinates (project(double, double).
      Parameters:
      x - the x coordinate of the projected spherical point we are looking for, the accepted value range is implementation dependent
      y - the y coordinate of the projected spherical point we are looking for, must be in [-2, 2].
      Returns:
      the spherical coordinates leading to the given projection coordinates. The lon and lat coordinate are stored in the returned array at indices LON_INDEX and LAT_INDEX respectively. Lat is in [-pi/2, pi/2] radians, lon is also in radians but it possible value range is implementation dependent).
    • unproject

      void unproject(double x, double y, double[] resultLonLat)
      See unproject(double, double) with the result stored in the given array.
      Parameters:
      x - unproject(double, double)
      y - unproject(double, double)
      resultLonLat - array used to store the result. Must be of size >= 2.