Package skyview.geometry.projecter

Class Toa

java.lang.Object
skyview.geometry.Transformer
skyview.geometry.Projecter
skyview.geometry.projecter.Toa
All Implemented Interfaces:
Serializable, Component
public class Toa extends Projecter
This class provides for the translation between coordinates and an HTM-based projection.

The projection is centered at the north pole. The south pole is projected to the four corners at (+/-1, +/-1). The equator projects to the diagonals running between the points (-1,0)->(0,1), (0,1)->(1,0), (1,0)->(0,-1), (-1,0)->(0,-1). These diagonals divide the four unit squares at the center of the coordinate grid into 8 right isoceles triangles.

The position 0,0 projects to 0,1 while the position 90,0 projects to 1,0. Note that in an astronomical projection the coordinates will normally have the X axis inverted, so that 0,0 will project to -1,0.

The 8 triangles correspond to the 8 initial triangles of the HTM decomposition of the sphere. The projection is defined such that the subtriangles in the HTM decomposition are mapped to isoceles right-triangles in the projection plane.

This call may be called in the same fashion as standard projections or it may be called to create a tile space. In this case the object immediately computes the coordinates corresponding to all pixels in a tile and later returns these as requested.

The tiles are numbered with tile 0,0 as the top, left tile. The vertical orientation of the tiles is therefore the opposite of the orientation of the pixel values within the tiles and within the FITS files generated. Note that when SkyView generates quicklook images it flips the Y-axis to accommodate the difference between the astronomical and imaging conventions.

See Also:

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    class 
    Toa.ToaDeproj
    Deproject from the ToastPlane back to the unit sphere

  • Constructor Summary

    Constructors
    Constructor
    Description
    Toa()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    double[]
    find(double lon, double lat)
     
    String
    getDescription()
    Get the description of this component.
    String
    getName()
    Get the name of this component.
    Deprojecter
    inverse()
    Get the inverse
    boolean
    isInverse(Transformer obj)
    Are these two transformations, inverses of each other? This method is used to optimize a series of transformations where transformations.
    static void
    main(String[] args)
     
    double[]
    project(double lon, double lat)
    Calculate the x,y corresponding to a given lon/lat
    void
    setPrecision(double epsilon, double minDelta)
    Specify precision used in non-grid project/deproject calculations
    double[]
    shadowPoint(double x, double y)
    Return a shadowpoint for the input location.
    static void
    show(String prefix, double[] vector)
     
    boolean
    straddle(double[][] vertices)
    Does this pixel go wrap around the standard region of the image? E.g., does it straddle the 180 deg in a Car or Ait projection?
    boolean
    straddleable()
    Is it possible for a pixel to straddle the valid region.
    double[][][]
    straddleComponents(double[][] vertices)
    If this is a straddling pixel, then return the straddle components
    double[][][]
    tile(int level, int ix, int iy, int subdiv)
     
    void
    transform(double[] unit, double[] plane)
    Convert a single point where the output vector is supplied.
    boolean
    validPosition(double[] plane)
    Is this a valid position in the projection plane for this image.

    Methods inherited from class skyview.geometry.Projecter

    allValid, getInputDimension, getOutputDimension, getXTiling, getYTiling, tissot

    Methods inherited from class skyview.geometry.Transformer

    transform, transform

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Toa

      public Toa()

  • Method Details

    • validPosition

      public boolean validPosition(double[] plane)
      Description copied from class: Projecter
      Is this a valid position in the projection plane for this image. This default is appropriate for all projections where the projection plane is infinite.
      Overrides:
      validPosition in class Projecter

    • setPrecision

      public void setPrecision(double epsilon, double minDelta)
      Specify precision used in non-grid project/deproject calculations

    • project

      public double[] project(double lon, double lat)
      Calculate the x,y corresponding to a given lon/lat
      Parameters:
      lon - The longitude in radians.
      lat - The latitude in radians.
      Returns:
      A pair of coordinates in the projection plane where there coordinates are in the range [-1,1].

    • find

      public double[] find(double lon, double lat)

    • getName

      public String getName()
      Description copied from interface: Component
      Get the name of this component.

    • getDescription

      public String getDescription()
      Description copied from interface: Component
      Get the description of this component.

    • isInverse

      public boolean isInverse(Transformer obj)
      Description copied from class: Transformer
      Are these two transformations, inverses of each other? This method is used to optimize a series of transformations where transformations.
      Specified by:
      isInverse in class Transformer

    • inverse

      public Deprojecter inverse()
      Description copied from class: Projecter
      Get the inverse
      Specified by:
      inverse in class Projecter

    • transform

      public void transform(double[] unit, double[] plane)
      Description copied from class: Transformer
      Convert a single point where the output vector is supplied.
      Specified by:
      transform in class Transformer
      Parameters:
      unit - The input vector.
      plane - The output vector, it may be the same as the input vector if the dimensionalities are the same. All transformers are expected to work with aliased inputs and output.

    • tile

      public double[][][] tile(int level, int ix, int iy, int subdiv)

    • show

      public static void show(String prefix, double[] vector)

    • main

      public static void main(String[] args) throws Exception
      Throws:
      Exception

    • straddleable

      public boolean straddleable()
      Description copied from class: Projecter
      Is it possible for a pixel to straddle the valid region.
      Overrides:
      straddleable in class Projecter

    • shadowPoint

      public double[] shadowPoint(double x, double y)
      Description copied from class: Projecter
      Return a shadowpoint for the input location. Shadowpoints are not defined for all projections.
      Overrides:
      shadowPoint in class Projecter

    • straddle

      public boolean straddle(double[][] vertices)
      Description copied from class: Projecter
      Does this pixel go wrap around the standard region of the image? E.g., does it straddle the 180 deg in a Car or Ait projection?
      Overrides:
      straddle in class Projecter

    • straddleComponents

      public double[][][] straddleComponents(double[][] vertices)
      Description copied from class: Projecter
      If this is a straddling pixel, then return the straddle components
      Overrides:
      straddleComponents in class Projecter