Class InterpolatedMolodenskyTransform

All Implemented Interfaces:
Serializable, Parameterized, LenientComparable, org.opengis.referencing.operation.MathTransform
Direct Known Subclasses:
InterpolatedMolodenskyTransform.Inverse, InterpolatedMolodenskyTransform2D

public class InterpolatedMolodenskyTransform extends MolodenskyFormula
Transforms between two geographic CRS by performing geocentric translations interpolated from a grid file, but using Molodensky approximation. This transformation is conceptually defined as a translation in geocentric coordinates as performed by InterpolatedGeocentricTransform, but uses the Molodensy (non-abridged) approximation for performance reasons. Errors are less than 3 centimetres for the "France geocentric interpolation" (ESPG:9655). By comparison, the finest accuracy reported in the grid file for France is 5 centimetres.

Algorithm

This class transforms two- or three- dimensional coordinates from a geographic CRS to another geographic CRS. The changes between source and target coordinates are small (usually less than 400 metres), but vary for every position. Those changes are provided in a datum shift grid, usually loaded from one or two files.

Many datum shift grids like NADCON and NTv2 apply the interpolated translations directly on geographic coordinates. This relatively simple case is handled by InterpolatedTransform. But in the InterpolatedMolodenskyTransform case, the interpolated translations are rather the (MolodenskyFormula.tX, MolodenskyFormula.tY, MolodenskyFormula.tZ) parameters of a Molodensky transformation.

Since:
0.7
Version:
1.0
See Also:
  • Field Details

    • serialVersionUID

      private static final long serialVersionUID
      Serial number for inter-operability with different versions.
      See Also:
    • DESCRIPTOR

      private static final org.opengis.parameter.ParameterDescriptorGroup DESCRIPTOR
      Parameter descriptor to use with the contextual parameters for the forward and inverse transformations. We do not use directly the "France geocentric interpolation" (ESPG:9655) descriptor because this InterpolatedMolodenskyTransform is an approximation of InterpolatedGeocentricTransform and the conventions used by SIS are different than EPSG:9655 ones.
    • INVERSE

      private static final org.opengis.parameter.ParameterDescriptorGroup INVERSE
      Parameter descriptor to use with the contextual parameters for the forward and inverse transformations. We do not use directly the "France geocentric interpolation" (ESPG:9655) descriptor because this InterpolatedMolodenskyTransform is an approximation of InterpolatedGeocentricTransform and the conventions used by SIS are different than EPSG:9655 ones.
    • inverse

      private final InterpolatedMolodenskyTransform inverse
      The inverse of this interpolated Molodensky transform.
      See Also:
  • Constructor Details

    • InterpolatedMolodenskyTransform

      InterpolatedMolodenskyTransform(InterpolatedMolodenskyTransform inverse, org.opengis.referencing.datum.Ellipsoid source, org.opengis.referencing.datum.Ellipsoid target)
      Constructs the inverse of an interpolated Molodensky transform.
      Parameters:
      inverse - the transform for which to create the inverse.
      source - the source ellipsoid of the given inverse transform.
      target - the target ellipsoid of the given inverse transform.
    • InterpolatedMolodenskyTransform

      protected InterpolatedMolodenskyTransform(org.opengis.referencing.datum.Ellipsoid source, boolean isSource3D, org.opengis.referencing.datum.Ellipsoid target, boolean isTarget3D, DatumShiftGrid<javax.measure.quantity.Angle,javax.measure.quantity.Length> grid)
      Creates a transform from the specified parameters. This InterpolatedMolodenskyTransform class expects coordinate values in the following order and units:
      1. longitudes in radians relative to the prime meridian (usually Greenwich),
      2. latitudes in radians,
      3. optionally heights above the ellipsoid, in same units than the source ellipsoid axes.
      For converting geographic coordinates in degrees, InterpolatedMolodenskyTransform instances need to be concatenated with the following affine transforms:
      • Normalization before InterpolatedMolodenskyTransform:
        • Conversion of (λ,φ) from degrees to radians.
      • Denormalization after InterpolatedMolodenskyTransform:
        • Conversion of (λ,φ) from radians to degrees.
      After InterpolatedMolodenskyTransform construction, the full conversion chain including the above affine transforms can be created by DatumShiftTransform.getContextualParameters().completeTransform(factory, this)}.
      Parameters:
      source - the source ellipsoid.
      isSource3D - true if the source coordinates have a height.
      target - the target ellipsoid.
      isTarget3D - true if the target coordinates have a height.
      grid - the grid of datum shifts from source to target datum. The DatumShiftGrid.interpolateInCell(…) method shall compute (ΔX, ΔY, ΔZ) translations from source to target in the unit of source ellipsoid axes.
      See Also:
  • Method Details

    • createGeodeticTransformation

      public static org.opengis.referencing.operation.MathTransform createGeodeticTransformation(org.opengis.referencing.operation.MathTransformFactory factory, org.opengis.referencing.datum.Ellipsoid source, boolean isSource3D, org.opengis.referencing.datum.Ellipsoid target, boolean isTarget3D, DatumShiftGrid<javax.measure.quantity.Angle,javax.measure.quantity.Length> grid) throws org.opengis.util.FactoryException
      Creates a transformation between two geographic CRS. This factory method combines the InterpolatedMolodenskyTransform instance with the steps needed for converting values between degrees to radians. The transform works with input and output coordinates in the following units:
      1. longitudes in degrees relative to the prime meridian (usually Greenwich),
      2. latitudes in degrees,
      3. optionally heights above the ellipsoid, in same units than the source ellipsoids axes.
      Note however that the given grid instance shall expect geographic coordinates (λ,φ) in radians.
      Parameters:
      factory - the factory to use for creating the transform.
      source - the source ellipsoid.
      isSource3D - true if the source coordinates have a height.
      target - the target ellipsoid.
      isTarget3D - true if the target coordinates have a height.
      grid - the grid of datum shifts from source to target datum. The DatumShiftGrid.interpolateInCell(…) method shall compute (ΔX, ΔY, ΔZ) translations from source to target in the unit of source ellipsoid axes.
      Returns:
      the transformation between geographic coordinates in degrees.
      Throws:
      org.opengis.util.FactoryException - if an error occurred while creating a transform.
    • completeParameters

      final void completeParameters(Parameters pg, double semiMinor, javax.measure.Unit<?> unit, double Δf)
      Invoked by constructor and by MolodenskyFormula.getParameterValues() for setting all parameters other than axis lengths.
      Overrides:
      completeParameters in class MolodenskyFormula
      Parameters:
      pg - where to set the parameters.
      semiMinor - the semi minor axis length, in unit of unit.
      unit - the unit of measurement to declare.
      Δf - ignored.
    • transform

      public org.opengis.referencing.operation.Matrix transform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, boolean derivate) throws org.opengis.referencing.operation.TransformException
      Transforms the (λ,φ) or (λ,φ,h) coordinates between two geographic CRS, and optionally returns the derivative at that location.
      Specified by:
      transform in class AbstractMathTransform
      Parameters:
      srcPts - the array containing the source coordinates (cannot be null).
      srcOff - the offset to the point to be transformed in the source array.
      dstPts - the array into which the transformed coordinates is returned. May be the same than srcPts. May be null if only the derivative matrix is desired.
      dstOff - the offset to the location of the transformed point that is stored in the destination array.
      derivate - true for computing the derivative, or false if not needed.
      Returns:
      the matrix of the transform derivative at the given source position, or null if the derivate argument is false.
      Throws:
      org.opengis.referencing.operation.TransformException - if the point cannot be transformed or if a problem occurred while calculating the derivative.
      See Also:
    • transform

      public void transform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, int numPts) throws org.opengis.referencing.operation.TransformException
      Transforms the (λ,φ) or (λ,φ,h) coordinates between two geographic CRS. This method performs the same work than the above transform(…) method, but on an arbitrary number of coordinate tuples and without computing derivative.
      Specified by:
      transform in interface org.opengis.referencing.operation.MathTransform
      Overrides:
      transform in class AbstractMathTransform
      Parameters:
      srcPts - the array containing the source point coordinates.
      srcOff - the offset to the first point to be transformed in the source array.
      dstPts - the array into which the transformed point coordinates are returned. May be the same than srcPts.
      dstOff - the offset to the location of the first transformed point that is stored in the destination array.
      numPts - the number of point objects to be transformed.
      Throws:
      org.opengis.referencing.operation.TransformException - if a point cannot be transformed.
    • inverse

      public org.opengis.referencing.operation.MathTransform inverse()
      Returns the inverse of this interpolated Molodensky transform. The source ellipsoid of the returned transform will be the target ellipsoid of this transform, and conversely.
      Specified by:
      inverse in interface org.opengis.referencing.operation.MathTransform
      Overrides:
      inverse in class AbstractMathTransform
      Returns:
      a transform from the target ellipsoid to the source ellipsoid of this transform.
    • getParameterDescriptors

      @Debug public org.opengis.parameter.ParameterDescriptorGroup getParameterDescriptors()
      Returns a description of the internal parameters of this InterpolatedMolodenskyTransform transform. The returned group contains parameters for the source ellipsoid semi-axis lengths and the differences between source and target ellipsoid parameters.
      Note: this method is mostly for debugging purposes since the isolation of non-linear parameters in this class is highly implementation dependent. Most GIS applications will instead be interested in the contextual parameters.
      Specified by:
      getParameterDescriptors in interface Parameterized
      Overrides:
      getParameterDescriptors in class AbstractMathTransform
      Returns:
      a description of the internal parameters.
      See Also: