org.apache.sis.referencing.operation.transform

Class InterpolatedMolodenskyTransform

Object

FormattableObject

AbstractMathTransform

DatumShiftTransform

InterpolatedMolodenskyTransform

All Implemented Interfaces:

Serializable, Parameterized, LenientComparable, MathTransform

public class InterpolatedMolodenskyTransform
extends DatumShiftTransform

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 (tX, tY, tZ) parameters of a Molodensky transformation.

Since:

0.7

See Also:

Interpolated­Geocentric­Transform, Serialized Form

Defined in the sis-referencing module

Field Summary

Fields

Modifier and Type	Field and Description
protected double	eccentricitySquared The square of eccentricity of the source ellipsoid.
protected double	semiMajor Semi-major axis length (a) of the source ellipsoid.
protected double	tX Shift along the geocentric X axis (toward prime meridian) in units of the semi-major axis of the source ellipsoid.
protected double	tY Shift along the geocentric Y axis (toward 90°E) in units of the semi-major axis of the source ellipsoid.
protected double	tZ Shift along the geocentric Z axis (toward north pole) in units of the semi-major axis of the source ellipsoid.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	InterpolatedMolodenskyTransform(Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, DatumShiftGrid<Angle,Length> grid) Creates a transform from the specified parameters.

Method Summary

Modifier and Type	Method and Description
protected int	computeHashCode() Computes a hash value for this transform.
static MathTransform	createGeodeticTransformation(MathTransformFactory factory, Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, DatumShiftGrid<Angle,Length> grid) Creates a transformation between two geographic CRS.
boolean	equals(Object object, ComparisonMode mode) Compares the specified object with this math transform for equality.
ParameterDescriptorGroup	getParameterDescriptors() Returns a description of the internal parameters of this Interpolated­Molodensky­Transform transform.
ParameterValueGroup	getParameterValues() Returns a copy of internal parameter values of this transform.
int	getSourceDimensions() Gets the dimension of input points.
int	getTargetDimensions() Gets the dimension of output points.
MathTransform	inverse() Returns the inverse of this interpolated Molodensky transform.
Matrix	transform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, boolean derivate) Transforms the (λ,φ) or (λ,φ,h) coordinates between two geographic CRS, and optionally returns the derivative at that location.
void	transform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, int numPts) Transforms the (λ,φ) or (λ,φ,h) coordinates between two geographic CRS.

Methods inherited from class DatumShiftTransform

get­Contextual­Parameters

Methods inherited from class AbstractMathTransform

derivative, equals, format­To, hash­Code, is­Identity, transform, transform, transform, transform, try­Concatenate

Methods inherited from class FormattableObject

print, to­String, to­String, to­WKT

Methods inherited from class Object

clone, finalize, get­Class, notify, notify­All, wait, wait, wait

Methods inherited from interface MathTransform

to­WKT

Field Detail

tX

protected final double tX

Shift along the geocentric X axis (toward prime meridian) in units of the semi-major axis of the source ellipsoid.

See Also:

Bursa­Wolf­Parameters.t­X

tY

protected final double tY

Shift along the geocentric Y axis (toward 90°E) in units of the semi-major axis of the source ellipsoid.

See Also:

Bursa­Wolf­Parameters.t­Y

tZ

protected final double tZ

Shift along the geocentric Z axis (toward north pole) in units of the semi-major axis of the source ellipsoid.

See Also:

Bursa­Wolf­Parameters.t­Z

semiMajor

protected final double semiMajor

Semi-major axis length (a) of the source ellipsoid.

eccentricitySquared

protected final double eccentricitySquared

The square of eccentricity of the source ellipsoid. This can be computed by ℯ² = (a²-b²)/a² where a is the semi-major axis length and b is the semi-minor axis length.

See Also:

Default­Ellipsoid.get­Eccentricity­Squared()

Constructor Detail

InterpolatedMolodenskyTransform

protected InterpolatedMolodenskyTransform(Ellipsoid source,
                                          boolean isSource3D,
                                          Ellipsoid target,
                                          boolean isTarget3D,
                                          DatumShiftGrid<Angle,Length> grid)

Creates a transform from the specified parameters. This Interpolated­Molodensky­Transform class expects ordinate 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:

create­Geodetic­Transformation(Math­Transform­Factory, Ellipsoid, boolean, Ellipsoid, boolean, Datum­Shift­Grid)

Method Detail

createGeodeticTransformation

public static MathTransform createGeodeticTransformation(MathTransformFactory factory,
                                                         Ellipsoid source,
                                                         boolean isSource3D,
                                                         Ellipsoid target,
                                                         boolean isTarget3D,
                                                         DatumShiftGrid<Angle,Length> grid)
                                                  throws 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:

Factory­Exception - if an error occurred while creating a transform.

transform

public Matrix transform(double[] srcPts,
                        int srcOff,
                        double[] dstPts,
                        int dstOff,
                        boolean derivate)
                 throws 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 coordinate (can not be null).

src­Off - the offset to the point to be transformed in the source array.

dst­Pts - the array into which the transformed coordinate 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:

Transform­Exception - if the point can not be transformed or if a problem occurred while calculating the derivative.

See Also:

Abstract­Math­Transform.derivative(Direct­Position), Abstract­Math­Transform.transform(Direct­Position, Direct­Position), Math­Transforms.derivative­And­Transform(Math­Transform, double[], int, double[], int)

transform

public void transform(double[] srcPts,
                      int srcOff,
                      double[] dstPts,
                      int dstOff,
                      int numPts)
               throws 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 amount of coordinates and without computing derivative.

Specified by:

transform in interface 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:

Transform­Exception - if a point can not be transformed.

inverse

public 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 Math­Transform

Overrides:

inverse in class Abstract­Math­Transform

Returns:

a transform from the target ellipsoid to the source ellipsoid of this transform.

getParameterDescriptors

@Debug
public 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:

Default­Operation­Method.get­Parameters()

getParameterValues

@Debug
public ParameterValueGroup getParameterValues()

Returns a copy of internal parameter values of this 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:

get­Parameter­Values in interface Parameterized

Overrides:

get­Parameter­Values in class Datum­Shift­Transform

Returns:

a copy of the internal parameter values for this transform.

See Also:

Abstract­Math­Transform.get­Contextual­Parameters(), Abstract­Single­Operation.get­Parameter­Values()

getSourceDimensions

public final int getSourceDimensions()

Gets the dimension of input points.

Specified by:

get­Source­Dimensions in interface Math­Transform

Specified by:

get­Source­Dimensions in class Abstract­Math­Transform

Returns:

the input dimension, which is 2 or 3.

See Also:

Default­Operation­Method.get­Source­Dimensions()

getTargetDimensions

public final int getTargetDimensions()

Gets the dimension of output points.

Specified by:

get­Target­Dimensions in interface Math­Transform

Specified by:

get­Target­Dimensions in class Abstract­Math­Transform

Returns:

the output dimension, which is 2 or 3.

See Also:

Default­Operation­Method.get­Target­Dimensions()

computeHashCode

protected int computeHashCode()

Computes a hash value for this transform. This method is invoked by Abstract­Math­Transform.hash­Code() when first needed.

Overrides:

compute­Hash­Code in class Datum­Shift­Transform

Returns:

the hash code value. This value may change between different execution of the Apache SIS library.

equals

public boolean equals(Object object,
                      ComparisonMode mode)

Compares the specified object with this math transform for equality.

Specified by:

equals in interface Lenient­Comparable

Overrides:

equals in class Datum­Shift­Transform

Parameters:

object - the object to compare with this transform.

mode - the strictness level of the comparison. Default to STRICT.

Returns:

true if the given object is considered equals to this math transform.

See Also:

Utilities.deep­Equals(Object, Object, Comparison­Mode)