Module org.apache.sis.referencing

Package org.apache.sis.referencing.operation.transform

Class InterpolatedTransform

Object

FormattableObject

AbstractMathTransform

DatumShiftTransform

InterpolatedTransform

All Implemented Interfaces:

Serializable, Parameterized, Lenient­Comparable, Math­Transform

public class InterpolatedTransform
extends DatumShiftTransform

Transforms between two CRS by performing translations interpolated from a grid file. The source and target coordinate reference systems are typically, but not necessarily, two-dimensional geographic CRS. The actual number of dimensions is determined by Datum­Shift­Grid.get­Translation­Dimensions().

This transform is used for example with NADCON and NTv2 datum shift grids.

Input and output coordinates

First, "real world" input coordinates (x,y) are converted to grid coordinates (gridX, gridY), which are zero-based indices in the two-dimensional grid. This conversion is applied by an affine transform before to be passed to the transform methods of this Interpolated­Transform class.

Translation vectors are stored in the datum shift grid at the specified grid indices. If the grid indices are non-integer values, then the translations are interpolated using a bilinear interpolation. If the grid indices are outside the grid domain ([0 … width-1] × [0 … height-1] where width and height are the number of columns and rows in the grid), then the translations are extrapolated. The translation is finally added to the input coordinates.

The input and output coordinates can have any number of dimensions, provided that they are the same than the number of translation dimensions. However, current implementation uses only the two first dimensions for interpolations in the grid.

Since:

0.7

See Also:

• Datum­Shift­Grid
• Localization­Grid­Builder
• Serialized Form

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Interpolated­Transform(Datum­Shift­Grid<T,T> grid)	Creates a transform for the given interpolation grid.

Method Summary

Modifier and Type	Method	Description
protected int	compute­Hash­Code()	Computes a hash value for this transform.
static <T extends Quantity<T>> Math­Transform	create­Geodetic­Transformation(Math­Transform­Factory factory, Datum­Shift­Grid<T,T> grid)	Creates a transformation between two geodetic CRS.
boolean	equals(Object object, Comparison­Mode mode)	Compares the specified object with this math transform for equality.
final Datum­Shift­Grid<?,?>	get­Shift­Grid()	Returns the grid of datum shifts specified at construction time.
final int	get­Source­Dimensions()	Returns the number of input dimensions.
final int	get­Target­Dimensions()	Returns the number of target dimensions.
Math­Transform	inverse()	Returns the inverse of this interpolated transform.
Matrix	transform(double[] src­Pts, int src­Off, double[] dst­Pts, int dst­Off, boolean derivate)	Applies the datum shift on a coordinate tuple and optionally returns the derivative at that location.
void	transform(double[] src­Pts, int src­Off, double[] dst­Pts, int dst­Off, int num­Pts)	Transforms an arbitrary number of coordinate tuples.

Methods inherited from class DatumShiftTransform

get­Contextual­Parameters, get­Parameter­Values

Methods inherited from class AbstractMathTransform

derivative, equals, format­To, get­Domain, get­Parameter­Descriptors, 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

Constructor Details

InterpolatedTransform

protected InterpolatedTransform(DatumShiftGrid<T,T> grid)
                         throws NoninvertibleMatrixException

Creates a transform for the given interpolation grid. This Interpolated­Transform class works with coordinate values in units of grid cell For example, input coordinates (4,5) is the position of the center of the cell at grid index (4,5). The output units are the same than the input units.

For converting geodetic coordinates, Interpolated­Transform instances need to be concatenated with the following affine transforms:

• Normalization before Interpolated­Transform for converting the geodetic coordinates into grid coordinates.
• Denormalization after Interpolated­Transform for converting grid coordinates into geodetic coordinates.

After Interpolated­Transform construction, the full conversion chain including the above affine transforms can be created by Datum­Shift­Transform.get­Contextual­Parameters().complete­Transform(factory, this)}.

Type Parameters:

T - dimension of the coordinate tuples and the translation unit.

Parameters:

grid - the grid of datum shifts from source to target datum.

Throws:

Noninvertible­Matrix­Exception - if the conversion from geodetic coordinates to grid indices cannot be inverted.

See Also:

• create­Geodetic­Transformation(Math­Transform­Factory, Datum­Shift­Grid)

Method Details

createGeodeticTransformation

public static <T extends Quantity<T>> MathTransform createGeodeticTransformation(MathTransformFactory factory,
 DatumShiftGrid<T,T> grid)
                                                                          throws FactoryException

Creates a transformation between two geodetic CRS. This factory method combines the Interpolated­Transform instance with the steps needed for converting values between geodetic and grid coordinates.

Unit of measurement

The unit of measurement is determined by Datum­Shift­Grid.get­Coordinate­Unit():

• If the datum shift unit is angular, then the transform will work with input and output coordinates in degrees of angle.
• If the datum shift unit is linear, then the transform will work with input and output coordinates in metres.
• If the datum shift unit is temporal, then the transform will work with input and output coordinates in seconds.
• Generally for all units other than angular, the transform will work with input and output coordinates in the unit given by Unit.get­System­Unit().

Type Parameters:

T - dimension of the coordinate tuples and the translation unit.

Parameters:

factory - the factory to use for creating the transform.

grid - the grid of datum shifts from source to target datum. The Datum­Shift­Grid.interpolate­In­Cell(…) method shall compute translations from source to target as ratio of offsets divided by cell sizes.

Returns:

the transformation between geodetic coordinates.

Throws:

Factory­Exception - if an error occurred while creating a transform.

getShiftGrid

public final DatumShiftGrid<?,?> getShiftGrid()

Returns the grid of datum shifts specified at construction time.

Returns:

the grid of datum shifts from source to target datum.

Since:

1.1

getSourceDimensions

public final int getSourceDimensions()

Returns the number of input dimensions. This fixed to Datum­Shift­Grid.get­Translation­Dimensions().

Specified by:

get­Source­Dimensions in interface Math­Transform

Specified by:

get­Source­Dimensions in class Abstract­Math­Transform

Returns:

the dimension of input points.

See Also:

• Default­Operation­Method.get­Source­Dimensions()

getTargetDimensions

public final int getTargetDimensions()

Returns the number of target dimensions. This fixed to Datum­Shift­Grid.get­Translation­Dimensions().

Specified by:

get­Target­Dimensions in interface Math­Transform

Specified by:

get­Target­Dimensions in class Abstract­Math­Transform

Returns:

the dimension of output points.

See Also:

• Default­Operation­Method.get­Target­Dimensions()

transform

public Matrix transform(double[] srcPts,
 int srcOff,
 double[] dstPts,
 int dstOff,
 boolean derivate)
                 throws TransformException

Applies the datum shift on a coordinate tuple 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:

Transform­Exception - if the point cannot 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 an arbitrary number of coordinate tuples.

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 cannot be transformed.

inverse

public MathTransform inverse()

Returns the inverse of this interpolated 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.

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)