org.geotools.referencing.operation.builder

Class MathTransformBuilder

Object

MathTransformBuilder

Direct Known Subclasses:

AdvancedAffineBuilder, BursaWolfTransformBuilder, ProjectiveTransformBuilder, RubberSheetBuilder

public abstract class MathTransformBuilder
extends Object

Provides a basic implementation for math transform builders.

Math transform builders create MathTransform objects for transforming coordinates from a source CRS (Coordinate Reference System) to a target CRS using empirical parameters. Usually, one of those CRS is a geographic or projected one with a well known relationship to the earth. The other CRS is often an engineering or image one tied to some ship. For example a remote sensing image before georectification may be referenced by an image CRS.

Design note: It is technically possible to reference such remote sensing images with a CRS derived from the geographic or projected CRS, where the conversion from base is the math transform computed by this builder. Such approach is advantageous for coordinate operation factory implementations, since they can determine the operation just by inspection of the DerivedCRS instance. However this is conceptually incorrect since DerivedCRS can be related to an other CRS only through conversions, which by definition are accurate up to rounding errors. The operations created by math transform builders are rather transformations, which can't be used for DerivedCRS creation.

The math transform from source CRS to target CRS is calculated by MathTransformBuilder from a set of mapped positions in both CRS.

Subclasses must implement at least the getMinimumPointCount() and computeMathTransform() methods.

Since:

2.4

Author:

Jan Jezek, Martin Desruisseaux

Field Summary

Fields

Modifier and Type	Field and Description
protected MathTransformFactory	mtFactory The factory to use for creating math transform instances.

Constructor Summary

Constructors

Constructor and Description
MathTransformBuilder() Creates a builder with the default factories.
MathTransformBuilder(Hints hints) Creates a builder from the specified hints.

Method Summary

Modifier and Type	Method and Description
protected abstract MathTransform	computeMathTransform() Calculates the math transform immediately.
Class<? extends CoordinateSystem>	getCoordinateSystemType() Returns the required coordinate system type.
int	getDimension() Returns the dimension for source and target CRS.
Statistics	getErrorStatistics() Returns statistics about the errors.
List<MappedPosition>	getMappedPositions() Returns the list of mapped positions.
MathTransform	getMathTransform() Returns the calculated math transform.
abstract int	getMinimumPointCount() Returns the minimum number of points required by this builder.
String	getName() Returns the name for the transformation to be created by this builder.
CoordinateReferenceSystem	getSourceCRS() Returns the coordinate reference system for the source points.
DirectPosition[]	getSourcePoints() Returns the source points.
CoordinateReferenceSystem	getTargetCRS() Returns the coordinate reference system for the target points.
DirectPosition[]	getTargetPoints() Returns the target points.
Transformation	getTransformation() Returns the coordinate operation wrapping the calculated math transform.
void	printPoints(Writer out, Locale locale) Prints a table of all source and target points stored in this builder.
void	setMappedPositions(List<MappedPosition> positions) Set the list of mapped positions.
void	setSourcePoints(DirectPosition[] points) Convenience method setting the source points in mapped positions.
void	setTargetPoints(DirectPosition[] points) Convenience method setting the target points in mapped positions.
String	toString() Returns a string representation of this builder.

Methods inherited from class Object

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

Field Detail

mtFactory

protected final MathTransformFactory mtFactory

The factory to use for creating math transform instances.

Constructor Detail

MathTransformBuilder

public MathTransformBuilder()

Creates a builder with the default factories.

MathTransformBuilder

public MathTransformBuilder(Hints hints)

Creates a builder from the specified hints.

Method Detail

getName

public String getName()

Returns the name for the transformation to be created by this builder.

getMinimumPointCount

public abstract int getMinimumPointCount()

Returns the minimum number of points required by this builder. This minimum depends on the algorithm used. For example affine transform builders require at least 3 points, while similar transform builders requires only 2 points.

getDimension

public int getDimension()

Returns the dimension for source and target CRS. The default value is 2.

getMappedPositions

public List<MappedPosition> getMappedPositions()

Returns the list of mapped positions.

setMappedPositions

public void setMappedPositions(List<MappedPosition> positions)
                        throws IllegalArgumentException,
                               MismatchedDimensionException,
                               MismatchedReferenceSystemException

Set the list of mapped positions.

Throws:

IllegalArgumentException - if the list doesn't have the expected number of points.

MismatchedDimensionException - if some points doesn't have the expected number of dimensions.

MismatchedReferenceSystemException - if CRS is not the same for all points.

getSourcePoints

public DirectPosition[] getSourcePoints()

Returns the source points. This convenience method extracts those points from the mapped positions.

setSourcePoints

public void setSourcePoints(DirectPosition[] points)
                     throws IllegalArgumentException,
                            MismatchedDimensionException,
                            MismatchedReferenceSystemException

Convenience method setting the source points in mapped positions.

Parameters:

points - The source points.

Throws:

IllegalArgumentException - if the list doesn't have the expected number of points.

MismatchedDimensionException - if some points doesn't have the expected number of dimensions.

MismatchedReferenceSystemException - if CRS is not the same for all points.

getTargetPoints

public DirectPosition[] getTargetPoints()

Returns the target points. This convenience method extracts those points from the mapped positions.

setTargetPoints

public void setTargetPoints(DirectPosition[] points)
                     throws IllegalArgumentException,
                            MismatchedDimensionException,
                            MismatchedReferenceSystemException

Convenience method setting the target points in mapped positions.

Parameters:

points - The target points.

Throws:

IllegalArgumentException - if the list doesn't have the expected number of points.

MismatchedDimensionException - if some points doesn't have the expected number of dimensions.

MismatchedReferenceSystemException - if CRS is not the same for all points.

printPoints

public void printPoints(Writer out,
                        Locale locale)
                 throws IOException

Prints a table of all source and target points stored in this builder.

Parameters:

out - The output device where to print all points.

locale - The locale, or null for the default.

Throws:

IOException - if an error occured while printing.

getSourceCRS

public CoordinateReferenceSystem getSourceCRS()
                                       throws FactoryException

Returns the coordinate reference system for the source points. This method determines the CRS as below:

• If at least one source points has a CRS, then this CRS is selected as the source one and returned.
• If no source point has a CRS, then this method creates an engineering CRS using the same coordinate system than the one used by the target CRS.

Throws:

FactoryException - if the CRS can't be created.

getTargetCRS

public CoordinateReferenceSystem getTargetCRS()
                                       throws FactoryException

Returns the coordinate reference system for the target points. This method determines the CRS as below:

• If at least one target points has a CRS, then this CRS is selected as the target one and returned.
• If no target point has a CRS, then this method creates an engineering CRS using the same coordinate system than the one used by the source CRS.

Throws:

FactoryException - if the CRS can't be created.

getCoordinateSystemType

public Class<? extends CoordinateSystem> getCoordinateSystemType()

Returns the required coordinate system type. The default implementation returns CoordinateSystem.class, which means that every kind of coordinate system is legal. Some subclasses will restrict to cartesian CS.

getErrorStatistics

public Statistics getErrorStatistics()
                              throws FactoryException

Returns statistics about the errors. The errors are computed as the distance between source points transformed by the math transform computed by this MathTransformBuilder, and the target points. Use Statistics.rms() for the Root Mean Squared error.

Throws:

FactoryException - If the math transform can't be created or used.

computeMathTransform

protected abstract MathTransform computeMathTransform()
                                               throws FactoryException

Calculates the math transform immediately.

Returns:

Math transform from MappedPosition.

Throws:

FactoryException - if the math transform can't be created.

getMathTransform

public final MathTransform getMathTransform()
                                     throws FactoryException

Returns the calculated math transform. This method the math transform the first time it is requested.

Returns:

Math transform from MappedPosition.

Throws:

FactoryException - if the math transform can't be created.

getTransformation

public Transformation getTransformation()
                                 throws FactoryException

Returns the coordinate operation wrapping the calculated math transform. The positional accuracy will be set to the Root Mean Square (RMS) of the differences between the source points transformed to the target CRS, and the expected target points.

Throws:

FactoryException

toString

public String toString()

Returns a string representation of this builder. The default implementation returns a table containing all source and target points.

Overrides:

toString in class Object