org.opengis.referencing.operation

Interface MathTransformFactory

All Superinterfaces:

Factory

All Known Implementing Classes:

DefaultMathTransformFactory

@UML(identifier="CT_MathTransformFactory",
     specification=OGC_01009)
public interface MathTransformFactory
extends Factory

Low level factory for creating math transforms. Many high level GIS applications will never need to use this factory directly; they can use a coordinate operation factory instead. However, the MathTransformFactory interface can be used directly by applications that wish to transform other types of coordinates (e.g. color coordinates, or image pixel coordinates).

A math transform is an object that actually does the work of applying formulae to coordinate values. The math transform does not know or care how the coordinates relate to positions in the real world. This lack of semantics makes implementing MathTransformFactory significantly easier than it would be otherwise.

For example the affine transform applies a matrix to the coordinates without knowing how what it is doing relates to the real world. So if the matrix scales Z values by a factor of 1000, then it could be converting meters into millimeters, or it could be converting kilometers into meters.

Because math transforms have low semantic value (but high mathematical value), programmers who do not have much knowledge of how GIS applications use coordinate systems, or how those coordinate systems relate to the real world can implement MathTransformFactory. The low semantic content of math transforms also means that they will be useful in applications that have nothing to do with GIS coordinates. For example, a math transform could be used to map color coordinates between different color spaces, such as converting (red, green, blue) colors into (hue, light, saturation) colors.

Since a math transform does not know what its source and target coordinate systems mean, it is not necessary or desirable for a math transform object to keep information on its source and target coordinate systems.

Since:

GeoAPI 1.0

Author:

Martin Desruisseaux (IRD)

See Also:

Projection transform list on RemoteSensing.org

Method Summary

Modifier and Type	Method and Description
MathTransform	createAffineTransform(Matrix matrix) Creates an affine transform from a matrix.
MathTransform	createBaseToDerived(CoordinateReferenceSystem baseCRS, ParameterValueGroup parameters, CoordinateSystem derivedCS) Creates a parameterized transform from a base CRS to a derived CS.
MathTransform	createConcatenatedTransform(MathTransform transform1, MathTransform transform2) Creates a transform by concatenating two existing transforms.
MathTransform	createFromWKT(String wkt) Creates a math transform object from a string.
MathTransform	createFromXML(String xml) Creates a math transform object from a XML string.
MathTransform	createParameterizedTransform(ParameterValueGroup parameters) Creates a transform from a group of parameters.
MathTransform	createPassThroughTransform(int firstAffectedOrdinate, MathTransform subTransform, int numTrailingOrdinates) Creates a transform which passes through a subset of ordinates to another transform.
Set<OperationMethod>	getAvailableMethods(Class<? extends Operation> type) Returns a set of available methods for math transforms.
ParameterValueGroup	getDefaultParameters(String method) Returns the default parameter values for a math transform using the given method.
OperationMethod	getLastMethodUsed() Returns the operation method used for the latest call to createParameterizedTransform, or null if not applicable.

Methods inherited from interface Factory

getVendor

Method Detail

getAvailableMethods

@Extension
Set<OperationMethod> getAvailableMethods(Class<? extends Operation> type)

Returns a set of available methods for math transforms. For each element in this set, the operation method name must be known to the getDefaultParameters(java.lang.String) method in this factory. The set of available methods is implementation dependent.

Parameters:

type - Operation.class for fetching all operation methods, or Projection.class for fetching only map projection methods.

Returns:

All math transform methods available in this factory.

See Also:

getDefaultParameters(java.lang.String), createParameterizedTransform(org.opengis.parameter.ParameterValueGroup)

getLastMethodUsed

@Extension
OperationMethod getLastMethodUsed()

Returns the operation method used for the latest call to createParameterizedTransform, or null if not applicable.

Implementors should document how their implementation behave in a multi-threads environment. For example some implementations use thread local variables, while other can choose to returns null in all cases since this method is optional.

Note that this method may apply as well to convenience methods that delegate their work to createParameterizedTransform, like createBaseToDerived.

Returns:

The last method used, or null if unknown of unsupported.

Since:

GeoAPI 2.1

getDefaultParameters

@Extension
ParameterValueGroup getDefaultParameters(String method)
                                             throws NoSuchIdentifierException

Returns the default parameter values for a math transform using the given method. The method argument is the name of any operation method returned by getAvailableMethods(Operation.class). A typical example is "Transverse_Mercator" ).

The parameter group name shall be the method name, or an alias to be understood by createParameterizedTransform(parameters). This method creates new parameter instances at every call. Parameters are intented to be modified by the user before to be given to the above-cited createParameterizedTransform method.

Parameters:

method - The case insensitive name of the method to search for.

Returns:

The default parameter values.

Throws:

NoSuchIdentifierException - if there is no transform registered for the specified method.

See Also:

getAvailableMethods(java.lang.Class<? extends org.opengis.referencing.operation.Operation>), createParameterizedTransform(org.opengis.parameter.ParameterValueGroup)

createBaseToDerived

@Extension
MathTransform createBaseToDerived(CoordinateReferenceSystem baseCRS,
                                             ParameterValueGroup parameters,
                                             CoordinateSystem derivedCS)
                                      throws NoSuchIdentifierException,
                                             FactoryException

Creates a parameterized transform from a base CRS to a derived CS. This convenience method concatenates the parameterized transform with any other transform required for performing units changes and ordinates swapping, as described in the note on cartographic projections.

In addition, implementations are encouraged to infer the "semi_major" and "semi_minor" parameter values from the ellipsoid, if they are not explicitly given.

Parameters:

baseCRS - The source coordinate reference system.

parameters - The parameter values for the transform.

derivedCS - The target coordinate system.

Returns:

The parameterized transform.

Throws:

NoSuchIdentifierException - if there is no transform registered for the method.

FactoryException - if the object creation failed. This exception is thrown if some required parameter has not been supplied, or has illegal value.

Since:

GeoAPI 2.1

createParameterizedTransform

@UML(identifier="createParameterizedTransform",
     obligation=MANDATORY,
     specification=OGC_01009)
MathTransform createParameterizedTransform(ParameterValueGroup parameters)
                                                                                                                                             throws NoSuchIdentifierException,
                                                                                                                                                    FactoryException

Creates a transform from a group of parameters. The method name is inferred from the parameter group name. Example:

 ParameterValueGroup p = factory.getDefaultParameters("Transverse_Mercator");
 p.parameter("semi_major").setValue(6378137.000);
 p.parameter("semi_minor").setValue(6356752.314);
 MathTransform mt = factory.createParameterizedTransform(p);
 

Note on cartographic projections:

Cartographic projection transforms are used by projected coordinate reference systems to map geographic coordinates (e.g. longitude and latitude) into (x,y) coordinates. These (x,y) coordinates can be imagined to lie on a plane, such as a paper map or a screen. All cartographic projection transforms created through this method will have the following properties:

• Converts from (longitude,latitude) coordinates to (x,y).
• All angles are assumed to be degrees, and all distances are assumed to be meters.
• The domain should be a subset of {[-180,180)×(-90,90)}.

Although all cartographic projection transforms must have the properties listed above, many projected coordinate reference systems have different properties. For example, in Europe some projected CRSs use grads instead of degrees, and often the base geographic CRS is (latitude, longitude) instead of (longitude, latitude). This means that the cartographic projected transform is often used as a single step in a series of transforms, where the other steps change units and swap ordinates.

Parameters:

parameters - The parameter values.

Returns:

The parameterized transform.

Throws:

NoSuchIdentifierException - if there is no transform registered for the method.

FactoryException - if the object creation failed. This exception is thrown if some required parameter has not been supplied, or has illegal value.

See Also:

getDefaultParameters(java.lang.String), getAvailableMethods(java.lang.Class<? extends org.opengis.referencing.operation.Operation>)

createAffineTransform

@UML(identifier="createAffineTransform",
     obligation=MANDATORY,
     specification=OGC_01009)
MathTransform createAffineTransform(Matrix matrix)
                                                                                                                               throws FactoryException

Creates an affine transform from a matrix. If the transform's input dimension is M, and output dimension is N, then the matrix will have size [N+1][M+1]. The +1 in the matrix dimensions allows the matrix to do a shift, as well as a rotation. The [M][j] element of the matrix will be the j'th ordinate of the moved origin. The [i][N] element of the matrix will be 0 for i less than M, and 1 for i equals M.

Parameters:

matrix - The matrix used to define the affine transform.

Returns:

The affine transform.

Throws:

FactoryException - if the object creation failed.

createConcatenatedTransform

@UML(identifier="createConcatenatedTransform",
     obligation=MANDATORY,
     specification=OGC_01009)
MathTransform createConcatenatedTransform(MathTransform transform1,
                                                                                                                                                  MathTransform transform2)
                                                                                                                                           throws FactoryException

Creates a transform by concatenating two existing transforms. A concatenated transform acts in the same way as applying two transforms, one after the other.

The dimension of the output space of the first transform must match the dimension of the input space in the second transform. If you wish to concatenate more than two transforms, then you can repeatedly use this method.

Parameters:

transform1 - The first transform to apply to points.

transform2 - The second transform to apply to points.

Returns:

The concatenated transform.

Throws:

FactoryException - if the object creation failed.

createPassThroughTransform

@UML(identifier="createPassThroughTransform",
     obligation=MANDATORY,
     specification=OGC_01009)
MathTransform createPassThroughTransform(int firstAffectedOrdinate,
                                                                                                                                                MathTransform subTransform,
                                                                                                                                                int numTrailingOrdinates)
                                                                                                                                         throws FactoryException

Creates a transform which passes through a subset of ordinates to another transform. This allows transforms to operate on a subset of ordinates. For example giving (latitude, longitude, height) coordinates, a pass through transform can convert the height values from meters to feet without affecting the (latitude, longitude) values.

Parameters:

firstAffectedOrdinate - The lowest index of the affected ordinates.

subTransform - Transform to use for affected ordinates.

numTrailingOrdinates - Number of trailing ordinates to pass through. Affected ordinates will range from firstAffectedOrdinate inclusive to dimTarget-numTrailingOrdinates exclusive.

Returns:

A pass through transform with the following dimensions:

 Source: firstAffectedOrdinate + subTransform.getDimSource() + numTrailingOrdinates
 Target: firstAffectedOrdinate + subTransform.getDimTarget() + numTrailingOrdinates

Throws:

FactoryException - if the object creation failed.

createFromXML

@UML(identifier="createFromXML",
     obligation=MANDATORY,
     specification=OGC_01009)
MathTransform createFromXML(String xml)
                                                                                                               throws FactoryException

Creates a math transform object from a XML string.

Parameters:

xml - Math transform encoded in XML format.

Returns:

The math transform (never null).

Throws:

FactoryException - if the object creation failed.

createFromWKT

@UML(identifier="createFromWKT",
     obligation=MANDATORY,
     specification=OGC_01009)
MathTransform createFromWKT(String wkt)
                                                                                                               throws FactoryException

Creates a math transform object from a string. The definition for WKT is shown using Extended Backus Naur Form (EBNF).

Parameters:

wkt - Math transform encoded in Well-Known Text format.

Returns:

The math transform (never null).

Throws:

FactoryException - if the Well-Known Text can't be parsed, or if the math transform creation failed from some other reason.