Class MolodenskyTransform
Object
FormattableObject
AbstractMathTransform
DatumShiftTransform
MolodenskyTransform
- All Implemented Interfaces:
Serializable,Parameterized,LenientComparable,MathTransform
Two- or three-dimensional datum shift using the (potentially abridged) Molodensky transformation.
The Molodensky transformation (EPSG:9604) and the abridged Molodensky transformation (EPSG:9605)
transform geographic points from one geographic coordinate reference system to another (a datum shift).
The Molodensky formulas are approximations of Geocentric translation (geographic domain)
transformations (EPSG:1035 and 9603), but performed directly on geographic coordinates without
Geographic/Geocentric conversions.
MolodenskyTransforms works conceptually on three-dimensional coordinates, but the ellipsoidal height
can be omitted resulting in two-dimensional coordinates. No dimension other than 2 or 3 are allowed.
- If the height is omitted from the input coordinates (
isSource3D=false), then the source dimensions is 2 and the height is assumed to be zero. - If the height is omitted from the output coordinates (
isTarget3D=false), then the target dimensions is 2 and the computed height (typically non-zero even if the input height was zero) is lost.
- longitudes (λ) relative to the prime meridian (usually Greenwich),
- latitudes (φ),
- optionally heights above the ellipsoid (h).
MathTransform has been created:
MolodenskyTransforminstances created directly by the constructor work with angular values in radians.- Transforms created by the
createGeodeticTransformation(…)static method work with angular values in degrees and heights in the same units than the source ellipsoid axes (usually metres).
Comparison of Molodensky and geocentric translation
Compared to the "Geocentric translation (geographic domain)" method, the Molodensky method has errors usually within a few centimetres. The Abridged Molodensky method has more noticeable errors, of a few tenths of centimetres.Another difference between Molodensky and geocentric translation methods is their behavior when crossing the anti-meridian. If a datum shift causes a longitude to cross the anti-meridian (e.g. 179.999° become 180.001°), the Molodensky method will keep 180.001° as-is while the geocentric translation method will wrap the longitude to -179.999°. Such wrap-around behavior may or may not be desired, depending on the applications.
- Since:
- 0.7
- See Also:
Defined in the sis-referencing module
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Nested Class Summary
Nested classes/interfaces inherited from class AbstractMathTransform
AbstractMathTransform.Inverse -
Field Summary
FieldsModifier and TypeFieldDescriptionprotected final doubleThe square of eccentricity of the source ellipsoid.protected final doubleSemi-major axis length (a) of the source ellipsoid.protected final doubleShift along the geocentric X axis (toward prime meridian) in units of the semi-major axis of the source ellipsoid.protected final doubleShift along the geocentric Y axis (toward 90°E) in units of the semi-major axis of the source ellipsoid.protected final doubleShift along the geocentric Z axis (toward north pole) in units of the semi-major axis of the source ellipsoid. -
Constructor Summary
ConstructorsConstructorDescriptionMolodenskyTransform(Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, double tX, double tY, double tZ, boolean isAbridged) Creates a Molodensky transform from the specified parameters. -
Method Summary
Modifier and TypeMethodDescriptionprotected intComputes a hash value for this transform.static MathTransformcreateGeodeticTransformation(MathTransformFactory factory, Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, double tX, double tY, double tZ, boolean isAbridged) Creates a transformation between two from geographic CRS.booleanequals(Object object, ComparisonMode mode) Compares the specified object with this math transform for equality.Returns a description of the internal parameters of thisMolodenskyTransformtransform.Returns a copy of internal parameter values of this transform.final intGets the dimension of input points.final intGets the dimension of output points.inverse()Returns the inverse of this Molodensky transform.booleanReturnstrueif this transform is the identity one.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.voidtransform(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
getContextualParametersMethods inherited from class AbstractMathTransform
derivative, equals, formatTo, getDomain, hashCode, transform, transform, transform, transform, tryConcatenateMethods inherited from class FormattableObject
print, toString, toString, toWKTMethods inherited from class Object
clone, finalize, getClass, notify, notifyAll, wait, wait, waitMethods inherited from interface MathTransform
toWKT
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Field Details
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tX
protected final double tXShift along the geocentric X axis (toward prime meridian) in units of the semi-major axis of the source ellipsoid.- See Also:
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tY
protected final double tYShift along the geocentric Y axis (toward 90°E) in units of the semi-major axis of the source ellipsoid.- See Also:
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tZ
protected final double tZShift along the geocentric Z axis (toward north pole) in units of the semi-major axis of the source ellipsoid.- See Also:
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semiMajor
protected final double semiMajorSemi-major axis length (a) of the source ellipsoid. -
eccentricitySquared
protected final double eccentricitySquaredThe 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.
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Constructor Details
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MolodenskyTransform
public MolodenskyTransform(Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, double tX, double tY, double tZ, boolean isAbridged) Creates a Molodensky transform from the specified parameters. ThisMolodenskyTransformclass expects coordinate values in the following order and units:- longitudes in radians relative to the prime meridian (usually Greenwich),
- latitudes in radians,
- optionally heights above the ellipsoid, in same units than the source ellipsoid axes.
MolodenskyTransforminstances need to be concatenated with the following affine transforms:- Normalization before
MolodenskyTransform:- Conversion of (λ,φ) from degrees to radians.
- Denormalization after
MolodenskyTransform:- Conversion of (λ,φ) from radians to degrees.
MolodenskyTransformconstruction, the full conversion chain including the above affine transforms can be created byDatumShiftTransform.getContextualParameters().completeTransform(factory, this)}.- Parameters:
source- the source ellipsoid.isSource3D-trueif the source coordinates have a height.target- the target ellipsoid.isTarget3D-trueif the target coordinates have a height.tX- the geocentric X translation in same units than the source ellipsoid axes.tY- the geocentric Y translation in same units than the source ellipsoid axes.tZ- the geocentric Z translation in same units than the source ellipsoid axes.isAbridged-truefor the abridged formula, orfalsefor the complete one.- See Also:
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Method Details
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createGeodeticTransformation
public static MathTransform createGeodeticTransformation(MathTransformFactory factory, Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, double tX, double tY, double tZ, boolean isAbridged) throws FactoryException Creates a transformation between two from geographic CRS. This factory method combines theMolodenskyTransforminstance with the steps needed for converting values between degrees to radians. The transform works with input and output coordinates in the following units:- longitudes in degrees relative to the prime meridian (usually Greenwich),
- latitudes in degrees,
- optionally heights above the ellipsoid, in same units than the source ellipsoids axes.
- Parameters:
factory- the factory to use for creating the transform.source- the source ellipsoid.isSource3D-trueif the source coordinates have a height.target- the target ellipsoid.isTarget3D-trueif the target coordinates have a height.tX- the geocentric X translation in same units than the source ellipsoid axes.tY- the geocentric Y translation in same units than the source ellipsoid axes.tZ- the geocentric Z translation in same units than the source ellipsoid axes.isAbridged-truefor the abridged formula, orfalsefor the complete one.- Returns:
- the transformation between geographic coordinates in degrees.
- Throws:
FactoryException- if an error occurred while creating a transform.
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isIdentity
public boolean isIdentity()Returnstrueif this transform is the identity one. Molodensky transform is considered identity (minus rounding errors) if:- the X,Y,Z shift are zero,
- difference between semi-major axis lengths (Δa) is zero,
- difference between flattening factors (Δf) is zero,
- the input and output dimension are the same.
- Specified by:
isIdentityin interfaceMathTransform- Overrides:
isIdentityin classAbstractMathTransform- Returns:
trueif this transform is the identity transform.
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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:
transformin classAbstractMathTransform- Parameters:
srcPts- the array containing the source coordinates (cannot benull).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 thansrcPts. May benullif only the derivative matrix is desired.dstOff- the offset to the location of the transformed point that is stored in the destination array.derivate-truefor computing the derivative, orfalseif not needed.- Returns:
- the matrix of the transform derivative at the given source position,
or
nullif thederivateargument isfalse. - Throws:
TransformException- if the point cannot be transformed or if a problem occurred while calculating the derivative.- See Also:
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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 transformation thantransform(double[], int, double[], int, boolean), but the formulas are repeated here for performance reasons.- Specified by:
transformin interfaceMathTransform- Overrides:
transformin classAbstractMathTransform- 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 thansrcPts.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.
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inverse
Returns the inverse of this Molodensky transform. The source ellipsoid of the returned transform will be the target ellipsoid of this transform, and conversely.- Specified by:
inversein interfaceMathTransform- Overrides:
inversein classAbstractMathTransform- Returns:
- a Molodensky transform from the target ellipsoid to the source ellipsoid of this transform.
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getParameterDescriptors
Returns a description of the internal parameters of thisMolodenskyTransformtransform. The returned group contains parameter descriptors for the number of dimensions and the eccentricity.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:
getParameterDescriptorsin interfaceParameterized- Overrides:
getParameterDescriptorsin classAbstractMathTransform- Returns:
- a description of the internal parameters.
- See Also:
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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:
getParameterValuesin interfaceParameterized- Overrides:
getParameterValuesin classDatumShiftTransform- Returns:
- a copy of the internal parameter values for this transform.
- See Also:
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getSourceDimensions
public final int getSourceDimensions()Gets the dimension of input points.- Specified by:
getSourceDimensionsin interfaceMathTransform- Specified by:
getSourceDimensionsin classAbstractMathTransform- Returns:
- the input dimension, which is 2 or 3.
- See Also:
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getTargetDimensions
public final int getTargetDimensions()Gets the dimension of output points.- Specified by:
getTargetDimensionsin interfaceMathTransform- Specified by:
getTargetDimensionsin classAbstractMathTransform- Returns:
- the output dimension, which is 2 or 3.
- See Also:
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computeHashCode
protected int computeHashCode()Computes a hash value for this transform. This method is invoked byAbstractMathTransform.hashCode()when first needed.- Overrides:
computeHashCodein classDatumShiftTransform- Returns:
- the hash code value. This value may change between different execution of the Apache SIS library.
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equals
Compares the specified object with this math transform for equality.- Specified by:
equalsin interfaceLenientComparable- Overrides:
equalsin classDatumShiftTransform- Parameters:
object- the object to compare with this transform.mode- the strictness level of the comparison. Default toSTRICT.- Returns:
trueif the given object is considered equals to this math transform.- See Also:
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