Module org.apache.sis.referencing
Class EllipsoidToCentricTransform
Object
FormattableObject
AbstractMathTransform
EllipsoidToCentricTransform
- All Implemented Interfaces:
Serializable,Parameterized,LenientComparable,MathTransform
Transform from two- or three- dimensional ellipsoidal coordinates to (geo)centric coordinates.
This transform is usually (but not necessarily) part of a conversion from
geographic to Cartesian
geocentric coordinates.
Each input coordinates is expected to contain:
- longitude (λ) relative to the prime meridian (usually Greenwich),
- latitude (φ),
- optionally height above the ellipsoid (h).
- In the Cartesian case:
- distance from Earth center on the X axis (toward the intersection of prime meridian and equator),
- distance from Earth center on the Y axis (toward the intersection of 90°E meridian and equator),
- distance from Earth center on the Z axis (toward North pole).
MathTransform has been created:
EllipsoidToCentricTransforminstances created directly by the constructor expect (λ,φ) values in radians and compute (X,Y,Z) values in units of an ellipsoid having a semi-major axis length of 1.- Transforms created by the
createGeodeticConversion(…)static method expect (λ,φ) values in degrees and compute (X,Y,Z) values in units of the ellipsoid axes (usually metres).
- Since:
- 0.7
- See Also:
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic enumWhether the output coordinate system is Cartesian or Spherical. -
Field Summary
FieldsModifier and TypeFieldDescriptionprotected final doubleThe square of eccentricity: ℯ² = (a²-b²)/a² where a is the semi-major axis length and b is the semi-minor axis length. -
Constructor Summary
ConstructorsConstructorDescriptionEllipsoidToCentricTransform(double semiMajor, double semiMinor, Unit<Length> unit, boolean withHeight, EllipsoidToCentricTransform.TargetType target) Creates a transform from angles in radians on ellipsoid having a semi-major axis length of 1. -
Method Summary
Modifier and TypeMethodDescriptionprotected intComputes a hash value for this transform.static MathTransformcreateGeodeticConversion(MathTransformFactory factory, double semiMajor, double semiMinor, Unit<Length> unit, boolean withHeight, EllipsoidToCentricTransform.TargetType target) Creates a transform from geographic to geocentric coordinates.static MathTransformcreateGeodeticConversion(MathTransformFactory factory, Ellipsoid ellipsoid, boolean withHeight) Creates a transform from geographic to Cartesian geocentric coordinates (convenience method).derivative(DirectPosition point) Computes the derivative at the given location.booleanequals(Object object, ComparisonMode mode) Compares the specified object with this math transform for equality.protected ContextualParametersReturns the parameters used for creating the complete conversion.Returns a description of the internal parameters of thisEllipsoidToCentricTransformtransform.Returns a copy of internal parameter values of thisEllipsoidToCentricTransformtransform.final intGets the dimension of input points, which is 2 or 3.final intGets the dimension of output points, which is 3.Returns whether the target coordinate system is Cartesian or Spherical.inverse()Returns the inverse of this transform.protected voidinverseTransform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, int numPts) Converts Cartesian coordinates (X,Y,Z) to ellipsoidal coordinates (λ,φ) or (λ,φ,h).transform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, boolean derivate) Converts the (λ,φ) or (λ,φ,h) geodetic coordinates to to (X,Y,Z) geocentric coordinates, and optionally returns the derivative at that location.voidtransform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, int numPts) Converts the (λ,φ) or (λ,φ,h) geodetic coordinates to to (X,Y,Z) geocentric coordinates.protected MathTransformtryConcatenate(boolean applyOtherFirst, MathTransform other, MathTransformFactory factory) If this transform expects three-dimensional inputs, and if the transform just before this one unconditionally sets the height to zero, then replaces this transform by a two-dimensional one.Methods inherited from class AbstractMathTransform
equals, formatTo, getDomain, hashCode, isIdentity, transform, transform, transform, transformMethods 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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eccentricitySquared
protected final double eccentricitySquaredThe square of eccentricity: 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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EllipsoidToCentricTransform
public EllipsoidToCentricTransform(double semiMajor, double semiMinor, Unit<Length> unit, boolean withHeight, EllipsoidToCentricTransform.TargetType target) Creates a transform from angles in radians on ellipsoid having a semi-major axis length of 1. More specificallyEllipsoidToCentricTransforminstances expect input coordinates as below:- longitudes in radians relative to the prime meridian (usually Greenwich),
- latitudes in radians,
- optionally heights above the ellipsoid, in units of an ellipsoid having a semi-major axis length of 1.
- distance from Earth center on the X axis (toward the intersection of prime meridian and equator),
- distance from Earth center on the Y axis (toward the intersection of 90°E meridian and equator),
- distance from Earth center on the Z axis (toward North pole).
Geographic to geocentric conversions
For converting geographic coordinates to geocentric coordinates,EllipsoidToCentricTransforminstances need to be concatenated with the following affine transforms:- Normalization before
EllipsoidToCentricTransform:- Conversion of (λ,φ) from degrees to radians
- Division of (h) by the semi-major axis length
- Denormalization after
EllipsoidToCentricTransform:- Multiplication of (X,Y,Z) by the semi-major axis length
EllipsoidToCentricTransformconstruction, the full conversion chain including the above affine transforms can be created bygetContextualParameters().completeTransform(factory, this)}.- Parameters:
semiMajor- the semi-major axis length.semiMinor- the semi-minor axis length.unit- the unit of measurement for the semi-axes and the ellipsoidal height.withHeight-trueif source geographic coordinates include an ellipsoidal height (i.e. are 3-D), orfalseif they are only 2-D.target- whether the target coordinate shall be Cartesian or Spherical.- See Also:
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Method Details
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createGeodeticConversion
public static MathTransform createGeodeticConversion(MathTransformFactory factory, double semiMajor, double semiMinor, Unit<Length> unit, boolean withHeight, EllipsoidToCentricTransform.TargetType target) throws FactoryException Creates a transform from geographic to geocentric coordinates. This factory method combines theEllipsoidToCentricTransforminstance with the steps needed for converting degrees to radians and expressing the results in units of the given ellipsoid.Input coordinates are expected to contain:
- longitudes in degrees relative to the prime meridian (usually Greenwich),
- latitudes in degrees,
- optionally heights above the ellipsoid, in units of the ellipsoid axis (usually metres).
- distance from Earth center on the X axis (toward the intersection of prime meridian and equator),
- distance from Earth center on the Y axis (toward the intersection of 90°E meridian and equator),
- distance from Earth center on the Z axis (toward North pole).
- Parameters:
factory- the factory to use for creating and concatenating the affine transforms.semiMajor- the semi-major axis length.semiMinor- the semi-minor axis length.unit- the unit of measurement for the semi-axes and the ellipsoidal height.withHeight-trueif source geographic coordinates include an ellipsoidal height (i.e. are 3-D), orfalseif they are only 2-D.target- whether the target coordinate shall be Cartesian or Spherical.- Returns:
- the conversion from geographic to geocentric coordinates.
- Throws:
FactoryException- if an error occurred while creating a transform.
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createGeodeticConversion
public static MathTransform createGeodeticConversion(MathTransformFactory factory, Ellipsoid ellipsoid, boolean withHeight) throws FactoryException Creates a transform from geographic to Cartesian geocentric coordinates (convenience method). This method is equivalent to the following:The target type is assumed Cartesian because this is the most frequently used target.return createGeodeticConversion(factory, ellipsoid.getSemiMajorAxis(), ellipsoid.getSemiMinorAxis(), ellipsoid.getAxisUnit(), withHeight, TargetType.CARTESIAN);- Parameters:
factory- the factory to use for creating and concatenating the affine transforms.ellipsoid- the semi-major and semi-minor axis lengths with their unit of measurement.withHeight-trueif source geographic coordinates include an ellipsoidal height (i.e. are 3-D), orfalseif they are only 2-D.- Returns:
- the conversion from geographic to Cartesian geocentric coordinates.
- Throws:
FactoryException- if an error occurred while creating a transform.
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getContextualParameters
Returns the parameters used for creating the complete conversion. Those parameters describe a sequence of normalize →this→ denormalize transforms, not including axis swapping. Those parameters are used for formatting Well Known Text (WKT) and error messages.- Overrides:
getContextualParametersin classAbstractMathTransform- Returns:
- the parameter values for the sequence of
normalize →
this→ denormalize transforms.
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getParameterValues
Returns a copy of internal parameter values of thisEllipsoidToCentricTransformtransform. The returned group contains parameter values for the number of dimensions and the eccentricity.Usage 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 classAbstractMathTransform- Returns:
- a copy of the internal parameter values for this transform.
- See Also:
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getParameterDescriptors
Returns a description of the internal parameters of thisEllipsoidToCentricTransformtransform. The returned group contains parameter descriptors for the number of dimensions and the eccentricity.- Specified by:
getParameterDescriptorsin interfaceParameterized- Overrides:
getParameterDescriptorsin classAbstractMathTransform- Returns:
- a description of the internal parameters.
- See Also:
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getSourceDimensions
public final int getSourceDimensions()Gets the dimension of input points, which is 2 or 3.- Specified by:
getSourceDimensionsin interfaceMathTransform- Specified by:
getSourceDimensionsin classAbstractMathTransform- Returns:
- 2 or 3.
- See Also:
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getTargetDimensions
public final int getTargetDimensions()Gets the dimension of output points, which is 3.- Specified by:
getTargetDimensionsin interfaceMathTransform- Specified by:
getTargetDimensionsin classAbstractMathTransform- Returns:
- always 3.
- See Also:
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getTargetType
Returns whether the target coordinate system is Cartesian or Spherical.- Returns:
- whether the target coordinate system is Cartesian or Spherical.
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derivative
Computes the derivative at the given location. This method relaxes a little bit theMathTransformcontract by accepting two- or three-dimensional points even if the number of dimensions does not match thegetSourceDimensions()value.Rational
That flexibility on the number of dimensions is required for calculation of inverse transform derivative, because that calculation needs to inverse a square matrix with all terms in it before to drop the last row in the two-dimensional case.- Specified by:
derivativein interfaceMathTransform- Overrides:
derivativein classAbstractMathTransform- Parameters:
point- the position where to evaluate the derivative.- Returns:
- the derivative at the specified point (never
null). - Throws:
TransformException- if the derivative cannot be evaluated at the specified point.
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transform
public Matrix transform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, boolean derivate) throws TransformException Converts the (λ,φ) or (λ,φ,h) geodetic coordinates to to (X,Y,Z) geocentric coordinates, 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 Converts the (λ,φ) or (λ,φ,h) geodetic coordinates to to (X,Y,Z) geocentric coordinates. This method performs the same conversion 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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inverseTransform
protected void inverseTransform(double[] srcPts, int srcOff, double[] dstPts, int dstOff, int numPts) throws TransformException Converts Cartesian coordinates (X,Y,Z) to ellipsoidal coordinates (λ,φ) or (λ,φ,h). This method is invoked by the transform returned byinverse().- 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 the calculation does not converge.
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inverse
Returns the inverse of this transform. The default implementation returns a transform that will delegate its work toinverseTransform(double[], int, double[], int, int).- Specified by:
inversein interfaceMathTransform- Overrides:
inversein classAbstractMathTransform- Returns:
- the conversion from (geo)centric to ellipsoidal coordinates.
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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 classAbstractMathTransform- 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 classAbstractMathTransform- 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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tryConcatenate
protected MathTransform tryConcatenate(boolean applyOtherFirst, MathTransform other, MathTransformFactory factory) throws FactoryException If this transform expects three-dimensional inputs, and if the transform just before this one unconditionally sets the height to zero, then replaces this transform by a two-dimensional one. The intent is to handle the following sequence of operations defined in the EPSG database:- Inverse of Geographic 3D to 2D conversion (EPSG:9659)
- Geographic/geocentric conversions (EPSG:9602)
EllipsoidToCentricTransforminstance allow the following optimizations:- Avoid computation of h value.
- Allow use of the more efficient
AffineTransformbefore this transform instead of a transform based on a matrix of size 4×3.
- Overrides:
tryConcatenatein classAbstractMathTransform- Parameters:
applyOtherFirst-trueif the transformation order isotherfollowed bythis, orfalseif the transformation order isthisfollowed byother.other- the other math transform to (pre-)concatenate with this transform.factory- the factory which is (indirectly) invoking this method, ornullif none.- Returns:
- the combined math transform, or
nullif no optimized combined transform is available. - Throws:
FactoryException- if an error occurred while combining the transforms.- See Also:
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