Class InterpolatedGeocentricTransform
Object
FormattableObject
AbstractMathTransform
DatumShiftTransform
InterpolatedGeocentricTransform
- All Implemented Interfaces:
- Serializable,- Parameterized,- LenientComparable,- MathTransform
Transforms between two geographic CRS by performing geocentric translations interpolated from a grid file.
 This transform is used mainly for "France geocentric interpolation" (ESPG:9655) datum shifts,
 but Apache SIS implementation allows the use for other regions.
 
Algorithm
This class transforms two- or three- dimensional coordinates from a geographic CRS to another geographic CRS. The changes between source and target coordinates are small (usually less than 400 metres), but vary for every position. Those changes are provided in a datum shift grid, usually loaded from one or two files.Many datum shift grids like NADCON and NTv2 apply the changes directly on geographic coordinates.
 This relatively simple case is handled by InterpolatedTransform.
 But the InterpolatedGeocentricTransform algorithm uses the grid in a more complex way:
- Convert input geographic coordinate (λ,φ) to geocentric coordinate (X,Y,Z).
- Ask DatumShiftGridfor the offset to apply for coordinate (λ,φ). But instead of returning a (Δλ, Δφ) offset, the grid shall return a (ΔX, ΔY, ΔZ) offset.
- Convert the shifted geocentric coordinate (X+ΔX, Y+ΔY, Z+ΔZ) back to a geographic coordinate.
Source: IGN document 
 NTG_88.pdf,
 "Grille de paramètres de transformation de coordonnées"
 at http://www.ign.fr.
 Note however that the signs of (ΔX, ΔY, ΔZ) values expected by this class are the opposite of the
 signs used in NTG_88 document. This is because NTG_88 grid defines shifts from target to source,
 while this class expects shifts from source to target.
 Note: this algorithm is not the same as a (theoretical) EllipsoidToCentricTransform →
 InterpolatedTransform → (inverse of EllipsoidToCentricTransform) concatenation
 because the DatumShiftGrid inputs are geographic coordinates even if the interpolated
 grid values are in geocentric space.
Performance consideration
InterpolatedMolodenskyTransform performs the same calculation more efficiently at the cost of
 a few centimetres error. Both classes are instantiated in the same way and expect the same inputs.- Since:
- 0.7
- See Also:
Defined in the sis-referencing module
- 
Constructor SummaryConstructorsModifierConstructorDescriptionprotectedInterpolatedGeocentricTransform(Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, DatumShiftGrid<Angle, Length> grid) Creates a transform from the specified parameters.
- 
Method SummaryModifier and TypeMethodDescriptionstatic MathTransformcreateGeodeticTransformation(MathTransformFactory factory, Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, DatumShiftGrid<Angle, Length> grid) Creates a transformation between two geographic CRS.intGets the dimension of input points.intGets the dimension of output points.inverse()Returns the inverse of this interpolated geocentric transform.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.Methods inherited from class DatumShiftTransformcomputeHashCode, equals, getContextualParameters, getParameterValuesMethods inherited from class AbstractMathTransformderivative, equals, formatTo, getDomain, getParameterDescriptors, hashCode, isIdentity, transform, transform, transform, transform, transform, tryConcatenateMethods inherited from class FormattableObjectprint, toString, toString, toWKTMethods inherited from class Objectclone, finalize, getClass, notify, notifyAll, wait, wait, waitMethods inherited from interface MathTransformtoWKT
- 
Constructor Details- 
InterpolatedGeocentricTransformprotected InterpolatedGeocentricTransform(Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, DatumShiftGrid<Angle, Length> grid) Creates a transform from the specified parameters. ThisInterpolatedGeocentricTransformclass 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.
 InterpolatedGeocentricTransforminstances need to be concatenated with the following affine transforms:- Normalization before InterpolatedGeocentricTransform:- Conversion of (λ,φ) from degrees to radians.
 
- Denormalization after InterpolatedGeocentricTransform:- Conversion of (λ,φ) from radians to degrees.
 
 InterpolatedGeocentricTransformconstruction, 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.
- grid- the grid of datum shifts from source to target datum. The- DatumShiftGrid.interpolateInCell(…)method shall compute (ΔX, ΔY, ΔZ) translations from source to target in the unit of source ellipsoid axes.
- See Also:
 
 
- 
- 
Method Details- 
createGeodeticTransformationpublic static MathTransform createGeodeticTransformation(MathTransformFactory factory, Ellipsoid source, boolean isSource3D, Ellipsoid target, boolean isTarget3D, DatumShiftGrid<Angle, Length> grid) throws FactoryExceptionCreates a transformation between two geographic CRS. This factory method combines theInterpolatedGeocentricTransforminstance 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.
 gridinstance shall expect geographic coordinates (λ,φ) in radians.- 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.
- grid- the grid of datum shifts from source to target datum. The- DatumShiftGrid.interpolateInCell(…)method shall compute (ΔX, ΔY, ΔZ) translations from source to target in the unit of source ellipsoid axes.
- Returns:
- the transformation between geographic coordinates in degrees.
- Throws:
- FactoryException- if an error occurred while creating a transform.
 
- 
getSourceDimensionspublic int getSourceDimensions()Gets the dimension of input points.- Specified by:
- getSourceDimensionsin interface- MathTransform
- Specified by:
- getSourceDimensionsin class- AbstractMathTransform
- Returns:
- the input dimension, which is 2 or 3.
- See Also:
 
- 
getTargetDimensionspublic int getTargetDimensions()Gets the dimension of output points.- Specified by:
- getTargetDimensionsin interface- MathTransform
- Specified by:
- getTargetDimensionsin class- AbstractMathTransform
- Returns:
- the output dimension, which is 2 or 3.
- See Also:
 
- 
transformpublic 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 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- nullif 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, or- falseif 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:
 
- 
inverseReturns the inverse of this interpolated geocentric transform. The source ellipsoid of the returned transform will be the target ellipsoid of this transform, and conversely.- Specified by:
- inversein interface- MathTransform
- Overrides:
- inversein class- AbstractMathTransform
- Returns:
- a transform from the target ellipsoid to the source ellipsoid of this transform.
 
 
-