org.geotools.referencing.operation.transform

Class EarthGravitationalModel

Object

Formattable

AbstractMathTransform

VerticalTransform

EarthGravitationalModel

All Implemented Interfaces:

MathTransform

public final class EarthGravitationalModel
extends VerticalTransform

Transforms vertical coordinates using coefficients from the Earth Gravitational Model.

Aknowledgement
This class is an adaption of Fortran code clenqt.for from the National Geospatial-Intelligence Agency and available in public domain. The normalized geopotential coefficients file bundled in this module is an adaptation of egm180.nor file, with some spaces trimmed.

Since:

2.3

Author:

Pierre Cardinal, Martin Desruisseaux

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	EarthGravitationalModel.Provider The provider for EarthGravitationalModel.

Nested classes/interfaces inherited from class AbstractMathTransform

AbstractMathTransform.Inverse

Field Summary

Fields inherited from class Formattable

SINGLE_LINE

Method Summary

Modifier and Type	Method and Description
ParameterDescriptorGroup	getParameterDescriptors() Returns the parameter descriptors for this math transform.
ParameterValueGroup	getParameterValues() Returns the parameters for this math transform.
double	heightOffset(double longitude, double latitude, double height) Returns the value to add to a height above the ellipsoid in order to get a height above the geoid for the specified geographic coordinate.
protected void	load(String filename) Loads the coefficients from the specified ASCII file and initialize the internal clenshaw arrays.

Methods inherited from class VerticalTransform

getSourceDimensions, getTargetDimensions, transform, transform

Methods inherited from class AbstractMathTransform

createTransformedShape, derivative, derivative, ensureNonNull, equals, formatWKT, getName, hashCode, inverse, isIdentity, needCopy, normalizeAngle, rollLongitude, transform, transform, transform, transform

Methods inherited from class Formattable

cleanupThreadLocals, toString, toWKT, toWKT, toWKT, toWKT

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface MathTransform

toWKT

Method Detail

load

protected void load(String filename)
             throws IOException

Loads the coefficients from the specified ASCII file and initialize the internal clenshaw arrays.

Note: ASCII may looks like an unefficient format for binary distribution. A binary file with coefficient values read by DataInput.readDouble() would be more compact than an uncompressed ASCII file. However, binary files are hard to compress by the ZIP algorithm. Our experience show that a 675 kb uncompressed ASCII file is only 222 kb after ZIP or JAR compression. The same data as a binary file is 257 kb uncompressed and 248 kb compressed. So surprisingly, the ASCII file is more compact than the binary file after compression. Since it is the primary format provided by the Earth-Info web site, we use it directly in order to avoid a multiplication of formats.

Parameters:

filename - The filename (e.g. "WGS84.cof", relative to this class directory.

Throws:

IOException - if the file can't be read or has an invalid content.

heightOffset

public double heightOffset(double longitude,
                           double latitude,
                           double height)
                    throws TransformException

Returns the value to add to a height above the ellipsoid in order to get a height above the geoid for the specified geographic coordinate.

Specified by:

heightOffset in class VerticalTransform

Parameters:

longitude - The geodetic longitude, in decimal degrees.

latitude - The geodetic latitude, in decimal degrees.

height - The height above the ellipsoid in metres.

Returns:

The value to add in order to get the height above the geoid (in metres).

Throws:

TransformException - if the offset can't be computed for the specified coordinates.

getParameterDescriptors

public ParameterDescriptorGroup getParameterDescriptors()

Returns the parameter descriptors for this math transform.

Overrides:

getParameterDescriptors in class AbstractMathTransform

Returns:

The parameter descriptors for this math transform, or null.

See Also:

OperationMethod.getParameters()

getParameterValues

public ParameterValueGroup getParameterValues()

Returns the parameters for this math transform.

Overrides:

getParameterValues in class AbstractMathTransform

Returns:

A copy of the parameter values for this math transform, or null.

See Also:

Operation.getParameterValues()