Package org.geotools.referencing.operation.projection

Class Mercator

Object

Formattable

AbstractMathTransform

MapProjection

Mercator

All Implemented Interfaces:

Serializable, MathTransform, MathTransform2D

Direct Known Subclasses:

Mercator1SP, Mercator2SP

public abstract class Mercator
extends MapProjection

Mercator Cylindrical Projection. The parallels and the meridians are straight lines and cross at right angles; this projection thus produces rectangular charts. The scale is true along the equator (by default) or along two parallels equidistant of the equator (if a scale factor other than 1 is used). This projection is used to represent areas close to the equator. It is also often used for maritime navigation because all the straight lines on the chart are loxodrome lines, i.e. a ship following this line would keep a constant azimuth on its compass.

This implementation handles both the 1 and 2 stardard parallel cases. For Mercator_1SP (EPSG code 9804), the line of contact is the equator. For Mercator_2SP (EPSG code 9805) lines of contact are symmetrical about the equator.

References:

• John P. Snyder (Map Projections - A Working Manual,
  U.S. Geological Survey Professional Paper 1395, 1987)
• "Coordinate Conversions and Transformations including Formulas",
  EPSG Guidence Note Number 7, Version 19.

Since:

2.1

Author:

André Gosselin, Martin Desruisseaux (PMO, IRD), Rueben Schulz, Simone Giannecchini

See Also:

• Mercator projection on MathWorld
• "mercator_1sp" on RemoteSensing.org
• "mercator_2sp" on RemoteSensing.org
• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class MapProjection

MapProjection.AbstractProvider

Field Summary

Fields

Modifier and Type	Field	Description
protected final double	standardParallel	Standard Parallel used for the Mercator2SP case.

Fields inherited from class MapProjection

centralMeridian, en0, en1, en2, en3, en4, excentricity, excentricitySquared, falseEasting, falseNorthing, globalScale, invertible, isSpherical, latitudeOfOrigin, LOGGER, scaleFactor, semiMajor, semiMinor, SKIP_SANITY_CHECKS

Fields inherited from class Formattable

SINGLE_LINE

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Mercator(ParameterValueGroup parameters)	Constructs a new map projection from the supplied parameters.

Method Summary

Modifier and Type	Method	Description
boolean	equals(Object object)	Compares the specified object with this map projection for equality.
ParameterValueGroup	getParameterValues()	Returns the parameter values for this map projection.
int	hashCode()	Returns a hash value for this projection.
protected Point2D	inverseTransformNormalized(double x, double y, Point2D ptDst)	Transforms the specified (x,y) coordinates and stores the result in ptDst.
protected Point2D	transformNormalized(double x, double y, Point2D ptDst)	Transforms the specified (λ,φ) coordinates (units in radians) and stores the result in ptDst (linear distance on a unit sphere).

Methods inherited from class MapProjection

checkReciprocal, getParameterDescriptors, getSourceDimensions, getTargetDimensions, getToleranceForAssertions, inv_mlfn, inverse, mlfn, orthodromicDistance, resetWarnings, transform, transform, transform

Methods inherited from class AbstractMathTransform

createTransformedShape, derivative, derivative, ensureNonNull, formatWKT, getName, isIdentity, needCopy, normalizeAngle, rollLongitude, 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

derivative, isIdentity, toWKT, transform, transform, transform

Methods inherited from interface MathTransform2D

createTransformedShape, derivative

Field Details

standardParallel

protected final double standardParallel

Standard Parallel used for the Mercator2SP case. Set to Double.NaN for the Mercator1SP case.

Constructor Details

Mercator

protected Mercator(ParameterValueGroup parameters)
            throws ParameterNotFoundException

Constructs a new map projection from the supplied parameters.

Parameters:

parameters - The parameter values in standard units.

Throws:

ParameterNotFoundException - if a mandatory parameter is missing.

Method Details

getParameterValues

public ParameterValueGroup getParameterValues()

Returns the parameter values for this map projection.

Overrides:

getParameterValues in class MapProjection

Returns:

A copy of the parameter values for this map projection.

See Also:

• Operation.getParameterValues()

transformNormalized

protected Point2D transformNormalized(double x,
 double y,
 Point2D ptDst)
                               throws ProjectionException

Transforms the specified (λ,φ) coordinates (units in radians) and stores the result in ptDst (linear distance on a unit sphere).

Specified by:

transformNormalized in class MapProjection

Parameters:

x - The longitude of the coordinate, in radians.

y - The latitude of the coordinate, in radians.

ptDst - the specified coordinate point that stores the result of transforming ptSrc, or null. Ordinates will be in a dimensionless unit, as a linear distance on a unit sphere or ellipse.

Returns:

the coordinate point after transforming (lambda, phi) and storing the result in ptDst.

Throws:

ProjectionException - if the point can't be transformed.

inverseTransformNormalized

protected Point2D inverseTransformNormalized(double x,
 double y,
 Point2D ptDst)
                                      throws ProjectionException

Transforms the specified (x,y) coordinates and stores the result in ptDst.

Specified by:

inverseTransformNormalized in class MapProjection

Parameters:

x - The easting of the coordinate, linear distance on a unit sphere or ellipse.

y - The northing of the coordinate, linear distance on a unit sphere or ellipse.

ptDst - the specified coordinate point that stores the result of transforming ptSrc, or null. Ordinates will be in radians.

Returns:

the coordinate point after transforming x, y and storing the result in ptDst.

Throws:

ProjectionException - if the point can't be transformed.

hashCode

public int hashCode()

Returns a hash value for this projection.

Overrides:

hashCode in class MapProjection

equals

public boolean equals(Object object)

Compares the specified object with this map projection for equality.

Overrides:

equals in class MapProjection

Parameters:

object - The object to compare with this transform.

Returns:

true if the given object is a transform of the same class and if, given identical source position, the transformed position would be the equals.