org.openstreetmap.josm.data.projection.proj

Class Mercator

java.lang.Object

org.openstreetmap.josm.data.projection.proj.AbstractProj

org.openstreetmap.josm.data.projection.proj.Mercator

All Implemented Interfaces:

IScaleFactorProvider, Proj

public class Mercator
extends AbstractProj
implements IScaleFactorProvider

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 1 SP (EPSG code 9804), the line of contact is the equator. For 2 SP (EPSG code 9805) lines of contact are symmetrical about the equator.

This class has been derived from the implementation of the Geotools project; git 8cbf52d, org.geotools.referencing.operation.projection.Mercator at the time of migration.

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.

See Also:

Mercator projection on MathWorld, "mercator_1sp" on RemoteSensing.org, "mercator_2sp" on RemoteSensing.org

Field Summary

Fields

Modifier and Type	Field and Description
private static double	EPSILON Maximum difference allowed when comparing real numbers.
protected double	scaleFactor

Fields inherited from class org.openstreetmap.josm.data.projection.proj.AbstractProj

e, e2, en0, en1, en2, en3, en4, spherical

Constructor Summary

Constructors

Constructor and Description
Mercator()

Method Summary

Modifier and Type	Method and Description
Bounds	getAlgorithmBounds() Return the bounds where this projection is applicable.
java.lang.String	getName() Replies a human readable name of this projection.
java.lang.String	getProj4Id() Replies the Proj.4 identifier.
double	getScaleFactor() Get the scale factor.
void	initialize(ProjParameters params) Initialize the projection using the provided parameters.
double[]	invproject(double x, double y) Convert east/north to lat/lon.
boolean	lonIsLinearToEast() Checks whether the result of projecting a lon coordinate only has a linear relation to the east coordinate and is not related to lat/north at all.
double[]	project(double y, double x) Convert lat/lon to east/north.

Methods inherited from class org.openstreetmap.josm.data.projection.proj.AbstractProj

aasin, cphi2, invMlfn, isGeographic, mlfn, msfn, tsfn

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

EPSILON

private static final double EPSILON

Maximum difference allowed when comparing real numbers.

See Also:

Constant Field Values

scaleFactor

protected double scaleFactor

Constructor Detail

Mercator

public Mercator()

Method Detail

getName

public java.lang.String getName()

Description copied from interface: Proj

Replies a human readable name of this projection.

Specified by:

getName in interface Proj

Returns:

The projection name. must not be null.

getProj4Id

public java.lang.String getProj4Id()

Description copied from interface: Proj

Replies the Proj.4 identifier.

Specified by:

getProj4Id in interface Proj

Returns:

The Proj.4 identifier (as reported by cs2cs -lp). If no id exists, return null.

initialize

public void initialize(ProjParameters params)
                throws ProjectionConfigurationException

Description copied from interface: Proj

Initialize the projection using the provided parameters.

Specified by:

initialize in interface Proj

Overrides:

initialize in class AbstractProj

Parameters:

params - The projection parameters

Throws:

ProjectionConfigurationException - in case parameters are not suitable

project

public double[] project(double y,
                        double x)

Description copied from interface: Proj

Convert lat/lon to east/north.

Specified by:

project in interface Proj

Parameters:

y - the latitude in radians

x - the longitude in radians

Returns:

array of length 2, containing east and north value in meters, divided by the semi major axis of the ellipsoid.

invproject

public double[] invproject(double x,
                           double y)

Description copied from interface: Proj

Convert east/north to lat/lon.

Specified by:

invproject in interface Proj

Parameters:

x - east value in meters, divided by the semi major axis of the ellipsoid

y - north value in meters, divided by the semi major axis of the ellipsoid

Returns:

array of length 2, containing lat and lon in radians.

getAlgorithmBounds

public Bounds getAlgorithmBounds()

Description copied from interface: Proj

Return the bounds where this projection is applicable. This is a fallback for when the projection bounds are not specified explicitly. In this area, the round trip lat/lon -> east/north -> lat/lon should return the starting value with small error. In addition, regions with extreme distortions should be excluded, if possible. It need not be the absolute maximum, but rather an area that is safe to display in JOSM and contain everything that one would expect to use.

Specified by:

getAlgorithmBounds in interface Proj

Returns:

the bounds where this projection is applicable, null if unknown

getScaleFactor

public double getScaleFactor()

Description copied from interface: IScaleFactorProvider

Get the scale factor. Will be multiplied by the scale factor parameter, if supplied by the user explicitly.

Specified by:

getScaleFactor in interface IScaleFactorProvider

Returns:

the scale factor

lonIsLinearToEast

public boolean lonIsLinearToEast()

Description copied from interface: Proj

Checks whether the result of projecting a lon coordinate only has a linear relation to the east coordinate and is not related to lat/north at all.

Specified by:

lonIsLinearToEast in interface Proj

Returns:

true if lon has a linear relationship to east only.