jfxtras.labs.map

Class Mercator

java.lang.Object

jfxtras.labs.map.Mercator

public class Mercator
extends java.lang.Object

This class implements the Mercator Projection as it is used by Openstreetmap (and google). It provides methods to translate coordinates from 'map space' into latitude and longitude (on the WGS84 ellipsoid) and vice versa. Map space is measured in pixels. The origin of the map space is the top left corner. The map space origin (0,0) has latitude ~85 and longitude -180

Field Summary

Fields

Modifier and Type	Field and Description
static double	MAX_LAT
static double	MIN_LAT

Constructor Summary

Constructors

Constructor and Description
Mercator()

Method Summary

Methods

Modifier and Type	Method and Description
static int	falseEasting(int aZoomlevel)
static int	falseNorthing(int aZoomlevel)
static int	getMaxPixels(int aZoomlevel) Returns the absolute number of pixels in y or x, defined as: 2^Zoomlevel * TILE_WIDTH where TILE_WIDTH is the width of a tile in pixels
static int	latToY(double aLat, int aZoomlevel) Transforms latitude to pixel space
static int	lonToX(double aLongitude, int aZoomlevel) Transform longitude to pixel space
static double	radius(int aZoomlevel)
static double	xToLon(int aX, int aZoomlevel) Transforms pixel coordinate X to longitude
static double	yToLat(int aY, int aZoomlevel) Transforms pixel coordinate Y to latitude

Methods inherited from class java.lang.Object

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

Field Detail

MAX_LAT

public static final double MAX_LAT

See Also:

Constant Field Values

MIN_LAT

public static final double MIN_LAT

See Also:

Constant Field Values

Constructor Detail

Mercator

public Mercator()

Method Detail

radius

public static double radius(int aZoomlevel)

getMaxPixels

public static int getMaxPixels(int aZoomlevel)

Returns the absolute number of pixels in y or x, defined as: 2^Zoomlevel * TILE_WIDTH where TILE_WIDTH is the width of a tile in pixels

Parameters:

aZoomlevel -

Returns:

falseEasting

public static int falseEasting(int aZoomlevel)

falseNorthing

public static int falseNorthing(int aZoomlevel)

lonToX

public static int lonToX(double aLongitude,
         int aZoomlevel)

Transform longitude to pixel space

Mathematical optimization
x = radius(aZoomlevel) * toRadians(aLongitude) + falseEasting(aZoomLevel)
x = getMaxPixels(aZoomlevel) / (2 * PI) * (aLongitude * PI) / 180 + getMaxPixels(aZoomlevel) / 2
x = getMaxPixels(aZoomlevel) * aLongitude / 360 + 180 * getMaxPixels(aZoomlevel) / 360
x = getMaxPixels(aZoomlevel) * (aLongitude + 180) / 360


Parameters:

aLongitude - [-180..180]

Returns:

[0..2^Zoomlevel*TILE_SIZE[

latToY

public static int latToY(double aLat,
         int aZoomlevel)

Transforms latitude to pixel space

Mathematical optimization
log(u) := log((1.0 + sin(toRadians(aLat))) / (1.0 - sin(toRadians(aLat))
y = -1 * (radius(aZoomlevel) / 2 * log(u)))) - falseNorthing(aZoomlevel))
y = -1 * (getMaxPixel(aZoomlevel) / 2 * PI / 2 * log(u)) - -1 * getMaxPixel(aZoomLevel) / 2
y = getMaxPixel(aZoomlevel) / (-4 * PI) * log(u)) + getMaxPixel(aZoomLevel) / 2
y = getMaxPixel(aZoomlevel) * ((log(u) / (-4 * PI)) + 1/2)


Parameters:

aLat - [-90...90]

Returns:

[0..2^Zoomlevel*TILE_SIZE[

xToLon

public static double xToLon(int aX,
            int aZoomlevel)

Transforms pixel coordinate X to longitude

Mathematical optimization
lon = toDegree((aX - falseEasting(aZoomlevel)) / radius(aZoomlevel))
lon = 180 / PI * ((aX - getMaxPixels(aZoomlevel) / 2) / getMaxPixels(aZoomlevel) / (2 * PI)
lon = 180 * ((aX - getMaxPixels(aZoomlevel) / 2) / getMaxPixels(aZoomlevel))
lon = 360 / getMaxPixels(aZoomlevel) * (aX - getMaxPixels(aZoomlevel) / 2)
lon = 360 * aX / getMaxPixels(aZoomlevel) - 180


Parameters:

aX - [0..2^Zoomlevel*TILE_WIDTH[

Returns:

]-180..180[

yToLat

public static double yToLat(int aY,
            int aZoomlevel)

Transforms pixel coordinate Y to latitude

Parameters:

aY - [0..2^Zoomlevel*TILE_WIDTH[

Returns:

[MIN_LAT..MAX_LAT] is about [-85..85]