org.gicentre.utils.spatial

Class AlbersEqualAreaConic

java.lang.Object

org.gicentre.utils.spatial.AlbersEqualAreaConic

All Implemented Interfaces:

MapProjection

Direct Known Subclasses:

AlbersBC, AlbersUS, AlbersUSCont

public class AlbersEqualAreaConic
extends java.lang.Object
implements MapProjection

Class for representing Albers Equal Area Conic projections. Includes forward and inverse transforms from/to lat,long. Uses transformation equations from Snyder (1987) Atlas of Map Projections. Some code adapted from C program by T. Mittan, Feb, 1992 - see http://geography.usgs.gov/ftp/software/current_software/gctpc2/alberfor.c.

Version:

3.4, 5th February, 2016.

Author:

Jo Wood, giCentre, City University London and T. Mittan.

Field Summary

Fields

Modifier and Type	Field and Description
static int	FROM_LAT_LONG Indicates a transformation from latitude/longitude
static int	TO_LAT_LONG Indicates a transformation to latitude/longitude

Constructor Summary

Constructors

Constructor and Description
AlbersEqualAreaConic(Ellipsoid ellipsoid, double lat1, double lat2) Initialises the Albers converter with the given ellipsoid and standard parallels.
AlbersEqualAreaConic(Ellipsoid ellipsoid, double lat1, double lat2, double lon0, double lat0, double falseEast, double falseNorth) Initialises the Albers converter with the given ellipsoid.

Method Summary

Modifier and Type	Method and Description
processing.core.PVector	AlbersToLatLong(processing.core.PVector p) Converts the given coordinates that use the Albers equal area conic projection into a (longitude,latitude) location.
boolean	doInterpolation() Indicates whether the transformation should use nearest neighbour (false) or some interpolator (true).
java.lang.String	getDescription() Provides a general description of the transformation.
Ellipsoid	getEllipsoid() Reports the ellipsoid used in the transformation.
processing.core.PVector	invTransformCoords(processing.core.PVector p) Performs an inverse transformation (Albers to latitude/longitude) on the given location.
processing.core.PVector	latLongToAlbers(processing.core.PVector p) Converts the given (lng, lat) coordinates into a location referenced using the Albers equal area conic projection.
void	setInterpolation(boolean doInterpolation) Sets whether the transformation should use nearest neighbour (false) or some interpolator (true).
processing.core.PVector	transformCoords(processing.core.PVector p) Performs a forward transformation (latitude/longitude to Albers) on the given location.

Methods inherited from class java.lang.Object

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

Field Detail

FROM_LAT_LONG

public static final int FROM_LAT_LONG

Indicates a transformation from latitude/longitude

See Also:

Constant Field Values

TO_LAT_LONG

public static final int TO_LAT_LONG

Indicates a transformation to latitude/longitude

See Also:

Constant Field Values

Constructor Detail

AlbersEqualAreaConic

public AlbersEqualAreaConic(Ellipsoid ellipsoid,
                            double lat1,
                            double lat2)

Initialises the Albers converter with the given ellipsoid and standard parallels. Defaults to a projection centred at lng/lat of (0,0). The forward transformation will be from Lat/long to Albers equal area conic.

Parameters:

ellipsoid - to use in projection.

lat1 - First standard parallel in degrees (north of equator positive).

lat2 - Second standard parallel in degrees (north of equator positive).

AlbersEqualAreaConic

public AlbersEqualAreaConic(Ellipsoid ellipsoid,
                            double lat1,
                            double lat2,
                            double lon0,
                            double lat0,
                            double falseEast,
                            double falseNorth)

Initialises the Albers converter with the given ellipsoid. The forward transformation will be from Lat/long to Albers equal area conic.

Parameters:

ellipsoid - to use in projection.

lat1 - First standard parallel in degrees (north of equator positive).

lat2 - Second standard parallel in degrees (north of equator positive).

lon0 - Centre longitude in degrees (east of Greenwich positive).

lat0 - Centre latitude in degrees (north of equator positive).

falseEast - False easting (offset in metres).

falseNorth - False northing (offset in metres).

Method Detail

transformCoords

public processing.core.PVector transformCoords(processing.core.PVector p)

Performs a forward transformation (latitude/longitude to Albers) on the given location.

Specified by:

transformCoords in interface MapProjection

Parameters:

p - Location of point to transform.

Returns:

Transformed location coordinates.

invTransformCoords

public processing.core.PVector invTransformCoords(processing.core.PVector p)

Performs an inverse transformation (Albers to latitude/longitude) on the given location.

Specified by:

invTransformCoords in interface MapProjection

Parameters:

p - Location of point to transform.

Returns:

Transformed location coordinates.

getDescription

public java.lang.String getDescription()

Provides a general description of the transformation.

Specified by:

getDescription in interface MapProjection

Returns:

Description of the transformation.

doInterpolation

public boolean doInterpolation()

Indicates whether the transformation should use nearest neighbour (false) or some interpolator (true).

Returns:

True if transformation should perform some local interpolation.

setInterpolation

public void setInterpolation(boolean doInterpolation)

Sets whether the transformation should use nearest neighbour (false) or some interpolator (true).

Parameters:

doInterpolation - True if transformation should perform some local interpolation.

latLongToAlbers

public processing.core.PVector latLongToAlbers(processing.core.PVector p)

Converts the given (lng, lat) coordinates into a location referenced using the Albers equal area conic projection. Latitude/longitude coordinates should be in decimal degrees with positive North and positive East.

Parameters:

p - Longitude/latitude point. Longitude varies within +-180 degrees, latitude within +-90 degrees.

Returns:

Location (units in metres) using Albers coordinate system.

AlbersToLatLong

public processing.core.PVector AlbersToLatLong(processing.core.PVector p)

Converts the given coordinates that use the Albers equal area conic projection into a (longitude,latitude) location. Longitude and latitude will be in decimal degrees with positive North and positive East.

Parameters:

p - Location of point as an easting and northing in the Albers projection (metres from local origin).

Returns:

location in geographical coordinates (longitude/latitude decimal degrees).

getEllipsoid

public Ellipsoid getEllipsoid()

Reports the ellipsoid used in the transformation.

Returns:

Ellipsoid used in the UTM transformation.