com.bbn.openmap.proj
Class ProjMath

java.lang.Object
  |
  +--com.bbn.openmap.proj.ProjMath

public final class ProjMath

extends java.lang.Object

Math functions used by projection code.

Field Summary

static double	DATELINE_D Dateline longitude in radians.
static float	DATELINE_F Dateline longitude in radians.
static double	LON_RANGE_D Longitude range in radians.
static float	LON_RANGE_F Longitude range in radians.
static double	NORTH_POLE_D North pole latitude in radians.
static float	NORTH_POLE_F North pole latitude in radians.
static double	SOUTH_POLE_D South pole latitude in radians.
static float	SOUTH_POLE_F South pole latitude in radians.

Method Summary

static double[]	arrayDegToRad(double[] degs) Converts an array of decimal degrees double lat/lons to double radians in place.
static float[]	arrayDegToRad(float[] degs) Converts an array of decimal degrees float lat/lons to float radians in place.
static double[]	arrayRadToDeg(double[] rads) Converts an array of radian double lat/lons to decimal degrees in place.
static float[]	arrayRadToDeg(float[] rads) Converts an array of radian float lat/lons to decimal degrees in place.
static long	DEG_TO_SC(double deg) Convert between decimal degrees and scoords.
static double	degToRad(double deg) Convert degrees to radians.
static float	degToRad(float deg) Convert degrees to radians.
static float	geocentric_latitude(float lat, float flat) Calculate the geocentric latitude given a geographic latitude.
static float	geographic_latitude(float lat, float flat) Calculate the geographic latitude given a geocentric latitude.
protected static float	getScale(LatLonPoint ll1, LatLonPoint ll2, java.awt.Point point1, java.awt.Point point2, Projection projection) Given a couple of points representing a bounding box, find out what the scale should be in order to make those points appear at the corners of the projection.
static float	getScale(LatLonPoint ll1, LatLonPoint ll2, Projection projection) Given a couple of points representing a bounding box, find out what the scale should be in order to make those points appear at the corners of the projection.
static float	getScale(java.awt.Point point1, java.awt.Point point2, Projection projection) Given a couple of points representing a bounding box, find out what the scale should be in order to make those points appear at the corners of the projection.
static int	hashLatLon(float lat, float lon) Generate a hashCode value for a lat/lon pair.
static float	lonDistance(float lon1, float lon2) Calculate the shortest arc distance between two lons.
static double	normalize_latitude(double lat, double epsilon) Normalizes radian latitude.
static float	normalize_latitude(float lat, float epsilon) Normalizes radian latitude.
static double	qint(double x) Rounds the quantity away from 0.
static double	radToDeg(double rad) Convert radians to degrees.
static float	radToDeg(float rad) Convert radians to degrees.
static double	roundAdjust(double x) rounds the quantity away from 0.
static double	SC_TO_DEG(int sc) Convert between decimal degrees and scoords.
static float	sphericalUnitsToDeg(float u, float uCircumference) Converts units (km, nm, miles, etc) to decimal degrees for a spherical planet.
static float	sphericalUnitsToRad(float u, float uCircumference) Converts units (km, nm, miles, etc) to arc radians for a spherical planet.
static double	wrap_longitude(double lon) Sets radian longitude to something sane.
static float	wrap_longitude(float lon) Sets radian longitude to something sane.

Methods inherited from class java.lang.Object

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

Field Detail

NORTH_POLE_F

public static final transient float NORTH_POLE_F

North pole latitude in radians.

See Also:

Constant Field Values

SOUTH_POLE_F

public static final transient float SOUTH_POLE_F

South pole latitude in radians.

See Also:

Constant Field Values

NORTH_POLE_D

public static final transient double NORTH_POLE_D

North pole latitude in radians.

See Also:

Constant Field Values

SOUTH_POLE_D

public static final transient double SOUTH_POLE_D

South pole latitude in radians.

See Also:

Constant Field Values

DATELINE_F

public static final transient float DATELINE_F

Dateline longitude in radians.

See Also:

Constant Field Values

DATELINE_D

public static final transient double DATELINE_D

Dateline longitude in radians.

See Also:

Constant Field Values

LON_RANGE_F

public static final transient float LON_RANGE_F

Longitude range in radians.

See Also:

Constant Field Values

LON_RANGE_D

public static final transient double LON_RANGE_D

Longitude range in radians.

See Also:

Constant Field Values

Method Detail

roundAdjust

public static final double roundAdjust(double x)

rounds the quantity away from 0.

Parameters:

x - in value

Returns:

double

See Also:

qint(double)

qint

public static final double qint(double x)

Rounds the quantity away from 0.

Parameters:

x - value

Returns:

double

lonDistance

public static final float lonDistance(float lon1,
                                      float lon2)

Calculate the shortest arc distance between two lons.

Parameters:

lon1 - radians

lon2 - radians

Returns:

float distance

DEG_TO_SC

public static final long DEG_TO_SC(double deg)

Convert between decimal degrees and scoords.

Parameters:

deg - degrees

Returns:

long scoords

SC_TO_DEG

public static final double SC_TO_DEG(int sc)

Convert between decimal degrees and scoords.

Parameters:

sc - scoords

Returns:

double decimal degrees

radToDeg

public static final double radToDeg(double rad)

Convert radians to degrees.

Parameters:

rad - radians

Returns:

double decimal degrees

radToDeg

public static final float radToDeg(float rad)

Convert radians to degrees.

Parameters:

rad - radians

Returns:

float decimal degrees

degToRad

public static final double degToRad(double deg)

Convert degrees to radians.

Parameters:

deg - degrees

Returns:

double radians

degToRad

public static final float degToRad(float deg)

Convert degrees to radians.

Parameters:

deg - degrees

Returns:

float radians

hashLatLon

public static final int hashLatLon(float lat,
                                   float lon)

Generate a hashCode value for a lat/lon pair.

Parameters:

lat - latitude

lon - longitude

Returns:

int hashcode

arrayDegToRad

public static final float[] arrayDegToRad(float[] degs)

Converts an array of decimal degrees float lat/lons to float radians in place.

Parameters:

degs - float[] lat/lons in decimal degrees

Returns:

float[] lat/lons in radians

arrayRadToDeg

public static final float[] arrayRadToDeg(float[] rads)

Converts an array of radian float lat/lons to decimal degrees in place.

Parameters:

rads - float[] lat/lons in radians

Returns:

float[] lat/lons in decimal degrees

arrayDegToRad

public static final double[] arrayDegToRad(double[] degs)

Converts an array of decimal degrees double lat/lons to double radians in place.

Parameters:

degs - double[] lat/lons in decimal degrees

Returns:

double[] lat/lons in radians

arrayRadToDeg

public static final double[] arrayRadToDeg(double[] rads)

Converts an array of radian double lat/lons to decimal degrees in place.

Parameters:

rads - double[] lat/lons in radians

Returns:

double[] lat/lons in decimal degrees

normalize_latitude

public static final float normalize_latitude(float lat,
                                             float epsilon)

Normalizes radian latitude. Normalizes latitude if at or exceeds epsilon distance from a pole.

Parameters:

lat - float latitude in radians

epsilon - epsilon (>= 0) radians distance from pole

Returns:

float latitude (-PI/2 <= phi <= PI/2)

See Also:

Proj.normalize_latitude(float), LatLonPoint.normalize_latitude(float)

normalize_latitude

public static final double normalize_latitude(double lat,
                                              double epsilon)

Normalizes radian latitude. Normalizes latitude if at or exceeds epsilon distance from a pole.

Parameters:

lat - double latitude in radians

epsilon - epsilon (>= 0) radians distance from pole

Returns:

double latitude (-PI/2 <= phi <= PI/2)

See Also:

Proj.normalize_latitude(float), LatLonPoint.normalize_latitude(float)

wrap_longitude

public static final float wrap_longitude(float lon)

Sets radian longitude to something sane.

Parameters:

lon - float longitude in radians

Returns:

float longitude (-PI <= lambda < PI)

See Also:

LatLonPoint.wrap_longitude(float)

wrap_longitude

public static final double wrap_longitude(double lon)

Sets radian longitude to something sane.

Parameters:

lon - double longitude in radians

Returns:

double longitude (-PI <= lambda < PI)

See Also:

wrap_longitude(float)

sphericalUnitsToDeg

public static final float sphericalUnitsToDeg(float u,
                                              float uCircumference)

Converts units (km, nm, miles, etc) to decimal degrees for a spherical planet. This does not check for arc distances > 1/2 planet circumference, which are better represented as (2pi - calculated arc).

Parameters:

u - units float value

uCircumference - units circumference of planet

Returns:

float decimal degrees

sphericalUnitsToRad

public static final float sphericalUnitsToRad(float u,
                                              float uCircumference)

Converts units (km, nm, miles, etc) to arc radians for a spherical planet. This does not check for arc distances > 1/2 planet circumference, which are better represented as (2pi - calculated arc).

Parameters:

u - units float value

uCircumference - units circumference of planet

Returns:

float arc radians

geocentric_latitude

public static final float geocentric_latitude(float lat,
                                              float flat)

Calculate the geocentric latitude given a geographic latitude. According to John Synder:
"The geographic or geodetic latitude is the angle which a line perpendicular to the surface of the ellipsoid at the given point makes with the plane of the equator. ...The geocentric latitude is the angle made by a line to the center of the ellipsoid with the equatorial plane". ( Map Projections --A Working Manual , p 13)

Translated from Ken Anderson's lisp code Freeing the Essence of Computation

Parameters:

lat - float geographic latitude in radians

flat - float flatening factor

Returns:

float geocentric latitude in radians

See Also:

geographic_latitude(float, float)

geographic_latitude

public static final float geographic_latitude(float lat,
                                              float flat)

Calculate the geographic latitude given a geocentric latitude. Translated from Ken Anderson's lisp code Freeing the Essence of Computation

Parameters:

lat - float geocentric latitude in radians

flat - float flatening factor

Returns:

float geographic latitude in radians

See Also:

geocentric_latitude(float, float)

getScale

public static float getScale(LatLonPoint ll1,
                             LatLonPoint ll2,
                             Projection projection)

Given a couple of points representing a bounding box, find out what the scale should be in order to make those points appear at the corners of the projection.

Parameters:

ll1 - the upper left coordinates of the bounding box.

ll2 - the lower right coordinates of the bounding box.

projection - the projection to use for other projection parameters, like map width and map height.

getScale

public static float getScale(java.awt.Point point1,
                             java.awt.Point point2,
                             Projection projection)

Given a couple of points representing a bounding box, find out what the scale should be in order to make those points appear at the corners of the projection.

Parameters:

point1 - a java.awt.Point reflecting a pixel spot on the projection, usually the upper left corner of the area of interest.

point2 - a java.awt.Point reflecting a pixel spot on the projection, usually the lower right corner of the area of interest.

projection - the projection to use for other projection parameters, like map width and map height.

getScale

protected static float getScale(LatLonPoint ll1,
                                LatLonPoint ll2,
                                java.awt.Point point1,
                                java.awt.Point point2,
                                Projection projection)

Given a couple of points representing a bounding box, find out what the scale should be in order to make those points appear at the corners of the projection.

Parameters:

ll1 - the upper left coordinates of the bounding box.

ll2 - the lower right coordinates of the bounding box.

point1 - a java.awt.Point reflecting a pixel spot on the projection that matches the ll1 coordinate, the upper left corner of the area of interest.

point2 - a java.awt.Point reflecting a pixel spot on the projection that matches the ll2 coordinate, usually the lower right corner of the area of interest.

projection - the projection to use to query to get the scale for, for projection type and height and width.