au.gov.amsa.util.navigation

Class Position

java.lang.Object

au.gov.amsa.util.navigation.Position

public class Position
extends Object

Can use commons-math3 FastMath for most trig functions exception for atan,atan2 (see here).

Author:

dxm

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Position.LongitudePair

Constructor Summary

Constructors

Constructor and Description
Position(double lat, double lon)
Position(double lat, double lon, double alt)

Method Summary

Modifier and Type	Method and Description
static void	assertWithMsg(boolean assertion, String msg)
static Position	create(double lat, double lon)
static Position	create(double lat, double lon, double alt)
Position	ensureContinuous(Position lastPosition) normalize the lat lon values of this to ensure that no large longitude jumps are made from lastPosition (e.g.
boolean	equals(Object o)
double	getAlt()
double	getBearingDegrees(Position position) Returns a great circle bearing in degrees in the range 0 to 360.
static double	getBearingDifferenceDegrees(double bearing1, double bearing2) returns difference in degrees in the range -180 to 180
Position	getClosestIntersectionWithSegment(Position p1, Position p2)
double	getDistanceKmToPath(Position p1, Position p2) calculates the distance of a point to the great circle path between p1 and p2.
double	getDistanceToKm(Position position) returns distance between two WGS84 positions according to Vincenty's formula from Wikipedia
double	getDistanceToPathKm(List<Position> positions)
double	getDistanceToSegmentKm(Position p1, Position p2)
Position[]	getEarthLimb(int radials) Return an array of Positions representing the earths limb (aka: horizon) as viewed from this Position in space.
double	getLat()
Double	getLatitudeOnGreatCircle(Position position, double longitudeDegrees) From http://williams.best.vwh.net/avform.htm (Latitude of point on GC).
double	getLon()
Position.LongitudePair	getLongitudeOnGreatCircle(Position position, double latitudeDegrees) Returns null if no crossing of latitude otherwise return two longitude candidates.
Position	getPositionAlongPath(Position position, double proportion) Returns a position along a path according to the proportion value
List<Position>	getPositionsAlongPath(Position position, double maxSegmentLengthKm)
int	hashCode()
boolean	isOutside(List<Position> path, double minDistanceKm)
boolean	isWithin(List<Position> positions)
static double	longitudeDiff(double a, double b) Returns the difference between two longitude values.
Position	normalizeLongitude()
Position	predict(double distanceKm, double courseDegrees) Predicts position travelling along a great circle arc based on the Haversine formula.
static double	to180(double d) Converts an angle in degrees to range -180< x <= 180.
Position	to360()
static double	toDegrees(double degrees, double minutes, double seconds)
static String	toDegreesMinutesDecimalMinutesLatitude(double lat)
static String	toDegreesMinutesDecimalMinutesLongitude(double lon)
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Position

public Position(double lat,
                double lon)

Parameters:

lat - in degrees

lon - in degrees

Position

public Position(double lat,
                double lon,
                double alt)

Parameters:

lat - in degrees

lon - in degrees

alt - in metres

Method Detail

create

public static Position create(double lat,
                              double lon)

create

public static Position create(double lat,
                              double lon,
                              double alt)

getLat

public final double getLat()

getLon

public final double getLon()

getAlt

public final double getAlt()

toString

public final String toString()

Overrides:

toString in class Object

predict

public final Position predict(double distanceKm,
                              double courseDegrees)

Predicts position travelling along a great circle arc based on the Haversine formula. From http://www.movable-type.co.uk/scripts/latlong.html

Parameters:

distanceKm -

courseDegrees -

Returns:

toDegrees

public static double toDegrees(double degrees,
                               double minutes,
                               double seconds)

getLatitudeOnGreatCircle

public Double getLatitudeOnGreatCircle(Position position,
                                       double longitudeDegrees)

From http://williams.best.vwh.net/avform.htm (Latitude of point on GC).

Parameters:

position -

longitudeDegrees -

Returns:

getLongitudeOnGreatCircle

public Position.LongitudePair getLongitudeOnGreatCircle(Position position,
                                                        double latitudeDegrees)

Returns null if no crossing of latitude otherwise return two longitude candidates. From http://williams.best.vwh.net/avform.htm (Crossing parallels).

Parameters:

position -

latitudeDegrees -

Returns:

getEarthLimb

public final Position[] getEarthLimb(int radials)

Return an array of Positions representing the earths limb (aka: horizon) as viewed from this Position in space. This position must have altitude > 0 The array returned will have the specified number of elements (radials). This method is useful for the calculation of satellite footprints or the position of the Earth's day/night terminator. This formula from Aviation Formula by Ed Williams (http://williams.best.vwh.net/avform.htm)

Parameters:

radials - the number of radials to calculated (evenly spaced around the circumference of the circle

Returns:

An array of radial points a fixed distance from this point representing the Earth's limb as viewed from this point in space.

getDistanceToKm

public final double getDistanceToKm(Position position)

returns distance between two WGS84 positions according to Vincenty's formula from Wikipedia

Parameters:

position -

Returns:

getBearingDegrees

public final double getBearingDegrees(Position position)

Returns a great circle bearing in degrees in the range 0 to 360.

Parameters:

position -

Returns:

getBearingDifferenceDegrees

public static double getBearingDifferenceDegrees(double bearing1,
                                                 double bearing2)

returns difference in degrees in the range -180 to 180

Parameters:

bearing1 - degrees between -360 and 360

bearing2 - degrees between -360 and 360

Returns:

getDistanceKmToPath

public final double getDistanceKmToPath(Position p1,
                                        Position p2)

calculates the distance of a point to the great circle path between p1 and p2. Formula from: http://www.movable-type.co.uk/scripts/latlong.html

Parameters:

p1 -

p2 -

Returns:

toDegreesMinutesDecimalMinutesLatitude

public static String toDegreesMinutesDecimalMinutesLatitude(double lat)

toDegreesMinutesDecimalMinutesLongitude

public static String toDegreesMinutesDecimalMinutesLongitude(double lon)

assertWithMsg

public static void assertWithMsg(boolean assertion,
                                 String msg)

getPositionAlongPath

public final Position getPositionAlongPath(Position position,
                                           double proportion)

Returns a position along a path according to the proportion value

Parameters:

position -

proportion - is between 0 and 1 inclusive

Returns:

getPositionsAlongPath

public final List<Position> getPositionsAlongPath(Position position,
                                                  double maxSegmentLengthKm)

to360

public final Position to360()

ensureContinuous

public final Position ensureContinuous(Position lastPosition)

normalize the lat lon values of this to ensure that no large longitude jumps are made from lastPosition (e.g. 179 to -180)

Parameters:

lastPosition -

isWithin

public final boolean isWithin(List<Position> positions)

equals

public final boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public final int hashCode()

Overrides:

hashCode in class Object

getDistanceToPathKm

public final double getDistanceToPathKm(List<Position> positions)

getDistanceToSegmentKm

public final double getDistanceToSegmentKm(Position p1,
                                           Position p2)

getClosestIntersectionWithSegment

public final Position getClosestIntersectionWithSegment(Position p1,
                                                        Position p2)

isOutside

public boolean isOutside(List<Position> path,
                         double minDistanceKm)

Parameters:

path -

minDistanceKm -

Returns:

longitudeDiff

public static double longitudeDiff(double a,
                                   double b)

Returns the difference between two longitude values. The returned value is always >=0.

Parameters:

a -

b -

Returns:

to180

public static double to180(double d)

Converts an angle in degrees to range -180< x <= 180.

Parameters:

d -

Returns:

normalizeLongitude

public Position normalizeLongitude()