Package org.osgi.util.position

Class Position

java.lang.Object

org.osgi.util.position.Position

public class Position
extends java.lang.Object

Position represents a geographic location, based on the WGS84 System (World Geodetic System 1984).

The org.osgi.util.measurement.Measurement class is used to represent the values that make up a position.

A given position object may lack any of it's components, i.e. the altitude may not be known. Such missing values will be represented by null.

Position does not override the implementation of either equals() or hashCode() because it is not clear how missing values should be handled. It is up to the user of a position to determine how best to compare two position objects. A Position object is immutable.

Field Summary

Fields

Modifier and Type	Field	Description
private Measurement	altitude
private static double	LAT_RANGE
private Measurement	latitude
private static double	LON_RANGE
private Measurement	longitude
private Measurement	speed
private Measurement	track
private static double	TRACK_RANGE

Constructor Summary

Constructors

Constructor	Description
Position(Measurement lat, Measurement lon, Measurement alt, Measurement speed, Measurement track)	Constructs a Position object with the given values.

Method Summary

Modifier and Type	Method	Description
Measurement	getAltitude()	Returns the altitude of this position in meters.
Measurement	getLatitude()	Returns the latitude of this position in radians.
Measurement	getLongitude()	Returns the longitude of this position in radians.
Measurement	getSpeed()	Returns the ground speed of this position in meters per second.
Measurement	getTrack()	Returns the track of this position in radians as a compass heading.
private static double	normalize(double value, double range)	This function normalizes the a value according to a range.

Methods inherited from class java.lang.Object

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

Field Detail

altitude

private final Measurement altitude

longitude

private final Measurement longitude

latitude

private final Measurement latitude

speed

private final Measurement speed

track

private final Measurement track

LON_RANGE

private static final double LON_RANGE

See Also:

Constant Field Values

LAT_RANGE

private static final double LAT_RANGE

See Also:

Constant Field Values

TRACK_RANGE

private static final double TRACK_RANGE

See Also:

Constant Field Values

Constructor Detail

Position

public Position(Measurement lat,
                Measurement lon,
                Measurement alt,
                Measurement speed,
                Measurement track)

Constructs a Position object with the given values.

Parameters:

lat - a Measurement object specifying the latitude in radians, or null

lon - a Measurement object specifying the longitude in radians, or null

alt - a Measurement object specifying the altitude in meters, or null

speed - a Measurement object specifying the speed in meters per second, or null

track - a Measurement object specifying the track in radians, or null

Method Detail

getAltitude

public Measurement getAltitude()

Returns the altitude of this position in meters.

Returns:

a Measurement object in Unit.m representing the altitude in meters above the ellipsoid null if the altitude is not known.

getLongitude

public Measurement getLongitude()

Returns the longitude of this position in radians.

Returns:

a Measurement object in Unit.rad representing the longitude, or null if the longitude is not known.

getLatitude

public Measurement getLatitude()

Returns the latitude of this position in radians.

Returns:

a Measurement object in Unit.rad representing the latitude, or null if the latitude is not known..

getSpeed

public Measurement getSpeed()

Returns the ground speed of this position in meters per second.

Returns:

a Measurement object in Unit.m_s representing the speed, or null if the speed is not known..

getTrack

public Measurement getTrack()

Returns the track of this position in radians as a compass heading. The track is the extrapolation of previous previously measured positions to a future position.

Returns:

a Measurement object in Unit.rad representing the track, or null if the track is not known..

normalize

private static double normalize(double value,
                                double range)

This function normalizes the a value according to a range. This is not simple modulo (as I thought when I started), but requires some special handling. For positive numbers we subtract 2*range from the number so that end up between -/+ range. For negative numbers we add this value. For example, if the value is 270 and the range is +/- 180. Then sign=1 so the (int) factor becomes 270+180/360 = 1. This means that 270-360=-90 is the result. (degrees are only used to make it easier to understand, this function is agnostic for radians/degrees). The result will be in [range,range> The algorithm is not very fast, but it handling the [> ranges made it very messy using integer arithmetic, and this is very readable. Note that it is highly unlikely that this method is called in normal situations. Normally input values to position are already normalized because they come from a GPS. And this is much more readable.

Parameters:

value - The value that needs adjusting

range - -range = < value < range