org.geolatte.geom.crs

Class Datum

java.lang.Object

org.geolatte.geom.crs.CrsIdentifiable

org.geolatte.geom.crs.Datum

public class Datum
extends CrsIdentifiable

A horizontal datum.

A horizontal datum is the procedure used to measure positions on the surface of the earth (see [CTS-1.00], p. 65).

A Datum has an optional toWGS84 property. If present, this property is a list of up to 7 Bursa Wolf transformation parameters. The meaning of these parameters is described as follows by [CTS-1.00]. "These parameters can be used to approximate a transformation from the horizontal datum to the WGS84 datum. However, it must be remembered that this transformation is only an approximation. For a given horizontal datum, different Bursa Wolf transformations can be used to minimize the errors over different regions. If the DATUM clause contains a TOWGS84 clause, then this should be its "preferred" transformation, which will often be the transformation which gives a broad approximation over the whole area of interest (e.g. the area of interest in the containing geographic coordinate system). Sometimes, only the first three or six parameters are defined. In this case the remaining parameters must be zero. If only three parameters are defined, then they can still be plugged into the Bursa Wolf formulas, or you can take a short cut. The Bursa Wolf transformation works on geocentric coordinates, so you cannot apply it onto geographic coordinates directly. If there are only three parameters then you can use the Molodenski or abridged Molodenski formulas."

Field Summary

Fields

Modifier and Type	Field and Description
private Ellipsoid	ellipsoid
private double[]	toWGS84

Constructor Summary

Constructors

Constructor and Description
Datum(CrsId crsId, Ellipsoid ellipsoid, java.lang.String name, double[] toWGS84) Constructs a Datum.

Method Summary

Modifier and Type	Method and Description
boolean	equals(java.lang.Object o)
Ellipsoid	getEllipsoid() Returns the Ellipsoid for this Datum
double[]	getToWGS84() Returns the Bursa-Wolf transformation parameters to the WGS84 datum.
int	hashCode()

Methods inherited from class org.geolatte.geom.crs.CrsIdentifiable

getCrsId, getName

Methods inherited from class java.lang.Object

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

Field Detail

ellipsoid

private final Ellipsoid ellipsoid

toWGS84

private final double[] toWGS84

Constructor Detail

Datum

public Datum(CrsId crsId,
             Ellipsoid ellipsoid,
             java.lang.String name,
             double[] toWGS84)

Constructs a Datum.

Parameters:

crsId - an identifier for this Datum

ellipsoid - the Ellipsoid for the new Datum

name - the common name for this Datum

toWGS84 - the parameters for the Bursa-Wolf transformation into WGS84.

Method Detail

getEllipsoid

public Ellipsoid getEllipsoid()

Returns the Ellipsoid for this Datum

Returns:

getToWGS84

public double[] getToWGS84()

Returns the Bursa-Wolf transformation parameters to the WGS84 datum.

If the parameters are not available for this Datum, than an array of size zero is returned.

Returns:

the parameters, or an empty array if the parameters are not present.

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class CrsIdentifiable

hashCode

public int hashCode()

Overrides:

hashCode in class CrsIdentifiable