public class Datum extends CrsIdentifiable
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."
Constructor and Description |
---|
Datum(CrsId crsId,
Ellipsoid ellipsoid,
String name,
double[] toWGS84)
Constructs a
Datum . |
Modifier and Type | Method and Description |
---|---|
boolean |
equals(Object o) |
Ellipsoid |
getEllipsoid()
Returns the
Ellipsoid for this Datum |
double[] |
getToWGS84()
Returns the Bursa-Wolf transformation parameters to the WGS84 datum.
|
int |
hashCode() |
getCrsId, getName
public Datum(CrsId crsId, Ellipsoid ellipsoid, String name, double[] toWGS84)
Datum
.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.public Ellipsoid getEllipsoid()
Ellipsoid
for this Datum
public double[] getToWGS84()
If the parameters are not available for this Datum
, than an array of size zero is returned.
public boolean equals(Object o)
equals
in class CrsIdentifiable
public int hashCode()
hashCode
in class CrsIdentifiable
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