/**
* Converts grid-relative wind to true (or absolute) wind. The U and V components of true wind are
* {@link WesterlyWind} and {@link SoutherlyWind}, respectively. The domain of the input {@link
* visad.FlatField} must have a manifold dimension of two or greater and it must have a reference
* system which contains {@link visad.RealType#Latitude} and {@link visad.RealType#Longitude}. The
* number of components in the range of the input {@link visad.FlatField} must be two. Both
* components must have units convertible with {@link #DEFAULT_SPEED_UNIT}. The first and second
* components are assumed to be the wind components in the direction of increasing first and
* second manifold dimension indexes, respectively. The {@link visad.MathType} of the range of the
* returned {@link visad.FlatField} will be <code>CartesianHorizontalWind.getEarthVectorType()
* </code> and the domain will be the same as the input domain.
*
* @param rel The field of grid-relative wind.
* @return The field of true wind corresponding to the input field.
* @throws NullPointerException if <code>rel</code> is <code>null</code>.
* @throws IllegalArgumentException if the input field doesn't have two and only two components in
* its range, or if the default units of the input range aren't equal, or if the domain of the
* input field doesn't have a transformation to latitude and longitude, or the grid is
* irregular or has too few points.
* @throws VisADException if a VisAD failure occurs.
* @throws RemoteException if a Java RMI failure occurs.
* @see CartesianHorizontalWind
*/
public static FlatField cartesianHorizontalWind(FlatField rel)
throws VisADException, RemoteException {
FunctionType funcType = (FunctionType) rel.getType();
MathType rangeType = funcType.getRange();
if (rel.getRangeDimension() != 2) {
throw new IllegalArgumentException(rangeType.toString());
}
Unit[] units = rel.getDefaultRangeUnits();
if (!units[0].equals(units[1])) {
throw new IllegalArgumentException(units.toString());
}
SampledSet grid = (SampledSet) rel.getDomainSet();
// check for single point grid
if (grid instanceof SingletonSet) {
return rel;
} else if (grid instanceof GriddedSet) {
int[] lengths = ((GriddedSet) grid).getLengths();
if ((lengths[0] == 1) && (lengths[1] == 1)) {
return rel;
}
}
FlatField abs =
new FlatField(
new FunctionType(funcType.getDomain(), CartesianHorizontalWind.getEarthVectorType()),
grid,
(CoordinateSystem[]) null,
rel.getRangeSets(),
units);
abs.setSamples(trueWind(rel.getFloats(), grid), false);
return abs;
}
