/*
* Copyright 1998-2014 University Corporation for Atmospheric Research/Unidata
*
* Portions of this software were developed by the Unidata Program at the
* University Corporation for Atmospheric Research.
*
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* any fee or cost, to use, copy, modify, alter, enhance and distribute
* this software, and any derivative works thereof, and its supporting
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package ucar.nc2.dataset.transform;
import ucar.nc2.constants.CF;
import ucar.nc2.dataset.CoordinateTransform;
import ucar.nc2.dataset.ProjectionCT;
import ucar.nc2.dataset.TransformType;
import ucar.nc2.dataset.NetcdfDataset;
import ucar.nc2.Variable;
import ucar.unidata.geoloc.Earth;
/**
* Create a Polar Stereographic Projection from the information in the Coordinate Transform Variable.
*
* @author caron
*/
public class PolarStereographic extends AbstractCoordTransBuilder {
public String getTransformName() {
return CF.POLAR_STEREOGRAPHIC;
}
public TransformType getTransformType() {
return TransformType.Projection;
}
public CoordinateTransform makeCoordinateTransform(NetcdfDataset ds, Variable ctv) {
double lon0 = readAttributeDouble( ctv, CF.STRAIGHT_VERTICAL_LONGITUDE_FROM_POLE, Double.NaN);
if (Double.isNaN(lon0))
lon0 = readAttributeDouble( ctv, CF.LONGITUDE_OF_PROJECTION_ORIGIN, Double.NaN);
if (Double.isNaN(lon0))
throw new IllegalArgumentException("No longitude parameter");
double lat0 = readAttributeDouble( ctv, CF.LATITUDE_OF_PROJECTION_ORIGIN, 90.0);
double latD = 60.0;
double scale = readAttributeDouble( ctv, CF.SCALE_FACTOR_AT_PROJECTION_ORIGIN, Double.NaN);
if (Double.isNaN(scale)) {
double stdpar = readAttributeDouble( ctv, CF.STANDARD_PARALLEL, Double.NaN);
if (!Double.isNaN(stdpar)) {
// caclulate scale snyder (21-7)
// k = 2 * k0/(1 +/- sin stdpar)
// then to make scale = 1 at stdpar, k0 = (1 +/- sin(stdpar))/2
// double sin = Math.sin( Math.toRadians( stdpar));
// scale = (lat0 > 0) ? (1.0 + sin)/2 : (1.0 - sin)/2;
double sin = Math.abs(Math.sin( Math.toRadians( Math.abs(stdpar))));
scale = (1.0 + sin)/2;
latD = stdpar;
} else {
scale = 0.9330127018922193;
}
} else {
// given the scale, calculate stdpar
// k0 = (1 +/- sin(stdpar))/2
// asin(2 * k0 - 1) = stdpar)
double temp = 2 * scale -1;
latD = Math.toDegrees( Math.asin(temp));
}
double false_easting = readAttributeDouble(ctv, CF.FALSE_EASTING, 0.0);
double false_northing = readAttributeDouble(ctv, CF.FALSE_NORTHING, 0.0);
if ((false_easting != 0.0) || (false_northing != 0.0)) {
double scalef = getFalseEastingScaleFactor(ds, ctv);
false_easting *= scalef;
false_northing *= scalef;
}
double earth_radius = getEarthRadiusInKm(ctv);
double semi_major_axis = readAttributeDouble(ctv, CF.SEMI_MAJOR_AXIS, Double.NaN); // meters
double semi_minor_axis = readAttributeDouble(ctv, CF.SEMI_MINOR_AXIS, Double.NaN);
double inverse_flattening = readAttributeDouble(ctv, CF.INVERSE_FLATTENING, 0.0);
ucar.unidata.geoloc.ProjectionImpl proj;
// check for ellipsoidal earth
if (!Double.isNaN(semi_major_axis) && (!Double.isNaN(semi_minor_axis) || inverse_flattening != 0.0)) {
Earth earth = new Earth(semi_major_axis, semi_minor_axis, inverse_flattening);
proj = new ucar.unidata.geoloc.projection.proj4.StereographicAzimuthalProjection(lat0, lon0, scale, latD, false_easting, false_northing, earth);
} else {
proj = new ucar.unidata.geoloc.projection.Stereographic( lat0, lon0, scale, false_easting, false_northing, earth_radius);
}
return new ProjectionCT(ctv.getShortName(), "FGDC", proj);
}
public static void main(String arg[]) {
double stdpar = 70;
double sin = Math.abs(Math.sin( Math.toRadians( stdpar)));
double scale = (1.0 + sin)/2;
System.out.printf("stdpar = %f has scale = %f %n",stdpar, scale );
}
}