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/*
 * Copyright (c) 1998-2018 John Caron and University Corporation for Atmospheric Research/Unidata
 * See LICENSE for license information.
 */

package ucar.nc2.dataset.transform;

import ucar.nc2.AttributeContainer;
import ucar.nc2.constants.CF;
import ucar.nc2.dataset.ProjectionCT;

/**
 * Create a Mercator Projection from the information in the Coordinate Transform Variable.
 *
 * @author caron
 */
public class Mercator extends AbstractTransformBuilder implements HorizTransformBuilderIF {

  @Override
  public String getTransformName() {
    return CF.MERCATOR;
  }

  @Override
  public ProjectionCT makeCoordinateTransform(AttributeContainer ctv, String geoCoordinateUnits) {
    double par = readAttributeDouble( ctv, CF.STANDARD_PARALLEL, Double.NaN);
    if (Double.isNaN(par)) {
      double scale = readAttributeDouble( ctv, CF.SCALE_FACTOR_AT_PROJECTION_ORIGIN, Double.NaN);
      if (Double.isNaN(scale))
        throw new IllegalArgumentException("Mercator projection must have attribute " +
                CF.STANDARD_PARALLEL + " or " + CF.SCALE_FACTOR_AT_PROJECTION_ORIGIN);
      par = ucar.unidata.geoloc.projection.Mercator.convertScaleToStandardParallel(scale);
    }

    readStandardParams(ctv, geoCoordinateUnits);

    ucar.unidata.geoloc.projection.Mercator proj =
            new ucar.unidata.geoloc.projection.Mercator( lon0, par, false_easting, false_northing, earth_radius);
    return new ProjectionCT(ctv.getName(), "FGDC", proj);
  }
}