private void extractCoordinateSystem() throws TransformationException {

    // To get the coordinate system we look at the CTYPEn, EQUINOX, RADESYSm

    String lonType = h.getStringValue("CTYPE" + lonAxis).substring(0, 4);
    String latType = h.getStringValue("CTYPE" + latAxis).substring(0, 4);
    String coordSym = null;

    CoordinateSystem coords;

    if (lonType.equals("RA--") && latType.equals("DEC-")) {
      coordSym = frame() + equinox();
    } else {
      if (lonType.charAt(0) != latType.charAt(0)) {
        throw new TransformationException(
            "Inconsistent axes definitions:" + lonType + "," + latType);
      }

      if (lonType.equals("GLON")) {
        coordSym = "G";
      } else if (lonType.equals("ELON")) {
        coordSym = "E" + equinox();
      } else if (lonType.equals("HLON")) {
        coordSym = "H" + equinox();
      }
    }

    coords = CoordinateSystem.factory(coordSym);
    this.csys = coords;

    add(coords.getSphereDistorter());
    add(coords.getRotater());
  }
  /** Handle the NEAT special projection */
  private void doNeatWCS() throws TransformationException {

    // The NEAT transformation from the standard spherical system
    // includes:
    //   Transformation to J2000 spherical coordinates (a null operation)
    //   A tangent plane projection to the standard plane
    //   A scaler transformation to corrected pixel coordinates.
    //   A distorter to distorted pixel coordinates
    //   A scaler transformation of distorted coordinates to actual pixels

    CoordinateSystem csys = CoordinateSystem.factory("J2000");
    this.csys = csys;

    // The RA0/DEC0 pair are the actual center of the projection.

    double cv1 = toRadians(h.getDoubleValue("RA0"));
    double cv2 = toRadians(h.getDoubleValue("DEC0"));
    wcsKeys.put("CRVAL1", toDegrees(cv1));
    wcsKeys.put("CRVAL2", toDegrees(cv2));

    Projection proj = new Projection("Tan", new double[] {cv1, cv2});
    this.proj = proj;

    double cd1 = toRadians(h.getDoubleValue("CDELT1"));
    double cd2 = toRadians(h.getDoubleValue("CDELT2"));
    wcsKeys.put("CDELT1", toDegrees(cd1));
    wcsKeys.put("CDELT2", toDegrees(cd2));

    wcsScale = abs(cd1);

    double cp1 = h.getDoubleValue("CRPIX1");
    double cp2 = h.getDoubleValue("CRPIX2");

    wcsKeys.put("CPRIX1", cp1);
    wcsKeys.put("CRPIX2", cp2);

    wcsKeys.put("CTYPE1", "RA---XTN");
    wcsKeys.put("CTYPE2", "DEC--XTN");

    Scaler s1 = new Scaler(0., 0., -1 / cd1, 0, 0, -1 / cd2);

    // Note that the the A0,A1,A2, B0,B1,B2 rotation
    // is relative to the original pixel values, so
    // we need to put this in the secondary scaler.
    //
    double x0 = h.getDoubleValue("X0");
    double y0 = h.getDoubleValue("Y0");

    Distorter dis =
        new skyview.geometry.distorter.Neat(
            h.getDoubleValue("RADIAL"), h.getDoubleValue("XRADIAL"), h.getDoubleValue("YRADIAL"));

    double a0 = h.getDoubleValue("A0");
    double a1 = h.getDoubleValue("A1");
    double a2 = h.getDoubleValue("A2");
    double b0 = h.getDoubleValue("B0");
    double b1 = h.getDoubleValue("B1");
    double b2 = h.getDoubleValue("B2");

    // The reference pixel is to be computed in the distorted frame.
    double[] cpix = new double[] {cp1, cp2};
    double[] cout = new double[2];
    dis.transform(cpix, cout);
    Scaler s2 =
        new Scaler(
            cout[0] - a0 - a1 * x0 - a2 * y0,
            cout[1] - b0 - b2 * x0 - b1 * y0,
            -(1 + a1),
            -a2,
            -b2,
            -(1 + b1));

    wcsKeys.put("A0", a0);
    wcsKeys.put("A1", a1);
    wcsKeys.put("A2", a2);
    wcsKeys.put("B0", b0);
    wcsKeys.put("B1", b1);
    wcsKeys.put("B2", b2);

    this.distort = dis;
    add(csys.getSphereDistorter());
    add(csys.getRotater());
    add(proj.getRotater());
    add(proj.getProjecter());
    this.scale = s1;
    // Note that s1 is defined from the projection plane to the pixels coordinates,
    // so we don't need to invert it.
    //
    // But the second scaler, s2,  used in the NEAT correction
    // is defined in the direction from pixels to sphere, so we
    // need to take its inverse.
    this.scale = this.scale.add(s2.inverse());
    add(this.scale);
    add(dis);
  }
  /** Handle a DSS projection */
  private void doDSSWCS() throws TransformationException {

    double plateRA =
        h.getDoubleValue("PLTRAH")
            + h.getDoubleValue("PLTRAM") / 60
            + h.getDoubleValue("PLTRAS") / 3600;
    plateRA = toRadians(15 * plateRA);
    wcsKeys.put("PLTRAH", h.getDoubleValue("PLTRAH"));
    wcsKeys.put("PLTRAM", h.getDoubleValue("PLTRAM"));
    wcsKeys.put("PLTRAS", h.getDoubleValue("PLTRAS"));

    double plateDec =
        h.getDoubleValue("PLTDECD")
            + h.getDoubleValue("PLTDECM") / 60
            + h.getDoubleValue("PLTDECS") / 3600;
    plateDec = toRadians(plateDec);

    if (h.getStringValue("PLTDECSN").substring(0, 1).equals("-")) {
      plateDec = -plateDec;
    }
    wcsKeys.put("PLTDECD", h.getDoubleValue("PLTDECD"));
    wcsKeys.put("PLTDECM", h.getDoubleValue("PLTDECM"));
    wcsKeys.put("PLTDECS", h.getDoubleValue("PLTDECS"));
    wcsKeys.put("PLTDECSN", h.getStringValue("PLTDECSN"));

    double plateScale = h.getDoubleValue("PLTSCALE");
    double xPixelSize = h.getDoubleValue("XPIXELSZ");
    double yPixelSize = h.getDoubleValue("YPIXELSZ");
    wcsKeys.put("PLTSCALE", plateScale);
    wcsKeys.put("XPIXELSZ", xPixelSize);
    wcsKeys.put("YPIXELSZ", yPixelSize);

    double[] xCoeff = new double[20];
    double[] yCoeff = new double[20];

    for (int i = 1; i <= 20; i += 1) {
      xCoeff[i - 1] = h.getDoubleValue("AMDX" + i);
      yCoeff[i - 1] = h.getDoubleValue("AMDY" + i);
      wcsKeys.put("AMDX" + i, xCoeff[i - 1]);
      wcsKeys.put("AMDY" + i, yCoeff[i - 1]);
    }

    double[] ppo = new double[6];
    for (int i = 1; i <= 6; i += 1) {
      ppo[i - 1] = h.getDoubleValue("PPO" + i);
      wcsKeys.put("PPO" + i, ppo[i - 1]);
    }

    double plateCenterX = ppo[2];
    double plateCenterY = ppo[5];

    double cdelt1 = -plateScale / 1000 * xPixelSize / 3600;
    double cdelt2 = plateScale / 1000 * yPixelSize / 3600;

    wcsScale = abs(cdelt1);

    // This gives cdelts in degrees per pixel.

    // CNPIX pixels use a have the first pixel going from 1 - 2 so they are
    // off by 0.5 from FITS (which in turn is offset by 0.5 from the internal
    // scaling, but we handle that elsewhere).
    double crpix1 = plateCenterX / xPixelSize - h.getDoubleValue("CNPIX1", 0) - 0.5;
    double crpix2 = plateCenterY / yPixelSize - h.getDoubleValue("CNPIX2", 0) - 0.5;
    wcsKeys.put("CNPIX1", h.getDoubleValue("CNPIX1", 0));
    wcsKeys.put("CNPIX2", h.getDoubleValue("CNPIX2", 0));

    Projection proj = new Projection("Tan", new double[] {plateRA, plateDec});
    this.proj = proj;
    CoordinateSystem coords = CoordinateSystem.factory("J2000");
    this.csys = coords;

    cdelt1 = toRadians(cdelt1);
    cdelt2 = toRadians(cdelt2);

    Scaler s = new Scaler(-cdelt1 * crpix1, -cdelt2 * crpix2, cdelt1, 0, 0, cdelt2);

    // Got the transformers ready.  Add them in properly.
    add(coords.getSphereDistorter());
    add(coords.getRotater());
    add(proj.getRotater());
    add(proj.getProjecter());

    this.distort =
        new skyview.geometry.distorter.DSS(
            plateRA, plateDec, xPixelSize, yPixelSize, plateScale, ppo, xCoeff, yCoeff);
    add(this.distort);

    this.scale = s.inverse();

    add(this.scale);
  }