/// <summary>
/// Handles WCS calculations based on CROTA2, CDELT and tangential projection
/// </summary>
/// <param name="crval1">Reference x pixel value</param>
/// <param name="crval2">Reference y pixel value</param>
/// <param name="crpix1">Reference pixel x</param>
/// <param name="crpix2">Reference pixel y</param>
/// <param name="cdelta1">per pixel increment along RA</param>
/// <param name="cdelta2">per pixel increment along DEC</param>
/// <param name="crota2">Rotation in degrees</param>
/// <remarks>Vertically and horizontally flipped images don't work as of now</remarks>
public WorldCoordinateSystem(
double crval1,
double crval2,
double crpix1,
double crpix2,
double cdelta1,
double cdelta2,
double crota2
)
{
Point = new Point(crpix1, crpix2);
Coordinates = new Coordinates(Angle.ByDegree(crval1), Angle.ByDegree(crval2), Epoch.J2000);
if (cdelta1 >= 0 || cdelta2 < 0)
{
Flipped = true;
}
if (!Flipped)
{
Rotation = Astrometry.EuclidianModulus(crota2, 360);
}
else
{
Rotation = Astrometry.EuclidianModulus(-crota2, 360);
}
PixelScaleX = Astrometry.DegreeToArcsec(Math.Abs(cdelta1));
PixelScaleY = Astrometry.DegreeToArcsec(Math.Abs(cdelta2));
}
/// <summary>
/// Handles WCS calculations based on CDn_m matrix and tangential projection
/// </summary>
/// <param name="crval1">Reference x pixel value</param>
/// <param name="crval2">Reference y pixel value</param>
/// <param name="crpix1">Reference pixel x</param>
/// <param name="crpix2">Reference pixel y</param>
/// <param name="cd1_1">CDn_m tranformation matrix</param>
/// <param name="cd1_2">CDn_m tranformation matrix</param>
/// <param name="cd2_1">CDn_m tranformation matrix</param>
/// <param name="cd2_2">CDn_m tranformation matrix</param>
/// <remarks>
/// http://hosting.astro.cornell.edu/~vassilis/isocont/node17.html
/// https://www.astro.rug.nl/~gipsy/tsk/fitsreproj.dc1
/// Vertically and horizontally flipped images don't work as of now
/// </remarks>
public WorldCoordinateSystem(
double crval1,
double crval2,
double crpix1,
double crpix2,
double cd1_1,
double cd1_2,
double cd2_1,
double cd2_2
)
{
Point = new Point(crpix1, crpix2);
Coordinates = new Coordinates(Angle.ByDegree(crval1), Angle.ByDegree(crval2), Epoch.J2000);
var determinant = cd1_1 * cd2_2 - cd1_2 * cd2_1;
var sign = 1;
if (determinant < 0)
{
sign = -1;
}
var cdelta1 = sign * Math.Sqrt(cd1_1 * cd1_1 + cd2_1 * cd2_1);
var cdelta2 = Math.Sqrt(cd1_2 * cd1_2 + cd2_2 * cd2_2);
if (cdelta1 >= 0 || cdelta2 < 0)
{
Flipped = true;
}
var rot1_cd = Math.Atan2(sign * cd1_2, cd2_2);
var rot2_cd = Math.Atan2(sign * cd1_1, cd2_1) - Math.PI / 2d;
var rotation = Astrometry.ToDegree(Flipped ? -rot2_cd : rot2_cd);
var skew = Astrometry.ToDegree(Math.Abs(rot1_cd - rot2_cd));
//Approximation as the matrix can account for skewed axes
Rotation = Astrometry.EuclidianModulus(rotation, 360);
PixelScaleX = Astrometry.DegreeToArcsec(Math.Abs(cdelta1));
PixelScaleY = Astrometry.DegreeToArcsec(Math.Abs(cdelta2));
}