GWCS

class snappl.wcs.GWCS(gwcs=None)[source]

Bases: BaseWCS

A “G” (Generalized?) WCS : https://gwcs.readthedocs.io/en/latest/

In the current code, these are only read from roman datamodel ASDF files

Methods Summary

from_adsf(asdf_file)

Load the WCS from the specified ASDF image file.

get_astropy_wcs([readonly, degree])

Return an astropy.wcs.WCS object, if possible.

pixel_to_world(x, y)

Go from (x, y) coordinates to ICRS (ra, dec)

world_to_pixel(ra, dec)

Go from (ra, dec) coordinates to (x, y)

Methods Documentation

classmethod from_adsf(asdf_file)[source]

Load the WCS from the specified ASDF image file. (Also see RomanDatamodelImage.get_wcs.)

get_astropy_wcs(readonly=True, degree=5)[source]

Return an astropy.wcs.WCS object, if possible.

Parameters:

  • readonly (bool, default True) – If True, you are promising not to modify the WCS you get back! If you’re going to modify it, set readonly to False. (For some subclasses, this doesn’t actually change behavior.)

  • degree (int) – The degree of the astropy WCS used to approximate the WCS in the object. The default is subclass-dependent. Ignored by some subclasses.

For some subclasses, this astropy.wcs.WCS may only be an approximation of the true WCS represented by the object.

pixel_to_world(x, y)[source]

Go from (x, y) coordinates to ICRS (ra, dec)

Parameters:

  • x (float or sequence of float) – The x position on the image. The center of the lower-left pixel is at x=0.0

  • y (float or sequence of float) – The y position on the image. The center of the lower-left pixle is y=0.0

Returns:

  • ra, dec (floats or arrays of floats, decimal degrees)

  • You will get back two floats if x an y were floats. If x and

  • y were lists (or other sequences), you will get back two numpy

  • arrays of floats.

world_to_pixel(ra, dec)[source]

Go from (ra, dec) coordinates to (x, y)

Parameters:

  • ra (float or sequence of float) – RA in decimal degrees

  • dec (float or sequence of float) – Dec in decimal degrees

Returns:

  • x, y (floats or arrays of floats)

  • Pixel position on the image; the center of the lower-left pixel is (0.0, 0.0).

  • If ra and dec were floats, x and y are floats. If ra and dec

  • were sequences of floats, x and y will be numpy arrays of floats.