Skip to main content
`Ctrl`+`K`

# Supported projections

As `astropy.wcs` is based on wcslib, it supports the standard projections defined in the FITS WCS standard. These projection codes are three letter strings specified in the second part of the `CTYPEn` keywords (accessible through `Wcsprm.ctype`). For example, a tangent projection with RA, DEC coordinates is defined by `CTYPE1 = RA---TAN` and `CTYPE2 = DEC--TAN`. If a SIP distortion is present the keywords become `CTYPE1 = RA---TAN-SIP` and `CTYPE2 = DEC--TAN-SIP`.

The supported projection codes are:

- `AZP`: zenithal/azimuthal perspective

- `SZP`: slant zenithal perspective

- `TAN`: gnomonic

- `STG`: stereographic

- `SIN`: orthographic/synthesis

- `ARC`: zenithal/azimuthal equidistant

- `ZPN`: zenithal/azimuthal polynomial

- `ZEA`: zenithal/azimuthal equal area

- `AIR`: Airy’s projection

- `CYP`: cylindrical perspective

- `CEA`: cylindrical equal area

- `CAR`: plate carrée

- `MER`: Mercator’s projection

- `COP`: conic perspective

- `COE`: conic equal area

- `COD`: conic equidistant

- `COO`: conic orthomorphic

- `SFL`: Sanson-Flamsteed (“global sinusoid”)

- `PAR`: parabolic

- `MOL`: Mollweide’s projection

- `AIT`: Hammer-Aitoff

- `BON`: Bonne’s projection

- `PCO`: polyconic

- `TSC`: tangential spherical cube

- `CSC`: COBE quadrilateralized spherical cube

- `QSC`: quadrilateralized spherical cube

- `HPX`: HEALPix

- `XPH`: HEALPix polar, aka “butterfly”

And, if built with wcslib 5.0 or later, the following polynomial distortions are supported:

- `TPV`: Polynomial distortion

- `TUV`: Polynomial distortion

Note

Though wcslib 5.4 and later handles `SIP` polynomial distortion, for backward compatibility, `SIP` is handled by astropy itself and methods exist to handle it specially.