### Direct compatibility

A number of projections defined in the AIPS memos are fully compatible with the new CG02 formalism, which allows an immediate compatibility of the GILDAS projections with the FITS files. According to the CG02 section 6.1.1, The SIN [orthographic] projection defined by Greisen (1983) is here generalized by the addition of projection parameters. However, these parameters assume default values which reduce to the simple orthographic projection of the AIPS convention. Therefore no translation is required. And in their section 6.1.3, The TAN [gnomonic], ARC [azimuthal] and STG [stereographic] projections defined by Greisen (1983, 1986) are directly equivalent to those defined here and no translation is required.