Keywords: sic-gdfv2

Next: The new layout Up: UV tables subversions and Previous: Version 2.1: Global Doppler Contents

### Version 2.2: Local Doppler implementation

This version is identified by `code_version_uvt_syst = code_version_uvt_v22 = 22`:

- the frequency given in the spectral axis is also the rest frequency, in the source frame (at the source velocity in the selected system frame)
- the spectral resolution is in that same source frame
- a time dependent Doppler factor, equal to , is specified, where is the Geocentric to selected system frame.
- it is stored in an extra column in the UV Table. This column is identified by `code_uvt_topo`. It can replace one of the 7 mandatory column when in place modification is requested.
- when Doppler variations are small, this column may be absent and in such a case, must be replaced by the global Doppler factor `%gil%dopp`.
- The source velocity within the selected system frame comes in addition
- u,v coordinates are in a "pseudo-normal" length, as measured in the geocentric frame. The effective angular resolution is computed from the apparent observing frequency, given by

  | (3)

- when merging two UV Tables with different Doppler factors, the Doppler column must be propagated, or created from the mean Doppler factors of each table.
- the UV Table header has an observatory section to store the observatory coordinates required to evaluate the Doppler factors. Time and Date are already in the 7 mandatory uv columns.

In conclusion, v2.2 has precise spectral axis definition and precise angular resolution.

Next: The new layout Up: UV tables subversions and Previous: Version 2.1: Global Doppler Contents