### Version 2.1: Global Doppler implementation

This version is identified by code_version_uvt_dopp = code_version_uvt_v21 = 21:

- 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 mean Doppler factor, equal to , is specified, where is the Geocentric to selected system frame. It is stored in the %gil%dopp variable.
- The source velocity within the selected system frame comes in addition
- u,v coordinates are in a "normal" length, as measured in the geocentric frame. The effective angular resolution is computed from the apparent observing frequency, given by
  (2)
- When merging two UV Tables with different Doppler factor, u,v coordinates are NOT rescaled to a common Doppler factor. Instead a mean Doppler factor is re-computed, and a warning of precision loss given.

In conclusion, v2.1 has precise spectral axis definition, but lousy angular resolution.