Keywords: mapping-noema

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## Multi-Fields UV table

One major step to allow this simplification has been the possibility offered by the GDF UV data format version 2 to allow "extra" columns, i.e. additional data for each visbility. We use it here to store several possible quantities

- column of type `code_uvt_id` contains a real (actually, only integer values are to be found) representing a numerical identification number. This typically handles the field number, for example, but the column type is generic.
- columns of types `code_uvt_loff` and `code_uvt_moff` contain the phase offsets (from the phase center)
- columns of types `code_uvt_xoff` and `code_uvt_yoff` contain the pointing offsets (from the pointing center).

If the phase offset columns are present, but the pointing offset columns are not present, the pointing centers are assumed to be identical to the phase centers. This naturally happens for data taken by all interferometers (NOEMA, ALMA, JVLA, ...).

Subsections

- Importing from UVFITS
- Importing from CLIC
- Importing from separate fields.