Keywords: mapping-noema

Next: Importing from CLIC Up: Multi-Fields UV table Previous: Multi-Fields UV table Contents

### Importing from UVFITS

To import UVFITS files, some trick is needed because the UVFITS format provided by other packages (mostly CASA) has some specific structure and implicit assumptions that do not map directly to the GILDAS UV data format. Specifically, UVFITS provides for each visibility an ID number corresponding to the source coordinates given in a FITS binary table named "SU".

Thus, importing cannot be done through a simple command, and is done only through the `fits_to_uvt.map` script The UV table is temporarily created with two additional columns, one of which is holding the source ID number, and after the SU Table is read, these two columns are filled with the phase offset centers, and labelled of type `code_uvt_loff` and `code_uvt_moff` respectively. As UVFITS provides absolute coordinates, and not offset, the first field center is arbitrarily taken as the reference for offsets. This may change for a more convenient value (e.g. the centroid) later. If only one field is found, the columns are simply labelled as type `code_uvt_id` so that they remain ignored in any further processing.

NOTE: the UVFITS format allows for cases where the SU tables also provide pointing centers. So far, this has not been implemented in any known FITS writer, and CASA does not support this possibility. However, once GILDAS UV tables have been converted to a common phase center (Mosaic UV tables with only pointing offsets, see below), this possibility may be required to export simply the data into UVFITS format for archival. The current code does not allow this yet.

Next: Importing from CLIC Up: Multi-Fields UV table Previous: Multi-Fields UV table Contents