Next: Dap positions and size
Up: The new layout
Previous: The new layout
Contents
UV Tables are now a special subset of GDF files. As any GDF file, they are
identified by an integer code stored in variable h%gil%type_gdf
(see Table 2) which, for UV Tables must take the value
code_gdf_uvt or code_gdf_tuv, depending whether the
table is in native order (a visibility being contiguous in memory) or
transposed. For simplicity, we have imposed code_gdf_tuv =
-code_gdf_uvt.
The new layout differs in several ways from the older one. In short:
- The daps are no longer at pre-defined positions in the data
file, but their positions are described by the UV table header (cf. the
following section for details).
- The complex visibility elements are not necessarily (real,
imaginary, weight) triplets, but contain h%gil%natom
elements. For example, a zero spacing UV table from a single-dish
spectrum may have h%gil%natom = 2 (as the imaginary part is 0
in such a case).
- Provision is made to handle polarization data, by indicating the
number of Stokes parameters in a visibility, h%gil%nstokes.
- The number of frequency channels h%gil%nchan and
the number of visibilities h%gil%nvisi are available
independently of the transposition status of the UV data set.
The UV specific information is included in the uvda section of the
h%gil header, as described in appendix B.
Next: Dap positions and size
Up: The new layout
Previous: The new layout
Contents
Gildas manager
2015-03-01