DERIVE Example

          Commands COLLECT and DERIVE are typically used to  improve  wide-band-
    width  self-calibration solutions. At NOEMA, a self-calibration solution can
    be computed independently for each of the 4 Wide band UV table. Assume these
    are stored in Wide-'i'-phase-sol.gdf, with i varying from 1 to 4.
      COLLECT Wide-phase*.gdf Cont-sol.gdf
      DERIVE  Cont-sol.gdf Cont-cgains.uvt
      READ CGAINS Cont-cgains.uvt
      FOR I 1 to 4
        READ UV Wide-'i'.uvt
        APPLY DELAY /FLAG
        WRITE UV Self-Wide-'i'.uvt
      NEXT
    will average the (antenna-based) Phase calibration solutions  (COLLECT)  and
    compute  the corresponding Baseline-based gains (DERIVE).  The loop then ap-
    plies this better self-calibration solution to each UV  table,  scaling  the
    Phases according to Frequency.