SOLVE BASELINE
Keywords: clic

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SOLVE BASELINE

            CLIC\SOLVE BASELINE [/OFFSET b1 dx1 dy1 dz1 b2  ...]
            [/SEARCH  range  interval]  [/POLYNOMIAL  degree]  [/RESET]  [/PLOT]
        [/SIN]

        This uses a linear method to determine baselines. The  baselines  to  be
        determined  must have been selected by the SET BASELINE command, and the
        data plotted; plot axes must have been previously selected by  :  SET  X
        HOUR_ANGLE  DECLINATION  and SET Y PHASE. With SET ANTENNA in action the
        antenna position offsets are directly fitted to the antenna phases,  en-
        suring baseline closure.

        The  fitting  should  work only if the starting values are within half a
        wavelength in any direction of the true values. Use  option  /OFFSET  to
        correct  the  phases  for  an offset (dx1,dy1,dz1) in baseline b1 before
        fitting.  This is needed if the baseline was wrong by more than  half  a
        wavelength. Offsets are to be given in meters.

        The  results  are  given  as  offsets in  meters  to  be  added  to  the
        baseline  used  for  data  acquisition (which may be read by SIC\EXAMINE
        BASELINE).  The total fitted baseline is also given in meters,  as  well
        as  the  rms  of  the residuals in phase units.  Two sets of offsets are
        given:  the first set (dx, dy, dz) are the offsets with respect  to  the
        antenna  positions actually used, while the secoond set (DX, DY, DZ) are
        with respect to the standard antenna coordinates (the default values  in
        OBS).

        The /SEARCH option  enables  an  automatic  search  with  starting  off-
        sets  scanning a 3-d box in dx, dy, dz, by steps of half a wavelength in
        the three directions.  The arguments range and interval  are  in  meters
        (scanning  is from  -range/2 to +range/2, default -0.005 to 0.005).  On-
        ly the solution with the minimum rms is kept.

        With option /POLYNOMIAL degree, and  if  SET  X  TIME  is  used  in  ad-
        dition  of  HOUR_ANGLE and DECLINATION, a polynomial function of time is
        included in the phase function being fitted.  The degree may range  from
        0 (the default) to 3.  In that case command RESIDUALS will also plot the
        residuals as a function of time.

        The /RESET option resets the solutions in memory.

        The /PLOT option allows to plot the data used for fitting.

        Use command RESIDUALS BASELINE  to  display  the  fit  residuals  (phase
        should be constant). Use later command PRINT BASELINE to create a proce-
        dure file (named CLIC-BASELINE.OBS) containing the antenna position off-
        sets.   This procedure file may be executed by the observing program OBS
        on the control computer bure01.

        If one specify elevation  as  an  additional  X  variable  (e.g.  SET  X
        HOUR_ANGLE  DECLINATION TIME ELEVATION), then an additional parameter is
        fitted: the offsets between elevation and azimuth axes  (or  rather  the
        differences between antennas). These differing offsets result in a phase
        effect proportional to the cosine of elevation. In antenna  mode,  these
        offsets  are  given  for  each antenna in meters. In baseline mode, only
        differences are computed. To further correct for  this  effect  use  the
        command MODIFY AXES. One can optionnaly fit a sinus instead of a cosinus
        in this specific case using option /SIN.