SOLVE BASELINE

 

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

    This uses a linear method  to   determine   baselines   separately   and
    should  work only if the starting values are within half a wavelength in
    any direction of the true values.  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.

    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
    offsets  scanning a 3-d box in dx, dy, dz, by steps of half a wavelength
    in the three directions.  The argument range is in meters  (scanning  is
    from  -range/2 to +range/2, default -0.005 to 0.005).  Only the solution
    with the minimum rms is kept.  Searching one baseline in  a  0.01  meter
    range takes 4 seconds on the micro-vax 3400.

    Use command RESIDUALS BASELINE to  display  the  fit  residuals   (phase
    should be constant).

    With SET  ANTENNA  in  action   the   antenna   position   offsets   are
    directly fitted to the antenna phases, ensuring baseline closure.

    Use later command PRINT BASELINE to  create  a  procedure  file   (named
    CLIC-BASELINE.OBS)   containing  the  antenna  position  offsets.   This
    procedure file may be executed by  the  observing  program  OBS  on  the
    control computer BURE01.

    With option /POLYNOMIAL degree, and  if  SET   X   TIME   is   used   in
    addition 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.

    In 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.  It  is
    foreseen  to  correct  for this effect in real time, when the values are
    well and unambiguously known.