next up previous contents index
Next: SOLVE DELAY Up: SOLVE Previous: SOLVE AMPLITUDE   Contents   Index


SOLVE BASELINE

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

    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 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.

    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.

    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.


Gildas manager 2018-05-23