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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
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.