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CLIC\TABLE Name [OLD|NEW] [/COMPRESS tmax uvmax]
[/RESAMPLE nc ref val inc code shape width] [/FFT]
[/FREQUENCY name rest-freq] [/DROP n1 n2]
[/NOCHECK [SOURCE|POINTING|PHASE|EPOCH]]
This command will create an UV data Table from the current index. is not
given, the most recently created table will be extended. Next argument
may be OLD (default value if not specified) to extend and existing table,
or NEW to create a new table.
The bands and subbands used must have been given by the command SET SELEC-
TION. The weighting mode can be modified by the command SET WEIGHTS.
TABLE /RESAMPLE nc ref val inc code [shape width /FFT]
Option /RESAMPLE enables to resample data on a new spectral grid (for
line data). 'nc' is the output number of channels, 'ref' the refer-
ence channel, 'val' the value of velocity or frequency offset (with
respect to the rest frequency) at the reference channel, 'inc' the
resolution, 'code' is "V" if the value 'val' and the resolution 'inc'
are in velocity units, "F" for frequency units.
The reference channel thus corresponds to the given 'val' velocity, or
to the offset 'val' in MHz from the rest frequency present in the
header or modified by option /FREQUENCY.
Resampling is done by default through linear interpolation of input
channel data. Resampling may also be done (using option /FFT) in
Fourier space by cut-off or extrapolation (by zeroes) of the Fourier
components, after deconvolution by the channel response of the corre-
lator (due to on-line apodization), and followed by reconvolution to
produce frequency channels of the given 'shape' and 'width'. Allowed
shapes are:
TBox = a box in delay space (unapodized correlator)
Ppar = a parabola in delay space (apodized correlator) (the default)
FBox = a box in frequency space (square filter)
FTri = a triangle in frequency space (Hanning smoothed square fil-
ter)
The width is the channel width in units of channel separation (default
1).
Option /FFT is not recommended when joining together several subbands
to produce a single spectrum, with a limited number of broad channels.
In those cases using the FFT could produce a spectrum with "holes" at
the points between subbands with limited overlap.
TABLE /FREQUENCY name rest-freq
Option /FREQUENCY is used to redefine the rest frequency (in MHz) and
line name for the output table. The velocity scale is computed ac-
cordingly. This rest frequency will correspond to the reference chan-
nel in option RESAMPLE.
TABLE /NOCHECK [SOURCE|POINTING|PHASE|EPOCH]
When processing each scan, CLIC checks whether a number of position
parameters are consistent with those defined in the table header. Op-
tion /NOCHECK allows to switch off this checking. Arguments can be
given to switch off only part of the parameters (SOURCE name, POINTING
direction, PHASE center, EPOCH of coordinates). This option is intend-
ed for building tables with inconsistent parameters (typical exemple
is a different source name...). It is potentially dangerous and is to
be used with caution.
TABLE /DROP n1 n2 --- THIS OPTION IS OBSOLETE
Option /DROP enables to drop the first 'n1' and last 'n2' channels in
each subband of the OLD spectral correlator. For the NEW spectral cor-
relator (data taken since summer 1992), it is replaced by the commands
SET GIBBS and SET DROP.
TABLE /COMPRESS tmax uvmax
Option /COMPRESS is used to compress the data before writing the
table. This works like the COMPRESS command, but no intermediate
file is written. Very seldom used.
Subsections
Gildas manager
2011-09-07