AIPS NRAO AIPS HELP file for FRMAP in 31DEC18



As of Mon Oct 15 5:28:41 2018


FRMAP: Task to build a map using fringe rate spectra

INPUTS

USERID                             User number - ignored
INNAME                             Input UV file name (name)
INCLASS                            Input UV file name (class)
INSEQ             0.0     9999.0   Input UV file name (seq. #)
INDISK            0.0        9.0   Input UV file disk unit #
SOURCES                            Source list; The first one is
                                   mapped; if blank =>
                                   the first one in the data.
QUAL            -10.0              Source qualifier -1=>all
CALCODE                            Calibrator code '    '=>all
SELBAND                            Bandwidth to select (kHz)
SELFREQ                            Frequency to select (MHz)
FREQID                             Freq. ID to select. .LE.0 =>1
UVRANGE                            UV range in klambda
                                   0,0 => all baselines
TIMERANG                           Time range to be selected.
                                   1-4 = start day,hr,min,sec
                                   5-8 = end   day,hr,min,sec
                                   0 => timerange of the data
STOKES                             Stokes type to select.
                                   'RR' or 'LL'; '   '=>'RR'
BIF               0.0      100.0   Selected IF number 0=>1
BCHAN             0.0     2048.0   Lowest channel number 0=>all
ECHAN             0.0     2048.0   Highest channel number 0=>all
CHANNEL        -100.0     2048.0   Reference channel number
                                    0 => (bchan + echan)/2
                                   <0 => referencing is not used
SUBARRAY          0.0     1000.0   Subarray, 0=>1
ANTENNAS                           Antennas to select
BASELINE                           Baselines with ANTENNAS
                                   See explanation.
DOCALIB          -1.0      101.0   > 0 calibrate data & weights
                                   > 99 do NOT calibrate weights
GAINUSE                            CL (or SN) table to apply
DOPOL            -1.0       10.0   If >0 correct polarization.
PDVER                              PD table to apply (DOPOL>0)
BLVER                              BL table to apply.
FLAGVER                            Flag table version
DOBAND           -1.0       10.0   If >0 apply bandpass cal.
                                   Method used depends on value
                                   of DOBAND (see HELP file).
BPVER                              Bandpass table version
SMOOTH                             Smoothing function. See
                                   HELP SMOOTH for details.
APARM                              Control information:
                                   1: pre-average interval (sec)
                                      0 => 1/256 of the whole
                                      interval of averaging -
                                      BPARM(3)
                                     -1 => variable depending
                                           upon maximum possible
                                           fringe rate
                                   2: zero padding for FFT
                                        0 =>  no padding
                                        1 =>  N zeroes
                                        2 => 2N zeroes etc.
                                   3: no of frequency channels
                                      to pre-average.
                                   4: step at X-axis,
                                      in mili arcsec.
                                      0 => (X-halfwidth)/50
                                   5: step at Y-axis,
                                      in mili arcsec.
                                      0 => (Y-halfwidth)/50
                                   6: halfwidth of rectangle
                                      on the sky in X-direction;
                                      mili arcsec.
                                      0 => is calculated
                                   7: halfwidth of rectangle
                                      on the sky in Y-direction;
                                      mili arcsec
                                      0 => is calculated
                                   8: Position of rectangle
                                      center in X-direction;
                                      mili arcsec
                                   9: Position of rectangle
                                      center in Y-direction;
                                      mili arcsec
                                  10: 0=> find the solution;
                                      >0 => plot the sets of
                                      lines skiping solution.

BPARM                              More control information:
                                   1: Threshold (in sigmas) in
                                      detection maxima in fringe
                                      rate spectrum.
                                      0 => 4
                                   2: Time interval between
                                      beginnings of interval of
                                      averaging,  minutes
                                      0 => interval in TIMERANG
                                   3: interval of averaging,
                                      minutes
                                      0 => interval in TIMERANG
                                   4: expected accuracy,
                                      mili arcsec
                                      0 => is calculated
                                   5: number of lines plotted
                                      0 => all
                                      -1 => nothing to plot
                                   6: minimum number of lines
                                      for considering crosing
                                      (multiply by NSET).
                                      0 => 0.4(*NSET)
                                   7: number of iterations in
                                      elimination of extra lines
                                      0 => 4
                                   8: Number of lines; criteria
                                      of stop itteration (LINES)
                                      0 => 0.6(*NSET)
                                   9: Level of printing;
                                      0 => minimum
                                      1 => middle
                                      2 => max. See explain.
LTYPE        -410.0       410.0    Type of labeling: 1 border,
                                   2 no ticks, 3 - 6 standard,
                                   7 - 10 only tick labels
                                   <0 -> no date/time
OUTTEXT                            Filename in which the list
                                   of found components is
                                   written.
BADDISK           0.0     9999.0   Disks to avoid for scratch
DOTV           -1.0         1.0    > 0 Do plot on the TV, else
                                   make a plot file
GRCHAN                             Graphics channel;  0 => 1

HELP SECTION

FRMAP
Type:  	Task
Use:   	To create a fringe rate map of the source.
        The data to be used can be selected using a variety of criteria
        e.g. Uvrange, Timerange or by selecting data from  baselines
        determined by the ANTENNAS and BASELINE adverbs. Calibration and
        flagging can be applied to the data before the fringe rate
        mapping. The data can be averaged over a range of frequency
        channels within a given IF as well as over a  time interval.
        The FFT can be optionally padded with zeroes and is computed
        with Hanning weighting.
        The fringe rate spectra can be  calculated after referencing the
        data to a reference frequency channel's data.
        The reference channel should be selected on the basis of
        a simple structure, pointlike or gaussian. It is a good
        idea to use tasks FRPLT or VPLOT  before FRMAP to examine the
        visibilities of all channels to provide a relevant selection of
        the reference channel. Having calculated the fringe rates for
        each SETTIMES (baseline-time) as well as the coefficients of
        sensitivity of the fringe rate to position of a feature in RA(X)
        and declination(Y), we obtain the equations of straight lines
        UDOT*X(I) + VDOT*Y(I) = FR(I) describing the position of
        component I  on the sky. If there is only one component for each
        frequency channel its position is determined by intersection of
        the straight lines set and it can be determined by a least
        square method. Having several components for each frequency
        channel we obtain an ambiguity in the crossing lines.
        The components position can be determined in this case by
        finding the places of highest density of crossing lines.
        (Details can be read in Giuffrida,T.S, 1977 PH.D. thesis MIT;
        and in Walker R.C. Astr. J. v86, 9,1323, 1981). The program
        plots the straight lines on the TV or prepares a plot file.
        Then the program determines the positions of higher density of
        crossing lines. The coordinates in RA and  DEC of the found
        components are written in an output file.

Adverbs:
  USERID.....Input file user number.  Ignored.
  INNAME.....Input UV file name (name).      Standard defaults.
  INCLASS....Input UV file name (class).     Standard defaults.
  INSEQ......Input UV file name (seq. #).    0 => highest.
  INDISK.....Disk drive # of input UV file.  0 => any.
  SOURCES....Source list.  If the data is a multi-source file
             FRMAP will form the map for the first source
             specified. If blank, the first source in the data will
             be mapped. Apparent RA and DEC are taken from SU table.
             If the data is a single source file no source name
             need be specified. Apparent RA and DEC  are colculated.
             The calculation's accuracy is better 10^(-6).
  QUAL.......Only sources with a source qualifier number in the
             SU table matching QUAL will be used if QUAL is not
             -1.
  CALCODE....Calibrators may be selected on the basis of the
             calibrator code:
                  '    ' => any calibrator code selected
                  '*   ' => any non blank code (cal. only)
                  '-CAL' => blank codes only (no calibrators)
                  anything else = calibrator code to select.
             NB: The CALCODE test is applied in addition to the
             other tests, i.e. CALSOUR and QUAL, in the
             selection of sources for which to determine
             solutions.
  SELBAND....Bandwidth of data to be selected. If more than
             one IF is present SELBAND is the width of the
             first IF required. Units = kHz, 0=> all
  SELFREQ....Frequency of data to be selected. If more than
             one IF is present SELFREQ is the frequency of the
             first IF required. Units = MHz, 0=> all
  FREQID.....Frequency identifier to select (you may determine
             which is applicable from the OPTYPE='SCAN' listing
             produced by LISTR. If either SELBAND or SELFREQ
             are set their values overide that of FREQID,
             however setting SELBAND and SELFREQ may occasionally
             result in an ambiguity, in which case the task will
             request that you use FREQID.
  UVRANGE....Range (min, max) of projected baselines to include
             0,0 => all baselines (units: klamda)
  TIMERANG...Time range of the data to be selected. In order:
             Start day, hour, min. sec,
             end day, hour, min. sec. Days relative to ref. date.
             0 => time range of the data
  STOKES.....The desired Stokes type of the output data: ' ' => RR
             'I','V','Q','U','IQU','IQUV','IV','RR','LL','RL',
             'LR','HALF' (=RR,LL), 'FULL' (=RR,LL,RL,LR)
  BIF........Selected IF to map. 0=>1.
             Only one IF can be selected. So EIF is fixed to equal BIF.
  BCHAN......First channel to select. 0=>all.
  ECHAN......Highest channel to select. The channels averaging
             within this channel range is set by APARM(3).
  CHANNEL....CHANNEL sets the reference channel number.
             If CHANNEL = 0 then reference channel number is
             equal (bchan + echan)/2
             If CHANNEL < 0 referencing is not used. This option
             can be used in the case of continuum sources for
             estimating the error of the source coordinates and
             when there is a problem to find a channel with
             simple structure. The time of averaging can be
             limited in this case by frequency unstability of
             local oscilators.
  SUBARRAY...Subarray number to select. 0=>all.
  ANTENNAS...A list of the antennas forming the baselines.
             If any number is negative then all antennas listed
             are NOT to be used and all others are.
  BASELINE...Baselines between antennas named in ANTENNAS and
             those named in BASELINE are selected..
             There are four possible combinations of ANTENNAS
             and BASELINE:
             1. ANTENNAS = 0; BASELINE = 0.
                All possible baselines are selected.
             2. ANTENNAS <>0; BASELINE = 0.
                a)All ANTENNAS > 0
                  Baselines between antennas named in
                  the ANTENNAS list are selected;
                b)Some ANTENNAS < 0
                  Baselines between antennas named in
                  the ANTENNAS list are DE-selected;
             3. ANTENNAS = 0; BASELINE <> 0.
                a)All BASELINE > 0
                  Baselines between antennas named in the
                  BASELINE list and any antenna are selected.
                b)Some BASELINE < 0
                  Baselines between antennas named in the
                  BASELINE list  and any antenna are DE-selected.
             4. ANTENNAS <> 0; BASELINE <> 0.
                a)All ANTENNAS>0; All BASELINE>0
                  Baselines between  antennas named in ANTENNAS
                  and those named in BASELINE are selected.
                b)Some ANTENNAS<0 .OR. Some BASELINE<0
                  Baselines between antennas named in
                  ANTENNAS  and those named in BASELINE
                  are DE-selected.
  DOCALIB....If true (>0), calibrate the data using information in the
             specified Cal (CL) table for multi-source or SN table for
             single-source data.  Also calibrate the weights unless
             DOCALIB > 99 (use this for old non-physical weights).
  GAINUSE....version number of the CL table to apply to
             multisource files or the SN table for single
             source files.  0 => highest.
  DOPOL......If > 0 then correct data for instrumental polarization as
             represented in the AN or PD table.  This correction is
             only useful if PCAL has been run or feed polarization
             parameters have been otherwise obtained.  See HELP DOPOL
             for available correction modes: 1 is normal, 2 and 3 are
             for VLBI.  1-3 use a PD table if available; 6, 7, 8 are
             the same but use the AN (continuum solution) even if a PD
             table is present.
  PDVER......PD table to apply if PCAL was run with SPECTRAL true and
             0 < DOPOL < 6.  <= 0 => highest.
  BLVER......Version number of the baseline based calibration
             (BL) table to appply. <0 => apply no BL table,
             0 => highest.
  FLAGVER....Specifies the version of the flagging table to be
             applied.  0 => highest numbered table.  <0 => no flagging
             to be applied.
  DOBAND.....If true (>0) then correct the data for the shape of the
             antenna bandpasses using the BP table specified by BPVER.
             The correction has five modes:
             (a) if DOBAND=1 all entries for an antenna in the table
             are averaged together before correcting the data.
             (b) if DOBAND=2 the entry nearest in time (including
             solution weights) is used to correct the data.
             (c) if DOBAND=3 the table entries are interpolated in
             time (using solution weights) and the data are then
             corrected.
             (d) if DOBAND=4 the entry nearest in time (ignoring
             solution weights) is used to correct the data.
             (e) if DOBAND=5 the table entries are interpolated in
             time (ignoring solution weights) and the data are then
             corrected.
  BPVER......Specifies the version of the BP table to be
             applied (if DOBAND > 0.
             0 => highest numbered table.
             <0 => no bandpass correction to be applied.
  SMOOTH.....Specifies the type of spectral smoothing to be applied to
             a uv database . The default is not to apply any smoothing.
             The elements of SMOOTH are as follows:
             SMOOTH(1) = type of smoothing to apply: 0 => no smoothing
               To smooth before applying bandpass calibration
                 1 => Hanning, 2 => Gaussian, 3 => Boxcar, 4 => Sinc
               To smooth after applying bandpass calibration
                 5 => Hanning, 6 => Gaussian, 7 => Boxcar, 8 => Sinc
             SMOOTH(2) = the "diameter" of the function, i.e. width
               between first nulls of Hanning triangle and sinc
               function, FWHM of Gaussian, width of Boxcar. Defaults
               (if < 0.1) are 4, 2, 2 and 3 channels for SMOOTH(1) =
               1 - 4 and 5 - 8, resp.
             SMOOTH(3) = the diameter over which the convolving
               function has value - in channels.  Defaults: 1,3,1,4
               times SMOOTH(2) used when input SMOOTH(3) < net
               SMOOTH(2).
  APARM......(1)   sets the pre-average time interval
                   to be used before the FFT. Vector averaging
                   is performed.
                   If APARM(1) = 0 then the pre-average time interval
                   is equal 1/256 of the averaging interval - BPARM(3)
                   IF APARM(1) = -1 then variable pre-average times are
                   calculated for a given set depending upon maximum
                   possible fringe rate. This dynamical change of a pre-
                   average time minimises the computing time but has
                   problem of correct determination of  sigma  because
                   the spectral components occupy the
                   whole spectral window and it complicates determination
                   of the noise. So using dynamical pre-averaging it is
                   useful to decrease the threshold of spectral line
                   discrimination (BPARM(1)). It is recomended to avoid
                   using the dynamical pre-averaging if possible.
                   Number of data points (with unzero weights) in the
                   averaging interval for a given baseline-time has to be
                   more than half of N = BPARM(3)/(pre-avg time).
                   If number of actual data points at the average interval
                   (BPARM(3)) is less than 512 the pre-avg time can be
                   choosen actual pre-avg. time.

             (2)   defines the zero padding to be used in the FFT.
                   0=> no padding; 1=> N zeroes added;
                   2=> 2N zeroes added etc.

             (3)   sets the number of channels to be pre-averaged for
                   each FFT. The channel range over which this averaging
                   takes place is defined by BCHAN and ECHAN.

             (4)   step in X-axis (RA), in milli arcsec.
                   0 => (X-halfwidth)/50

             (5)   step in Y-axis (DEC), in milli arcsec.
                   0 => (Y-halfwidth)/50

             (6)   Halfwidth of rectangle on the sky in X-direction;
                   milli arcsec. 0 => is calculated
                   The  mapping window is limited by rate of change of
                   fringe rate during the  averaging time
                   and as a result the signal is smeared.
                   The smearing is greater for the more
                   distant components. The sizes of the window
                   depend upon the time averaging and the geometry
                   of the interferometers.

             (7)   Halfwidth of rectangle  on the sky in Y-direction;
                   mili arcsec. 0 => is calculated.

             (8)   Position offset of rectangle center in X-direction;
                   in mili arcsec.

             (9)   Position offset of rectangle center in Y-direction;
                   in mili arcsec

             (10)  If zero the program provides both the
                   plotting of the lines' set and the solution for the
                   components by finding the places of highest density
                   of the lines and applying a least square method.
                   If >0 the program provides the plotting of the
                   lines' set only providing opportunity to the user
                   to resolve components himself. This last option
                   saves computing time.

  BPARM......(1)   Threshold (in sigmas) in detection maxima in
                   fringe rate spectrum. 0 => 4. See explanation of
                   APARM(1).

             (2)   Time interval between beginning of each averaging
                   interval,  minutes
                   0 => interval in TIMERANG.

             (3)   Averaging interval, minutes
                   0 => interval in TIMERANG.

             (4)   The map's accuracy used in criteria of terminating
                   of deleting lines in the mapping.
                   mili arcsec. 0 => calculated

             (5)   number of lines plotted.
                   0 => all lines are ploted; -1 => nothing is plotted

             (6)   minimum number of lines for considering
                   crosing (multiply by NSET) a given rectangle.
                   0 => 0.4(*NSET)

             (7)   number of iterations in elimination of extra
                   lines; 0 => 4

             (8)   Number of lines in criteria of itterations stop;
                   If the number of the lines crossing a given
                   rectangular cell is  bigger than this parameter
                   the line giving the biggest deviation from the
                   solution is eliminated. This process is terminated
                   when the number of crossing lines is equal to this
                   parameter (*NSET). 0 => 0.6(*NSET)

             (9)   Level of printing.
                   0 => minimum.
                   The numbers of a current time interval, baseline
                   and channel are printed;
                   1 => medium.
                   In addition to mimimum level the information about
                   rectangular cells with maximum crossing lines is
                   given. So numbers of a set (combination of baseline
                   and time), components, and corresponding fluxes are
                   printed together with coordinates of the rectangular
                   cell and solution for position of the feature are
                   printed.
                   2 => maximum.
                   In addition to medium level equations
                   of lines for each set are printed.

  LTYPE......Labelling type, see HELP LTYPE for details:
             1 = border, 2 = no ticks, 3 or 7 = standard, 4 or 8 =
             relative to ref. pixel, 5 or 9 = relative to subimage
             (BLC, TRC) center, 6 or 10 = pixels.  7-10 all labels
             other than tick numbers and axis type are omitted.
             Less than 0 is the same except that the plot file
             version number and create time are omitted.
             Add n * 100 to alter the metric scaling.
  OUTTEXT....The name of a disk file into which the list of founded
             components is written.
  BADDISK....A list of disks on which scratch files are not to
             be placed.  This will not affect the output file.
  DOTV.......> 0 => plot lines directly on the TV device, otherwise
             make a plot file for later display on one or
             more devices (including the TV if desired).
  GRCHAN.....Graphics channel (1- 7) to use for line drawing.
             0 => 1

EXPLAIN SECTION

FRMAP:  Task to produce the map of the source using the fringe rates.
Documentator:  L.R. Kogan
Related programs:  FRPLT

        Fringe rates are determined precisely using three steps.
        The first one uses criteria of maximum amplitude in the fringe
        rate spectrum and discrimination of the features with amplitu-
        des less than a selected threshold. The value of this threshold
        is equal CO*SIGMA. Sigma is calculated as an average value of
        the spectrum. CO is a coefficient which is selected by BPARM(1).
        A large value of this coefficient can lead to missing some
        features; Small value can produce some false features. The
        compromise for the coefficient is between 2 and 5.
        The second step in fringe rate determination is based on fitting
        amplitudes, fringe rates and phases of features with measured
        visibilities as a function of time. Zero points are excluded
        from the fitting. This exclusion suppress the false maxima
        occured due to lack of data in some time points. The new
        amplitudes of features are compared again with the threshold and
        false maxima are discriminated against.
        The final solution for fringe rates (the third step) is found by
        non linear least square method.
        Having found fringe rates for all given baselines and all given
        times - SETTIMES, the program maps each frequency channel or
        group of pre-averaged channels separately. The selected
        rectangular window in the picture plane (APARM(6) - APARM(9)) is
        devided by number of small rectangular cells. The size of these
        cells is determined by expected angular resolution and can be
        selected by user (APARM(4), APARM(5)) or calculated.
        The program finds the cells which are intersected by the
        number of lines larger than the threshold setting by user. This
        limiting  number of lines = BPARM(6)* SETTIMES, where SETTIMES
        is number of sets (baselines-times) and is recomended to be
        about (0.5 - 1.0)*SETTIMES. If there are several close cells
        intersected by the number of lines larger than the threshold
        then the program finds the cell with maximum number of crossing
        lines (in this cluster of cells) and eliminates the remainder.
        Having found the cells with maximum lines' density the program
        applys least square method to determine the components'
        position. The least square is repeated several times with
        elimination of a line giving maximum deviation from the
        solution on each iteration. The iteration process is terminated
        if the number of crossing lines is  less the selected limit
        BPARM(8), the number of iterations is bigger than a given limit
        BPARM(7), or the given accuracy BPARM(4) is achieved. The final
        list of components found is printed in the ouput file for each
        frequency channel or for each group of preaverage channels.














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