Private parameters for program NFLAG
This document contains an overview of the parameter interface of the program NFLAG. The program also uses a number of public interfaces; references to these are also listed.
The remainder of the document describes the individual parameters in alphabetical order. This description centers on the Help texts, which have been designed to guide the user to the proper choice at each junction, even if his knowledge of the overall workings of the program is only superficial.
See also:
Prompt: Acceptance range for ABS(cos), ABS(sin)
Expected input: Real: 1 to 2 values
An ENTIRE scan will be flagged if for any valid data point in it
the modulus of either the real (cos) or imaginary (sin) part falls outside the
acceptance range.
This option allows you to reject scans containing interference peaks, or 'bad' data (i.e. abnormally low amplitudes).
NOTES:
The new setting of the target flag in each scan or data point will
OVERRIDE the current one rather than being ORed into it.
The flags used in selecting valid scans are defined by parameter ?
SELECT_FLAGS; the default is ALL.
see parameters DRY_SCANS,
SELECT_FLAG
NB: When new thresholds are given, all Scans in the specified data cube are (un-)flagged accordingly, including the Scans that were flagged already.
Prompt: Clip threshold (W.U.)
Expected input: Real: 1 value
Specify the threshold value (W.U.) for the clipping criterion
selected.
The default value shown is three times the rms value calculated in a 'trial run' through the first <N> valid (see Note below) scans in the primary/secondary data cube. This is intended to be an educated guess at a sensible 3-sigma threshold for your operation, but you must make your own assessment of the probable suitability of this value.
Notes:
The new setting of the target flag in each scan or data point will
OVERRIDE the current one rather than being ORed into it.
The number <N> of dry-run scans is defined by the parameter DRY_SCANS; the
default is 25.
The flags used in selecting valid scans are defined by parameter ?
SELECT_FLAGS; the default is ALL.
see parameters DRY_SCANS,
SELECT_FLAG
Prompt: Clip limits
Expected input: Real: 1 to 2 values
Specify the range within which the test value will be accepted.
For values outside the range the flag will be set, for those within the range
it will be cleared.
The default value shown is three times the rms value calculated in a 'trial run' through the first <N> valid (see Note below) scans in the primary/secondary data cube. This is intended to be an educated guess at a sensible 3-sigma threshold for your operation, but you must make your own assessment of the probable suitability of this value.
Notes:
The new setting of the target flag in each scan or data point will
OVERRIDE the current one rather than being ORed into it.
The number <N> of dry-run scans is defined by the parameter DRY_SCANS; the
default is 25.
The flags used in selecting valid scans are defined by parameter ?
SELECT_FLAGS; the default is ALL.
see parameters DRY_SCANS,
SELECT_FLAG
Prompt: Number of scans to use in trial runs
Expected input: Integer: 1 value
'Clipping' operations need (a) threshold value(s) that is (are) related to the magnitude of the data at hand.
The program determines a 'rasonable' default for such cases by performing a 'trial run' on the first of the scans in the data cube selected. You may specify their number here. The trial run evaluates the clipping criterion but does NOT modify the .SCN file. For data with reasonably stationary statistics, the default number should be adequate. A larger number obviously will take more time to process. If you specify a very large number, the trial run will include the entire data cube selected.
Prompt: Discontinuity threshold (W.U. per 10 sec)
Expected input: Real: 1 value
The DT1 option looks for 'un-physical jumps' in time in the
cosine and sine values of the uv-data. The actual difference (in W.U.) between
successive time-samples is divided by the time that separates them, in units of
the integration time (e.g. 60 sec). The flag is set if this value exceeds the
threshold.
Prompt: Elevation lower limit (deg)
Expected input: Real: 1 value
Specify the lower limit for acceptable elevations. All points
corresponding to lower elevations are rejected. The default flag-type is SHADOW.
Expected input: Character *24: 1 value
You may select one of the options at a time.
The logical ones, such as CORR/NOCORR will take effect immediately. For the
others, you will be prompted for (a) new value(s). The values shown below as
defaults are the ones with which NFLAG starts up.
Redefinition of the primary data cube:
HYPER: Change the primary data cube by selecting new polarisation,
interferometer and hour-angle ranges.
SECTORS: As HYPER but including a change of the SCN_SECTORS selection.
NODE: Completely new primary data cube (i.e. including new .SCN
file)
Data-correction modes. Shown in parentheses is NFLAG's initial setting:
CORR/NOCORR (=NOCORR):
Reading mode for visibility data: without/with corrections
applied and ignoring/acknowledging flags.
(NOCORR mode will be ignored in those cases for which the use
of uncorrected data would be pointless, e.g. ARESID, RRESID).
UFLAG (=ALL):
Default flag types to be acknowledged when reading data in
CORR mode.
Run modes:
SHOW/NOSHOW (=SHOW):
After each flagging operation, show/don't show a summary of the
new flag settings for the data cube and flag types selected
for
that operation.
Note that in either mode the affected flags will be counted
anyway, so you can use INSPECT afterwards to show summatries
from various perspectives
DRYRUN/NODRYRUN (=DRYRUN):
For any operation that would change flags in the .SCN file,
do/don't do a 'trial run' first, - e.g. to get a feeling for
sensible default values for clip limits etc.
(For NODRYRUN safe default values will be chosen for such
limits so that nothing will happen until the user sets his own
values.)
NOTRACE/TRACE (=NOTRACE):
Dont't/do trace the flagging operations through messages on the
terminal. TRACE is likely to produce a lot of output and
intended for debugging purposes only.
Navigation:
QUIT: Go back to FLAG_OPTION.
Prompt: Type of flagging operation|
Expected input: Character *24: 1 value
Specify the type of flagging operation to be performed:
Selective flagging on the basis of data/coordinate/statistics values:
CLIPDATA Flag data points according to a data-derived criterion
(amplitudes, selfcal residuals, etc.)
DETERM Flag data points on the basis of their coordinates (position,
elevation, etc.)
Deterministic clearing, setting and copying of flags:
CLEAR Clear flags from scan headers and data (see also MANUAL)
MANUAL Manual flagging operations (includes CLEAR flags).
HASCANS Operations on the scan-header flags. These affect ENTIRE
scans, and in doing so IGNORE the interferometers (parameter
IFRS) and polarisations (parameter SELECT_XYX) selections
that you defined for your primary/secondary data cubes.
FCOPY Copy flags from one place in the hypercube to another.
Operation on the flag list in core:
FLIST Operations on the internal flag list
(including reading-from/writing-to a .FLF file).
Define operating environment:
MODE Go to FLAG_MODE parameter to change 'environment' parameter
values. This includes re-definition of the primary data
cube.
Navigation:
INSPECT Go to the flag-INSPECTion group of operations.
STATIST Go to the data-STATISTICS group of operations.
QUIT Return to primary OPTION.
Prompt: hour angle range to process (deg)
Expected input: Real: 1 to 2 values
Specify the start and end of the HA-range to be processed. If
only one value is given, the end value will be the same.
Prompt: Input .FLF file name (including extension)
Expected input: Character *80: 1 value
Specify the full name of the input binary-flags file. The
recommended filename extension is .FLF.
Prompt: Flagging threshold
Expected input: Real: 1 value
Specify the limit threshold value for the (un)flag criterion
selected. The units (e.g. W.U.) are those appropriate for the criterion.
Prompt: flagging limits
Expected input: Real: 1 to 2 values
Specify the LOWER and UPPER limiting values for the (un-)flag
criterion. The unit (e.g. W.U.) depends on the criterion under consideration.
Prompt: elect data-thresholding criterion |
Expected input: Character *24: 1 value
Remember that only the primary data cube is affected.
The following operations flag individual data points, according to a flagging criterion that is derived from the visibilities themselves. You will be prompted for an upper limit. For each visibility point exceeding the limit the flag will be set if it exceeds the limit, for the others it will be cleared: Current flags are NOT preserved.
The flag type is CLIP, unless you have defined your own type through the USER_FLAGS parameter.
Flagging on straight data values exceeding the threshold. These criteria are intended for use with CORRECTED data (Parameter FLAG_MODE=CORR).
AMPL Threshold applies to absolute value
COS Threshold applies to real (cosine) part.
SIN Threshold applies to imaginary (sine) part.
Flagging on Selfcal/Redundancy residuals. You will be prompted to specify
the
Selfcal source model used in the latest NCALIB SEFCAL/REDUN run.
(NOTE that the residuals here are VECTOR differences between observation
and source model; this definition is different from that used by NPLOT.)
ARESID Threshold applies to the magnitude of the residual
RRESID Threshold is the absolute difference of the residual's
magnitude
from the average magnitude of all residuals in the scan for
the
same baseline. (In short: This flags outliers in sets of
redundant baselines.)
NOTE: This operation can be performed even on uncalibrated
data,
provided a source model is available.
Flagging on polarisation-related criteria:
QXY Threshold applies to the magnitude of the difference between XX
and YY visibilities per interferometer (i.e. magnitude of
Stokes Q for parallel dipoles).
UXY Threshold applies to ABS(XY-YX) per interferometer
(i.e. ABS(U) if the dipoles are parallel).
VXY Threshold applies to ABS(j(XY+YX)) per interferometer
(i.e. ABS(V) if the dipoles are parallel).
For unpolarised sources, this criterion should be as effective
as ARESID above.
Flagging on discontinuities in time. The flags raised here serve only as an ALERT that there is a 'jump' in the data; you will have to decide yourself what to do about the problem.
DT1 Threshold is the difference in amplitude of a data point with
its counterpart in the preceding scan.
Navigation:
INSPECT Make detour into the (flag) INSPECTion section of the program
STATIST Make detour into the (data) STATISTics section of the program
MODE Make detour into the environment MODE-control section of the
program
CLEAR Go to the CLEAR-flags operation.
QUIT Return to FLAG_OPTION.
Prompt: Select coordinate criterion |
Expected input: Character *24: 1 value
Remember that only the primary data cube is affected.
Flagging of data points on the basis of their coordinates. The flag type is SHADOW, unless you have selected your own type (parameter FLAG_MODE).
SHAD In each scan, flag all data that are affected by 'shadowing',
i.e. all interferometers in which the aperture of either
telecope is partly blocked by another telescope in the line
of sight.
PBAS Flag all data for which the length of the projected baseline
is within a range (for which you will be prompted). This is
a
way to eliminate short baselines susceptible to
interference,
without losing more data than necessary.
ELEVATION Flag all uv-data that have been taken at elevations below a
limit (for which you will be prompted).
REDUN Flag all redundant baselines.
NONRED Flag all non-redundant baselines.
Navigation:
INSPECT Make detour into the (flag) INSPECTion section of the program
STATIST Make detour into the (data) STATISTics section of the program
MODE Make detour into the enviornment MODE-control section of the
program
CLEAR Go to the CLEAR-flags operation.
QUIT Return to FLAG_OPTION.
Prompt: Flag-copy operation
Expected input: Character *24: 1 value
FCOPY propagates flags of the selected type from individual
interferometers to groups of interferometers that have something in common with
the flagged ones.
Flags are looked for in the entire primary data cube, but changes affect only the primary/secondary cube. Make sure that you understand which of the 8 flag types are affected
Operations that modify flags on individual data points:
TOTEL Copy flags from interferometers to telescopes: For each scan
selected, flag all data that share a dipole (X or Y channel of
a telescope) with any interferometer for which the flag
selected is set.
TOPOL Copy flags to all polarisations: For each scan selected, flag
all
polarisations of all telescope pairs for which the flag
selected
is already set for at least one of them. (This is a sort of
mini-PUT).
Operations that affect ENTIRE scans. NOTE that these IGNORE ANY SELECTIONS you have defined for interferometers (parameter IFRS) and/or polarisations (parameter SELECT_XYX).see the dictinction between data and header flags
TOHEAD For each flag selected, set the scan-header flag if it is set
for more than a given number (paremeter TOH_LIMIT) of data
points.
This invalidates the entire scan. The operation is reversible
(parameter OPS_MANUAL = CLHEAD); the individual data flags
are not affected.
See parameters TOH_LIMIT,
OPS_MANUAL
TODATA Transfer flags of the type selected from the header of each
scan
to all the scan's data, deleting them in the headers.
Navigation:
INSPECT Make detour into the (flag) INSPECTion section of the program
STATIST Make detour into the (data) STATISTics section of the program
MODE Make detour into the enviornment MODE-control section of the
program
CLEAR Go to the CLEAR-flags operation.
QUIT Return to FLAG_OPTION.
Prompt: Flag-list operation|
Expected input: Character *24: 1 value
Specify operations on the internal flag list: The entries in
this list represent flagging instructions. Each entry contains a flag type, and
ranges for the secondary data cube (i.e. hour angle, polarisation,
interferometer and channel ranges) to which it applies.
Flagging operations involving the internal flag list:
DELETE Clear the entire list.
GET Collect flags of specified type(s) from the specified primary
data cube, translate them into flaqg-list entries and merge
them into the list.
The default flag type is ALL, but it can be changed (parameter
FLAG_MODE).
see paremeter FLAG_MODE
PUT Use he entries in the internal flag list to set flags for
selected visibilities or scans.
If an entry in the list results in setting the flags on all
data
points in a scan, the corresponding scan-header flag is set
instead for efficiency reasons.
Transfer of the flag list to/from an external file. Two types of file may be used:
The .FLF file is in a compact binary format that is efficient in both
operating speed and disk-space. It is accessed through:
LOAD Merge contents of a .FLF file into the internal flag list
UNLOAD Write the internal flag list to a new .FLF file
The list can also be stored in an ASCII file which you can inspect and
edit
as you please. ASCII files are bulky and take much more time to process.
They are accessed through:
READ Merge contents of an ASCII flag-list file into the internal
flag
list
WRITE Write the internal flag list to a new ASCII flag-list file
Inspection:
HEADER Show the contents of the flag-list header.
LIST Show the contents of the flag-list (can be long).
LCOUNT Count the flags in the flag list (NOT in the data).
These can be INSPECTed in various one-dimensional projections.
Navigation:
INSPECT Make detour into the (flag) INSPECTion section of the program
STATIST Make detour into the (data) STATISTics section of the program
MODE Make detour into the environment MODE-control section of the
program
CLEAR Go to the CLEAR-flags operation.
QUIT Go back to what you were doing before.
Prompt: "-
Expected input: Character *24: 1 value
Count and inspect flags in the primary data cube. A complete reply consists of one of the primary options plus a modifier suffix.
Count flags (no modifier):
COUNT Count the flags of all types that are set, for subsequent
inspection.
You may define a secondary data cube for this operation
By default, flags of all types are counted; you may change this
(parameter FLAG_MODE).
Show the flag counts in various data-cube dimensions (<mod> stands for one of the optional modifiers listed below):
FTYP_<mod> Show the counts per flag-type (data and headers).
TEL_<mod> Show the counts per telescope.
IFR_<mod> Show the counts per interferometer.
HA_<mod> Show the counts per hour-angle (total over all
interferometers and polarisations).
Modifiers: You may limit the display of counts to a sub-set through one of
the following modifiers (prefixed with an underscore, e.g. TEL_SHAD, or
HA_XX). The display will be equivalent to that for a secondary cube
covering the same selection.
X, Y XX alone, YY alone
XY, YX only XX and YY, only XY and YX
MAN, CLIP, NOIS, ADD, SHAD, U3, U2, U1, OLD
for one flag type
<interferometer designation>
for a (group of) interferometer(s), e.g. FTYP_9A, HA_8*
<telescope>
for a (group of) telescope(s), e.g. FTYP_8
Navigation:
STATIST Make detour into the (data) STATISTics section of the program
MODE Make detour into the enviornment MODE-control section of the
program
QUIT Back out from INSPECT: Return to what you were doing before.
Prompt: Manual-flagging operation|
Expected input: Character *24: 1 value
Specify one of the manual flagging operations. Remember that
only the selected primary/secondary data cube is affected. Make sure that you
understand which of the 8 flag types are affected.
Clear flags. You will be prompted for the flag-type(s) to be cleared: BEWARE! Much work can be undone with careless clearing
CLEAR Clear all flags of the specified type(s) in both the
scan headers and the uv data of the selected cube.
CLDAT Clear flags on the visibilities only (i.e. leave scan headers
alone).
CLHEAD Clear flags in the scan headers only.
Set flags:
UVDATA Set flags of the specified type(s) in the individual
visibilities, for selected interferometer(s) within the
primary
data cube.
Default flag type is MANUAL, but can be overridden (parameter
FLAG_MODE).
HARANGE Set flags of the specified type(s) on the individual
visibilities, for selected interferometer(s) within the
primary
data cube.
Default flag type is MANUAL, but can be overridden (parameter
FLAG_MODE).
You will be repeatedly prompted for an hour-angle range.
Navigation:
INSPECT Make detour into the (flag) INSPECTion section of the program
STATIST Make detour into the (data) STATISTics section of the program
MODE Make detour into the enviornment MODE-control section of the
program
CLEAR Go to the CLEAR-flags operation.
QUIT Return to FLAG_OPTION prompt.
Prompt: elect scan-statistics flagging criterion |
Expected input: Character *24: 1 value
The operations available here flag scan headers and thereby
affect ENTIRE scans; in doing so they IGNORE ANY SELECTIONS you have defined
for interferometers (parameter IFRS) and/or polarisations (parameter
SELECT_XYX). Apart from this, only those scans that overlap with the primary
data cube are affected.
For each of the options an appropriate flag is selected, as noted below. If you have defined your own selection through the USER_FLAGS parameter, that selection will override NFLAG's defaults.see FLAG_MODE
see the dictinction between data and header flags
Flagging the scans that you select.
SCANS Flag scans manually; you will be given the option to select a
secondary data cube for this operation.
Flagging on data statistics. The default flag type is CLIP.
MAXABCS Flag all scans in which the modulus of either the real (cosine)
or imaginary (sine) part of any visibility falls outside a
range to be specified.
Flagging on noise statistics. The default flag type is NOISE.
ANOISE Flag all scans in which any of the four noise values (X/Y
gain/phase) recorded in the latest NCALIB ALIGN or SELFCAL
operation exceeds a threshold (yet to be prompted for).
XAN,YAN As ANOISE, but checking only the X resp. Y noise values.
RNOISE Flag all scans in which any of the four noise values (X/Y
gain/phase) recorded in the latest NCALIB REDUN operation
exceeds a threshold (yet to be prompted for).
XRN,YRN As RNOISE, but checking only the X resp. Y noise values.
Navigation:
INSPECT Make detour into the (flag) INSPECTion section of the program
STATIST Make detour into the (data) STATISTics section of the program
MODE Make detour into the enviornment MODE-control section of the
program
CLEAR Go to the CLEAR-flags operation.
QUIT Return to FLAG_OPTION.
Expected input: Character *24: 1 value
Accumulate statistics from data and/or scan headers over the
primary or secondary data cube and display it.
Accumulate:
ACC Accumulate statistics from data and scan headers, excluding
data
points/headers that are flagged.
You may select a secondary data cube for this purpose
(parameter
XXX).
Inspect the results of accumulation:
SCANS Show the collected scan-header statistics.
UVDAT Show the collected visibility statistics.
<name> Show the statistics of the named 'accumulation group' (use
GROUPS and EXPLAIN above to see what choices you have).
These options will produce a Table with the following columns:
<name> The name of the quantity for which statistics have been
calculated.
mean Its average value
rms Its rms magnitude
rmsms Its rms deviation w.r.t. the mean.
rmsvar The rms difference, between pairs of successively processed
values.
wtot Total weight. Usually it indicates the total nr of samples.
minval Its minimum value.
maxval Its maximum value.
<unit> The units in which the above values (except wtot) are
expressed.
Get some extra help:
GROUPS Show the names of the currently defined 'accumulation groups'
EXPLAIN Show explanation of statistical quantities.
Navigation:
INSPECT Make detour into the (flag) INSPECTion section of the program
MODE Make detour into the enviornment MODE-control section of the
program
QUIT Go back to what you were doing before.
Prompt: NFLAG main branch
Expected input: Character *24: 1 value
Specify the nature of the operation you want to perform:
FLAG: Set, clear and/or browse data flags in a .SCN file
and/or browse its data statistics
SHOW: Show/edit data and header information in .SCN file. This
option
is a clone of the SHOW option in NSCAN and is available here
for convenience.
QUIT: Terminate NFLAG
Prompt: Output .FLF file name (including extension)
Expected input: Character *80: 1 value
Specify the full name for the output binary-flags file. The
recommended filename extension is .FLF.
Prompt: Projected-baseline range to be flagged (m)
Expected input: Real: 1 to 2 values
Specify the range of lengths of PROJECTED baseline to be
flagged. The default flag-type is SHADOW.
Short baselines are more sensitive to interference. In flagging them wholesale, however, one also loses visibility data representing extended source structure; a more selective procedure is to be preferred.
Another application of this parameter is to force a uv coverage that is more nearly circular in the PROJECTED uv plane, and hence produces a more circularly symmetric antenna pattern. To this end, set the lower limit less than or equal to
<longest baseline> * sin DEC
Instead of permanently modifying the .SCN file in this way, one may use the NMAP parameters CWEIGHT_TYPE and CWEIGHT_VALUE to achieve a similar effect.see NMAP public paremeter CWEIGHT_TYPE
Examples:
PBAS_LIMITS = 0, 288
causes all projected baselines up to 288 m (inclusive) to be flagged.
For a source at a declination of 30 deg,
PBAS_LIMITS = 1500, 10000
will flag projected baselines longer than 1500 m.
Prompt: PUT expansion half-width in channel numbers
Expected input: Integer: 1 value
PUT performs flagging commands from the internal flag list on
your primary data cube. Each command consists of a flag/unflag mask plus ranges
in the frequency-
channel, interferometer, polarisation and hour-angle 'dimensions' of the TARGET
points to which it must be applied.
You have activated PUT's option to EXPAND, within the limits of the primary
data cube, the operation over a 4-dimensional volume of data around each target
point. You may now select the number of channels on either side of a target
channel over which you want to expand the flagging. Example:
If you reply 2, a total of 5 channels centered on each target channel
will be flagged: two above and two below the target.
Expected input: Character *8: 1 to 4 values
PUT performs flagging commands from the internal flag list on
your primary data cube. Each command consists of a flag/unflag mask plus ranges
in the frequency-
channel, interferometer, polarisation and hour-angle 'dimensions' of the TARGET
points to which it must be applied.
PUT has the capability to EXPAND, within the limits of the primary data cube, the operation over a 4-dimensional volume of data around each target point. The extension volume is specified through RANGES along the channel, hour-angle, interferometer and polarisation axes in this order. Except for interferometers, a range is formulated in terms of units of sequential position rather than physical coordinates. It can be one of the foloowing:
. do not extend along this axis
* extend to all positions along this axis
<n> or <n>C extend over <n>/2-1 positions on either side (incrementing <n>
if it is even)
<n>L extend over <n>-1 positions to the 'left' (i.e. toward lower
coordinates)
<n>R extend over <n>-1 fields to the 'right' (i.e. toward higher
coordinates)
The following special notations can also be used in each dimension:
<n>=0 suppress flagging altogether (length of the nextension cube is
zero)
<n>=1 identical to . (length of extension cube is 1: no extension)
The following shorthand can be used for the entire reply:
* short for 1,1,1,1 or .,.,., (You may do better to avoid this
form because this use of a wildcard character is anomalous.)
? The interferometer range works on telescope basis, i.e. the given range is ? valid for both receptors (e.g. 0Y and AX).
Example:
If a particular ineterferometer is flagged in one of frequency
channels,
PUT_RANGE= *,.,.,.
will propagate the flag to all channels for that interferometer
Prompt: Flag type(s) to use in data selection|
Expected input: Character *16: 1 to 16 values
Some operations test flags in selecting data. By default, NFLAG
selects the test flags appropriate to each operation; only those data are
accepted for which these flags are CLEAR.
You may define here an alternative (set of) flag type(s) to be used in ALL subsequent testing operations; you may select more than one, separated by commas. Reply NONE to revert to the default settings.
ALL or * test all flag types MAN test the flag type for the MANUAL class of operations CLIP test the flag type for the CLIP class of operations NOISE test the flag type for the NOISE class of operations ADD test the flag type for the ADDITIVE class of operations SHAD test the flag type for the SHADOW class of operations U1, U2, U3 'user' flag types, i.e. types you may use as you please NONE revert to NFLAG's default types per operation
OLD the flag type for the 'OLD' class (i.e. flagged before
930609, and converted with NVS option)
NB: OLD uses the same flag-bit as MAN
Prompt: Telescope shadowing diameter (metres)
Expected input: Real: 1 value
Specify the diameter (m) of the telescopes.
A telescope is 'shadowed' as soon as part of its aperture gets blocked by the presence of another telecope in its line of sight. This condition occurs when the projected baseline between the two telecopes becomes less than the telescope diameter D (25 m for the WSRT). If you want to retain as much as possible of your data, you may specify a somewhat smaller number (e.g. 0.8 D) to take into account the fact that the edge of the aperture is only weakly illuminated.
For the hour-angles at which a telescope is shadowed, all intreferometers are flagged of which it is a part. The default flag-type is SHADOW.
? Another flag may be selected through the FLAG_MODE parameter.
Prompt: Type of secondary data cube
Expected input: Character *24: 1 value
You may define a 'secondary cube' that includes only part of the
primary data cube. The current flagging operation will affect only the cross
section of the primary and secondary cubes.
Unlike the primary cube (which can only be redefined through the FLAG_MODE parameter), the secondary cube definition applies only to the current operation and will evaporate when it completes.
Specify here how you want to define the secondary cube. You may give ONE option at a time; the prompt will reappear until you reply with NO.
YES Polarisations, interferometers and hour-angle range.
IFR Interferometers
POL Polarisations
HA Hour-angle range
NO Accept the current settings
Prompt: Maximum number of data flags to tolerate per scan
Expected input: Integer: 1 value
NFLAG will check in each scan the number of points for which the
flag type selected is set. If that number exceeds this value you define here,
the entire scan will be flagged. This will subsequently result in faster
processing
(because individualdata points need not be tested) at the expense of the loss
of some healthy data.
The operation of setting header flags is reversible: The individual data flags are retained so you can restore the present condition by clearing the header flags.
Prompt: default flag type(s)
Expected input: Character *16: 1 to 16 values
Specify the default flag type(s) for flagging operations.
NONE: no flag type specified (i.e. use default types)
ALL or * all flag types (not very useful)
MAN flag type for the MANUAL class of operations
CLIP flag type for the CLIP class of operations
NOISE flag type for the NOISE class of operations
ADD flag type for the ADDITIVE class of operations
SHAD flag type for the SHADOW class of operations
U1, U2, U3 'user' flag types, i.e. types you may use as you please
Note: Flags U1, U2, U3 can be used to experiment with some flagging operation
without affecting the flag type that is 'officially' associated
with the same operation.
OLD use the flag type for the 'OLD' class (i.e. flagged before
930609, and converted with NVS option)
NB: OLD uses the same flag-bit as MAN
Prompt: Select flag type(s) for ALL flagging operations|
Expected input: Character *16: 1 to 16 values
Each flagging operation changes a specific flag type by default.
You may define here an alternative (set of) flag type(s) to be used in ALL
subsequent flagging operations. Reply NONE to revert to the default settings.
The purpose is to allow you to do experimental flagging with one of the USER flags without messing up the flagging that you have already done.
OLD use the flag type for the 'OLD' class (i.e. flagged before
930609, and converted with NVS option)
NB: OLD uses the same flag-bit as MAN
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.