Appendix A : List of XAS environment variables

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• accummode

  This variable may be used to force accumulations to use non-default quantities on their X and Y axes ("pseudoaccumulations") or to revert to "normal" mode, in which the program uses the default x and y quantities.
  It may assume one of the following values :

  Normal Pseudo

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• ask

  This variable is by default OFF. In this case any error while processing the answer to a prompt in the XAS standard user interface will let the program continue or terminate, but will never re-ask for a correction.
  Setting ask to ON should be intended to enable re-asking.

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• askterminal

  This variable may be set to a single character, to change the "terminal escape" character (default !, an exclamation mark). The terminal escape character is used in XAS command files to force a request from the terminal.

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• axispen

  A standard XAS colour to be used for plotting axes.
  It defaults to the current pen value.

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• badtimes

  It may assume values Reject (default) or Correct, and indicates the action taken by the accumulation programs when encountering bad event times (the so called "spacecraft anomaly 80" for the Laben NFIs), if such events are ignored or recovered. Note that these events are fully recoverable. An isolated event will be always ignored anyhow.

  In the case of LECS bad event times are represented by the 64 s anomaly. All bad event times (including isolated ones) are corrected if such correction is requested (it is preferable to do so). Bad event times for the first or last event in a packet are alwyas unconditionally corrected.

  NB : LECS support is not part of the official distribution

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• bkgpen

  Reserved for a standard XAS colour to be used for the background of the plot window.
  

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• calfact

  This variable is a fractional number (0.0 to 1.0, current default 0.5 for MECS and 0.3 for LECS ) used by the gain history generation program to determine the range of channel in which the fit is performed. This range will be all channels around the peak which have a count level higher than calfact times the peak value.

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• caljump

  This variable is a number of channels (current default 3 for MECS and 12 for LECS ) used by the gain history generation program to determine the PHA range scanned by the fitting procedure : the procedure will step the peak position (and look for the minimum chi-square) in a range starting from caljump channels on the left of the data peak, for calstep steps of size calpass.

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• calpass

  This variable is the step (in fraction of a channel, current default 0.05 for MECS and 0.2 for LECS ) in the peak position used by the best fit procedure of the gain history generation program.

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• calstep

  This variable is the number of steps (current default 100) in the peak position used by the best fit procedure of the gain history generation program

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• caltype

  Reserved to set the default filetype extension for calibration files if not specified. Current default .calib (not used).

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• cmdstat

  It may assume the value PERManent to allow usage of a given command file with more that one program.

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• command

  This variable contains the current command file name (the type .command is assumed by default if not specified otherwise). The variable retains its value only for a single execution of the first called program (unless cmdstat is set to permanent).

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• context

  This variable specify the current default context for accumulation and display programs. Its main purpose is to default the type of accumulation and the filetype.
  Its value can be one of the following (the first letter is sufficient) :

  Image Spectrum Time Photon

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• correction

  This variable is used to enable accumulations to make instrument specific corrections.
  It may assume one of the following values :

  Disabled Enabled

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• countaxis

  This variable is used by the spectral and (HK) time profile accumulations to determine whether the data are expressed as count rates (cts/s, default) or raw counts..
  It may assume one of the following values :

  Rate Counts

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• countunits

  This variable is used when plotting a spectrum to choose whether the data are expressed as cts/s as they are in the file, or if the value is divided by the bin width (in channels, keV or other units). This is useful to compare data at different binning.
  It may assume one of the values Undivided (default) or Divided

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• datadir

  This variable points to the XAS pathname absolute (TBV) or (relative to rootdir) of the subdirectory where one wants to store data files, i.e. in case of SAX, the products of an accumulation (spectra, images, etc.), and all ancillary files (time windows etc.).
  In fact the actual directory name may be a subdirectory of datadir constructed from other environment variables ( target, date and instrument, according to current order.

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• datapen

  A standard XAS colour to be used for plotting data.
  It defaults to the current pen value (or cycles according to overcount in the case of overtraced plots)

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• datastyle

  This variable determines the "style" of plotting, to be choses among:
  • Solid all contiguous data points are connected by a solid line, which is broken only at gaps.
  • Histogram all contiguous data points are plotted as horizontal bars connected by vertical lines, with a "binned" appearance. The line is broken at gaps.
  • Errorbar all points are plotted with horizontal and vertical error bars. The size of the vertical error bar is the data error in the file, the size of the horizontal error bar is the binsize.
  • a diamond error mode is planned
  • a marker mode is planned
  In all cases the bin x-coordinate in the file is the start of the bin, while the reference point on the plot is the middle of the bin.

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• date

  This variable is used (optionally) to point to a subdirectory name, intended in the case one wishes to keep data separate by date. The full name of the directory is constructed from rootdir, a "data class" like datadir, fotdir or printdir, and optional date, target and instrument specification, and an user-selected order

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• echo

  This variable is by default ON. In this case the XAS standard user interface issues prompts to the terminal, and echoes the answer to prompts even when this comes from the runstring or a command file.
  Setting echo to OFF will disable prompts and echoes.

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• expolimit

  A fractional value (0.0-1.0, default 0.0) intended to be used to control rejection of time bins having an exposure fraction (deadtime column) lower than this value (default is to take everythign).

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• filespectra

  If this variable is set to YES the gain history generation program outputs also a file for each spectrum it is fitting. These spectra have sequential names of the form temp_nnn with a 3-digit sequence number.

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• fitplot

  Used internally by contributed front-ends to the spectral plotting program to discriminate a "best fit result" plot.

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• flight

  This variable is provisionally used to toggle between flight (FOT) data format and ground (calibration) data format for ground calibration purposes. It may assume the values ON|OFF (current default) or OFF (reserved for instrument team use).

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• fotdir

  This variable points to the XAS pathname absolute (TBV) or (relative to rootdir) of the subdirectory where one wants to store "telemetry" files, i.e. in case of SAX, the files coming from a FOT.

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• fotorder

  This variable is used to specify that the name of the FOT directory is built from rootdir, fotdir and eventually target, date, etc. bypassing the standard order. The value of this variable may be of the same form as those of order.

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• fourout

  Used by timing analysis programs (NB : timing programs are not part of the official distribution) to control the format of output files
  • Xas XAS binary table format
  • Asc XAS ASCII tabular format

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• freqaxis

  Used by the Fourier spectrum or periodogram plotting programs (NB : timing programs are not part of the official distribution) to plot data versus Frequency (default) or Period

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• gainhistory

  This variable is set to the name of a gain history file to be used by accumulation programs to perform any correction for the dependency of gain with time.

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• hkconvert

  This variable may be used to disable conversion of HK parameters to engineering units or to revert to the default conversion enabling.
  It may assume one of the following values (first letter is sufficient) :

  Enable Disable

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• hms

  If this variable is set to Yes the tlist program will display times as formatted hh:mm:ss.ff instead of the default raw format.

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• includegap

  It assumes the values Enabled (default) or Disabled and controls whether intervals with missing data (gaps) comprised between "good" time windows are included within the intensity window , or excluded causing separate time windows.

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• instrument

  This variable selects which of the SAX instruments is being processed, and directs accordingly the location of the calibration directory.
  It may also be used in conjunction with other environment variables to construct the path name for data storage according to current order.

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• lastbins

  Used only internally by the time profile plotting program to keep track of the bins plotted to allow faster scrolling (avoid reading useless data).

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• lastcomment

  Used internally by plotting programs to keep temporarily the status of plotcomment.

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• lastfit

  Used internally by contributed fitting programs and front-ends to the spectral plotting program to store the name of the last fitted spectrum.

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• lastplot

  Used internally by plotting programs to store the name of the last data file plotted in a fresh frame.

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• matform

  This variable selects the format of response matrix files
  It may assume one of the following values (first letter is sufficient) :

  Ogip Xas

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• mycaldir

  The path name of an alternate private directory where an user keeps private copies of calibration files. If set, such files will be used in preference to those in the standard calibration directory. If a file is not present in the private directory, the standard one is used anyhow.

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• nlevel

  Used to set the number of colour levels used by the image plotting program (default is 16, it shall be less or equal than the number of colours in the current colour table).

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• obschain

  This variable contains the current observation chain and is set exclusively via the concatenate command

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• observer

  This variable is used, if set, to generate an OBSERVER keyword in the file headers different from the default (which is the PI name read from a FOT tape directory). This variable may be set to :
  • any string (without imbedded blank) containing the wished name
  • OVERRRIDE to use your system login name

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• oldtimeref

  Used only internally by the time profile plotting program to keep track of the TIMEREF reference time (midnight) of the last plotted file, in order to allow overplotting of files with a different reference date.

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• order

  This variable is used to control the way directory names are assembled from rootdir, a "data class" like datadir, fotdir or printdir, and optional date, target and instrument specifications.
  It may assume a string value of one to four characters, to be chosen among the following, and given in the desired order :
  • * "don't care" placeholder
  • C data class
  • I instrument
  • T celestial target name
  • D observation date

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• overcount

  Set internally by plotting program to keep a count of how many data files have been plotted in the current frame. It is used to drive the cycling of colours for data overplotting (as such it may be altered willingly by a knowledgeable user).

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• overlay

  This can be Enabled (default) or Disabled. It is used by program skytopix to allow overplotting (on the displayed image) of a marker at the pixel position converted from a given RA and Dec.

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• overwrite

  A transient variable used internally by plotting program to handle overplotting.

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• pen

  A standard XAS colour to be used as default for all kind of plotting.
  

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• piccorr

  This variable is used to enable in LECS accumulations the LECS specific PI to PIC correction. It may assume one of the following values :

  Disabled Enabled

  NB : LECS support is not part of the official distribution

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• placeholder

  This variable may be set to a single character, to change the "placeholder" character (default ., a dot). The placeholder character is used in the standard XAS user interface to replace a runstring argument to be defaulted (asked to terminal). Two commas around a null or blank value are equivalent to a placeholder.

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• plotcomment

  This variables determines the extent of the annotations used on a plot (and indirectly the extent of the plotting region).
  It may assume one of the following values (first letter is sufficient) :

  Long Short None

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• plotter

  This variable is used to direct all plots to a given instance of a plotting server. If not set, it may default to a program-specified default, or fall back to the default xw1 server.

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• poweraxis

  Used by the Ferraz-Mello Fourier spectrum program (NB : timing programs are not part of the official distribution) to control the units for the power spectrum. It may assume the values Power (default, to plot power spectrum in arbitrary units) or Significance (to plot the Q chance probability) or Inverse (to plot the probability P=1-Q)

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• printdir

  This variable points to the XAS pathname absolute (TBV) or (relative to rootdir) of the subdirectory where XAS will put log files and other ancillary output files intended for printing or looking at.

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• printorder

  This variable is used to specify that the name of the print directory is built from rootdir, printdir and eventually target, date, etc. bypassing the standard order. The value of this variable may be of the same form as those of order.

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• quiet

  This variable is used to enable additional, moderately verbose, terminal output from several programs. It may assume one of the following values (first letter is sufficient) :

  Yes No

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• result

  This is never set explicitly but only as a result of the execution of some programs, and provides a generic way to pass back some (numeric) results for manipulation in procedures.

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• rootdir

  This variable points to the XAS pathname of the directory under which all XAS "logical directories" are rooted.

  If one wants to store all data (FOT data, reduced data etc.) under one's own common subdirectory (on the same filesystem) one can use notation
  

  xasset rootdir /mydir/mydir/...

  If one instead wants to use subdirectories on different file systems one MUST use notation
  

  xasset rootdir /

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• scroll

  This variable defines the time direction for the scrolling of time profiles. It may assume one of the following values (first letter is sufficient) :

  Forward Backward

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• scrollsize

  This variable has as value a real number in the range 0.0 to 1.0 and defines of what fraction of the current x-axis a time profile plot shall be scrolled.

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• selectfile

  This is either the name of a XAS image (map) or of a SAOImage-style region file to be used for spatial region selection, according to the setting of the selection method.

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• selectmethod

  This variable selects the method for the spatial region selection.
  It may assume one of the following values (first letter is sufficient) :

  Map Region

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• spacing

  Used by Fourier spectra programs (NB : timing programs are not part of the official distribution) to control whether frequency axis is divided
  • LIN into linear steps of given width
  • LOG into a given number of logarithmic steps

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• servers_xx

  This is never set explicitly but only when starting or registering a graphics server and contains the current list of registered servers of type xx.

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• slew

  This variable is used to select the part of the current observing period to be analysed (remember that observations are numbered 1 to n in EACH part), and may assume the values :
  • Normal for normal pointing data
  • Ingoing for the ingoing (initial) slew
  • Final for the outgoing (final) slew

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• spacecraft

  This variable is set to the current satellite mission and is used to access calibration data files and/or specific programs. It does not need to be set by the user, the first SAX specific program will set it to SAX.

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• target

  This variable is used (optionally) to point to a subdirectory name, intended in the case one wishes to keep data separate by celestial object. The full name of the directory is constructed from rootdir, a "data class" like datadir, fotdir or printdir, and optional target, date and instrument specification, and an user-selected order

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• temporary

  A transient variable used internally by plotting program to handle scrolling.

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• textpen

  A standard XAS colour to be used for plotting text.
  It defaults to the current pen value.

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• timeaxis

  This variable controls the annotation of the x-axis in plots, when the x quantity is time. The annotation may be in elapsed seconds from midnight, or in hours (hh:mm:ss).
  It may assume one of the following values (first letter is sufficient) :

  Seconds Hours

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• timeunits

  This is used by accumulation programs to determine the units used for time when outputting time profiles (times are always elapsed since the midnight of observation start).
  It may assume one of the following values :

  Second MILlisecond MICrosecond

  NOTE THAT ONLY USAGE OF "seconds" HAS BEEN TESTED.

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• timewindow

  This variable contains the name of the current time window file.
  Unset it (or set it to blank) to disable time windowing (as default).

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• tquantity

  This variable is used to select an alternate quantity to be plotted, when plotting time profiles. Simple time profiles contain only a scalar DATA column, and it is not necessary to do anything.
  In case of more complex time profile this variable may be used to select alternate columns as follows :
  • Deadtime to plot the deadtime column if present
  • Other to plot the "other data" column if present
  • n to plot the n-th element of a multidimensional DATA column

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• useimage

  This can be Enabled (default) or Disabled. It is used by programs dealing with attitude conversion from/to pixel coordinates to know whether basic attitude (and detector) information is derived from the last plotted image (if any), or is forced to be asked to the user.

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• verbose

  This variable is used to enable additional, extremely verbose, terminal output from sa few programs. It may assume one of the following values (first letter is sufficient) :

  No Yes

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• viewport

  This is a xasplot variable, whose values is a comma-separated list of four numbers in the range 0.0-1.0 :
  • the lower X coordinate of the plotting viewport in normalized coordinates (i.e. as a fraction of the plotting page)
  • the upper X coordinate of the plotting viewport
  • the lower Y coordinate of the plotting viewport
  • the upper Y coordinate of the plotting viewport

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• writeaux

  Used by timing analysis programs (NB : timing programs are not part of the official distribution) to control whether auxiliary information (useful for debugging) is written into the output files. It may assume values Disabled (default) or Enabled

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• XASTOP

  This is NOT a XAS environment variable, but a system environment variable which must be set to the top directory holding the XAS distribution tree. This setting shall be done (e.g. in a login file) before using any XAS command.

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• xaxis, yaxis

  These are xasplot variables, whose values is a comma-separated list of two numbers, corresponding to the extrema of the X or Y axis in the current world units.
  It may also assume the value AUTO (default) to let the program set the extrema automatically, or to NICE for a better (rounded) automatic choice.

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• xquantity

  This variable indicates the mnemonic name of the quantity to be used for accumulation on the x-axis (for images) or the only axis (for spectra).

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• xscale, yscale

  This variable determines whether the X or Y axis is linear or logarithmic. It may thererfore assume one of the following values :

  LIN LOG

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• xyaxis

  This is a xasplot variable, whose values is a comma-separated list of four numbers. It is used internally to keep track of the X- and y-axis extrema in the last plot.

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• xyunit

  This is used by program pixtosky to determine whether user supplied X Y coordinates are in Linearized pixels (default), Unlinearized pixels or directly in mm ( setting to Mm).

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• yaxis

  See xaxis.

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• yquantity

  This variable indicates the mnemonic name of the quantity to be used for accumulation on the y-axis (for images).

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• yscale

  See xscale.

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• zerogap

  It assumes the values Disabled (default) or Enabled and is intended to control whether time bins with zero value are considered as valid data (default) or shall be rejected as if they were gaps.

  ---

• zscale

  This variable is intended to give the user a choice of the way the "Z" scale is chosen when displaying an image. The foreseen values are :
  • Histogram equalization mode (only current form)
  • LInear scale
  • LOgarithmic scale
  • User selected scale
  • File : scale taken from an external file

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