Provided by: ncview_2.1.6+ds-1build1_amd64 bug


       ncview - graphically display netCDF files under X windows


       ncview  [-beep]  [-copying]  [-frames]  [-warranty]  [-private] [-ncolors XX] [-extrainfo]
       [-mtitle "title"] [-minmax fast | med | slow | all] datafiles ...


       Ncview displays 2-D slices of a netCDF data file, using the X Window System graphical user
       interface  (Release  4  or higher).  You can examine different floating point variables in
       the file, and animate the floating point data  along  the  ``record  dimension''  (usually
       time)  to  see  how  it  evolves.   You can also display 1-D (line plot) views of the data
       simply by clicking the mouse on the point of interest.

       When you first invoke ncview, a command panel comes up which has a number of  buttons  for
       manipulating the current view into the data file, and presenting various information about
       the current view.  From the top, going down, the information fields are:  the  'title'  of
       the data file; the 'long_name' of the currently selected variable; the frame number (i.e.,
       place along the scan axis) currently displayed; the minimum  and  maximum  values  of  the
       variable;  and  the value of the data point under the cursor (only active when the pointer
       is over the color contour image).

       Next comes a row of buttons similar to a tape recorder, used for changing  the  view  into
       the  netCDF  file along the scan dimension.  In Version 1.XX of ncview, the scan dimension
       is constrained to be the ``record dimension'' (in netCDF parlance).  From  the  left,  the
       buttons  are:  the  quit  button; a button to take you directly to the first frame, marked
       "->1"; rewind, which loops  the  images  going  backwards;  step  backwards;  pause;  step
       forwards; and fast forward, which loops the images going forwards.

       Below  this  is  the  row of option buttons, which from the left are: the colormap button,
       labeled with the name of the current colormap (see below);  "Inv  P",  which  inverts  the
       physical  representation  of  the  data (flips it upside-down); "Inv C", which inverts the
       colors currently being used  so  that  the  colors  indicating  minimum  and  maximum  are
       switched;  the  magnification  button,  which  sets  how  much  image  expansion the image
       undergoes; and the transformation button, which determines  what  preprocessing  the  data
       undergoes  before  display.  For this button, "Linear" means no preprocessing, "Low" means
       that the data is raised to the fourth power before conversion to  a  pixel,  so  that  low
       values  are  emphasized;  and  "Hi" means that the fourth root of the data is taken before
       conversion, so that large values are emphasized.  Next comes "Set Dim"; pressing this pops
       up  a  window which allows you to determine which variables are shown on the X and Y axes.
       Note that Version 1.XX of ncview will not transpose  your  data!   This  means  that,  for
       example,  you  cannot  simultaneously  display  the  X  dimension  along  the Y axis while
       displaying the Y dimension along the X axis---that would be an attempt  to  transpose  the
       data.   You  can  display  the  X  dimension along the Y axis if some other variable which
       varies less rapidly in your particular data file (for example, depth) is on  the  X  axis.
       Such a configuration is possible because it involves no transposition of data.  In general
       you don't have to worry about this issue much, because if you attempt to pick  axes  which
       would be transposing the data, ncview switches them (and tells you that it's doing so!) so
       you can get the axes you want.  Note  that  there  is  never  any  ambiguity  about  which
       dimensions  are being displayed on what axes; that information is always shown in the main
       panel.  Next is "range", which pops up dialog boxes to set the data min  and  maxes  which
       will  be contoured.  Pressing with the RIGHTMOST mouse button on the "range" button resets
       the ranges to match the currently displayed slice;  this  is  a  VERY  useful  option,  so
       remember  it  and  make  use of it frequently!  The last button shows the method currently
       employed for expanding the data onto the screen; the default, "bi-lin",  performes  a  bi-
       linear interpolation.  Also available is "repl", which simply replicates the pixels and is
       somewhat faster.

       The next row of buttons shows what variables can be displayed from the input files.   Note
       that  when ncview first comes up, if there is more than one variable in the file, you must
       select a variable to display before you will see anything.  If there is only one  variable
       in the file, the selection defaults to that one.

       Below  the  variable  selection  buttons  are  the  dimension information fields.  All the
       dimensions for the displayed variable which can take on more  than  one  value  are  shown
       here,  one variable to a line.  In each line, there are 6 fields of information; from left
       to right, they are: "Dim", the Dimension identifier, which is `Scan' if the  dimension  is
       currently  the scanned dimension (i.e., the dimension accessed via the tape-recorder style
       buttons), `X' if the dimension appears in the color contour display along the x  axis,  or
       `Y'  if  it appears in the color display along the y axis.  This field will be blank if it
       isn't Scan, X, or Y.  Next come "Name", the dimension's short  name;  "Min",  the  minimum
       value  of the dimension; "Current", the current value of the dimension as displayed in the
       color contour panel;  "Max",  the  maximum  value  of  the  dimension;  and  "Units",  the
       dimension's  units.   Clicking  on the "Current" field of a dimension allows you to change
       the current value of that dimension.  Clicking with the left mouse  button  increases  the
       current value of that dimension; clicking with the right button decreases it.


       You can get a popup X-Y (line) graph of data at a point simply by clicking on the point of
       interest.  You have several options at this point; with the bottons at the bottom  of  the
       window  you  can  change the axis along which the data is graphed (if there are other axes
       available), use log scaling for the X and/or Y axis, and set the data range.  You can also
       dump  out  the  data  from the X-Y plot into an text file, for easy importation into other

       Up to five line plots can be on one graph.  The panel on which the  next  line  plot  will
       appear  is  called  the "locked" panel.  If you don't want the next line plot to appear on
       the locked panel, then unlock it by pressing the "Locked" button.  At the  moment,  panels
       are automatically unlocked when you choose a new variable.


       ncview  supports time axes that use the conventions in the udunits package.  Typical units
       names in this scheme would be "days  since  1990-01-01".   If  ncview  encounters  a  time
       dimension  that  it  understands  in  this  way,  then  it  displays the calendar date (as
       calculated by the udunits package, not ncview) rathar than the  actual  axis  value.   For
       instance,   it   might  display  "3_Jun_1995"  rather  than  "Day  2390".   To  have  this
       functionality, the udunits package must be able to find the "udunits.dat" file.  You  must
       set  the environmental variable UDUNITS_PATH to the location of this file for ncview to be
       able to find it.


       Clicking on a button with the left mouse button  invokes  the  standard  action  described
       above;  clicking  with  the  right  mouse  button  on the colormap select, transformation,
       magnification,  or  dimension  "Current"  buttons  DECREASES  the  selection  instead   of
       increasing  it  (i.e.,  cycles  in  the  reverse direction).  Holding down the control key
       "accelerates" actions; while clicking with the left mouse button will increase the rate at
       which  the  rewind, step backwards, step forwards, and fast forward keys will step through
       the data.  When holding down the control key while clicking on the  magnification  button,
       the magnification DOUBLES or HALVES instead of incrementing or decrementing by one.

       Ncview  attempts  to save the displayed images in main memory, with each frame being saved
       as it is calculated for the first time.  This speeds up looping replays of the same  data.
       If  there  is  not  enough  memory  to  store  all  the  required  frames  at the selected
       magnification, ncview will inform you and automatically stop trying to  do  so.   Changing
       the magnification will again force ncview to try and allocate a image buffer.

       Since  the scaled, interpolated pixel maps are stored, the following operations will flush
       the image buffer and require recalculating the images if they are performed: inverting the
       data;   inverting   the   color   map;  changing  the  magnification;  changing  the  data
       transformation (linear, lo, or hi); changing the dimension; changing the  range;  changing
       the  pixel  replication  scheme.   Changing colormaps does not require refilling the image

       You can invoke ncview with multiple netCDF filenames on the command line, and it will  try
       to  present  the  data in a logical way; i.e., if there are identically named variables in
       the data files, it will try to treat them as if they were all in one giant data file.   If
       there are different variables in different files, it will let you choose to display any of
       the available variables.  This is generally a Good Thing,  but  if  you  have  identically
       named  variables  in different files with different attributes, ncview will not know which
       attribute you want to use and most likely will crash.


       It is important to set the data range correctly; otherwise, the color contour  might  come
       out  all  red, or all blue, or otherwise not very interesting.  There are a number of ways
       to set or manipulate the range: 1) Click with the left mouse button on the "range" button.
       This  pops up a dialog window letting you specify the minimum and maximum values directly.
       2) Click with the right mouse button on the "range" button.   This  scales  the  displayed
       data to the currently shown frame.  3) Click with the left mouse button on a data point in
       the color-contour window; this will set the minimum scaling to the value of the data which
       you clicked on.  4) Click with the right mouse button on a data point in the color-contour
       window; this will set the maximum scaling to the value of the data which you clicked on.


       -beep: rings the terminal's bell when stepping forward through frames in  movie  mode  and
       the loop is restarted.

       -extrainfo:  Puts  up  extra  information in the color-contour window.  This is useful for
       photographing the computer screen to make slides or pictures of the data.

       -frames: This will make ncview dump out the frames it displays in a series  of  PPM-format
       files.  You can then make them into an mpeg movie if you so desire (using tools other than

       -mtitle: Puts the following argument (enclosed in quotes) up as the title  of  the  color-
       contour window.

       -ncolors:  Sets  the  number  of  colors  which will be displayed.  Defaults to 200.  Must
       currently be less than 256.

       -private: Forces use of a private colormap.  This will cut down on the number of  colormap
       entries used, but will turn the rest of the screen annoying colors.

       -minmax:  determines  how the calculation of minimum and maximum values is done.  If fast,
       then only the first, middle, and last time entries of each variable are examined.  If med,
       then  every  fifth  time entry is scanned for extrema.  If slow, then every tenth entry is
       used.  If all, then every time entry is examined for extrema.  Default is "fast".

       -copying: prints out the  terms  under  which  ncview  may  be  copied,  distributed,  and
       modified.   Ncview  is  covered  under  the  provisions of the Gnu General Public Liicense
       Version 1.

       -warranty: Ncview comes with no warranty; this option prints out  a  fuller  statement  to
       this effect.


       Ncview  looks  in directory /usr/share/ncview for system-wide colormap (.ncmap) files.  It
       also examines the user's environmental variable NCVIEWBASE for the  name  of  a  directory
       which  contains  additional  colormap  files.   If that is not defined, then colormaps are
       sought in the user's home directory, and in the directory which ncview was run from.

       Colormap files have 256 lines, each consisting of one r g b triplet, where r, g, and b are
       integers  in  the range of 0 to 255.  There should be only whitespace separating the r, g,
       and b values on each line.  Colormap files end with the  extension  ".ncmap".   If  Ncview
       does not find any colormaps, it will complain, and supply a simple default map.

       It  is  necessary to install the applications default file, "Ncview", in your $XAPPLRESDIR
       directory for the program to function properly.  If the screen appears out  of  alignment,
       make sure that this installation has been performed.

       The  application  resources  file  recognizes  the following resources, in addition to the
       standard ones:

              The width, in pixels, of the information labels at the top of the main window.   If
              you  generally  use  long titles and variable longnames, you might want to increase
              this.  Default = 400.

              The width, in pixels, of the "variable" and "dimension" buttons.  If you  use  long
              names for these, you might want to increase this value.  Default = 50.

              The  number  of  variable  buttons in a row before a new one is started.  Set to be
              aesthetically pleasing to you.  Default = 5.

              The amount to step forward and backwards by when the control key is held down while
              pushing  the button.  If this value is less than 0, in indicates an absolute number
              of steps to take; if this value is greater than zero, it indicates the percent  (in
              integer  form,  from  1  to 100) of the total file size to step.  Default = 10 (ten


       Occasional bugs surface, especially when mixing variables in different files.

       Please send all bug reports to

                                              local                                     NCVIEW(1)