U.S. GEOLOGICAL SURVEY OPEN FILE REPORT 94-255

       The Southern Lake Michigan Coastal Erosion Study CD-ROM


      By  C.F. Polloni1, C.L. Brown2, D.W. Folger1, D.S. Foster1,
                           and A.L. Brill3


                 Display software by Russell A. Ambroziak4
                 Documentation by Christine A. Cook4



    1U.S. Geological Survey, Woods Hole, MA 02543
    2U.S. Forest Service, Jacksonville, OR 97530
    3Duke University, Durham, NC 27708
    4U.S. Geological Survey, Reston, VA 22092


                               IMVIS.DOC

       Program  'IMVIS'  is  a C language program that uses  a  graphics 
       library  developed by the USGS and is used to display  scientific 
       data.   If you have any questions concerning the program,  please 
       contact the creator:

                       Russell A. Ambroziak
                       U.S. Geological Survey
                       National Center, Stop 915
                       Reston, VA 22092

                       Tel: 703-648-6168
                       Fax: 703-648-5464



       IMVIS

       Program Description:

       Uses  a  label file to view an 8-bit image.   The full  image  is 
       displayed on the screen, in sampled mode if necessary, and allows 
       zooming, histograms, and lat/lon of pixels if label file contains 
       coefficients.

       How to Start Program:

            imvis

            Move the cursor to highlight the image you wish to select
            and press 'enter'.

       Files Needed to Run Program:

            *.lbl -- label file in following format:

            FILE_TYPE                       = IMAGE
            IMAGE_LINES                     =  1400
            LINE_SAMPLES                    =  1120
            IMAGE_POINTER                   = 'sta03.dat'
            PAL_POINTER                     = 'sta03.pal'
            SAMPLE_BITS                     = 8
            END


       Optional Files:

       Look up table or palette file if a color table is available.

       If no palette is given, a gray palette will be used.

       Output Files:

            *.tga -- a 32-bit targa file of the screen can be saved
        to a disk file.

       Related Programs:

            none

       Compile Command Line:

            cl /AL imvis.c vimage3 graphlib


what follows is the IMVIS tutorial from the GIV toolkit available on the
USGS ftp server in Reston; OEMG.ER.USGS.GOV   anonymous ftp, pub\GIV



               USGS-OEMG Image Visualization Software Tutorial

   
                    Software by Dr. Russell A. Ambroziak
                    Tutorial by Christine Cook

                    U.S. Geological Survey
                    Office of Energy and Marine Geology      
                    National Center, Mail Stop 915
                    Reston VA 22092

                         Tel : 703-648-6481
                         Fax : 703-648-5464









   * * * To view images contained within square brackets, hit the F6 key
   to highlight the image and then hit the <enter> key to view the image. 
   The images [canon02], [canon03], and [canon04] are quite dark; you may
   need to adjust the brightness on your monitor to see the image on the
   screen. * * *











                       * * * Table of Contents * * *


   Introduction.....................................................Page  1

   System Requirements..............................................Page  2

   Disclaimer.......................................................Page  2

   Descriptions of the Different Types of Label Files...............Page  3
        Example 1:  Simple Gray Scale Image.........................Page  4
        Example 2:  Color Image.....................................Page  5
        Example 3:  Registered Image set............................Page  6
        Example 4:  Composite image created by IMVIS................Page  7
        Example 5:  Earth Located Image -- Polynomial Fit to
                    Projection......................................Page  8
        Example 6:  Earth Located Image -- Albers Equal Area
                    Projection & MAPPER Data........................Page  9 
        Example 7:  Earth Located Image -- Mercator Projection
                    & MAPPER Data...................................Page 12
     
   To View a Single Image...........................................Page 14

   IMVIS Quick Reference Guide......................................Page 15
     
   Description of IMVIS Functions...................................Page 16

   To Create An 8-bit Color Image...................................Page 19

   Other Options for a Registered Set Label File....................Page 24

   To Digitize Linework.............................................Page 26






                          * * * Introduction * * *


        Program IMVIS, created by Dr. Russell Ambroziak of the U.S. Geo-
   logical Survey, is a simple to use image viewer which uses ASCII label
   files to describe the binary image data files.  Program IMVIS can also
   do some limited image processing such as converting three images out of
   a set of N images to either 24-bit or 8-bit color images with color
   palettes.  Some boxcar filter applications are possible, such as
   smoothing and relief shading, and color palette changes can be made in
   both IHS (Intensity, Hue, and Saturation) and RGB (Red, Green, Blue)
   space.

        Color images made from red, green and blue input files can be
   analyzed in 5-dimensions (x,y,R,G and B) with program MAKE5D.  Program
   EIGEN will N-dimensionally rotate up to 10 registered images and output
   a new image set of up to N images with a new set label.  These eigen
   vector images can then be viewed or processed via IMVIS in the same way
   as the original images. 






                       * * * System Requirements * * *


        IMVIS and it's related suite of image processing software, are
   programs written for the IBM PC and compatible microcomputers.  The 386
   models are recommended for speed, but the programs will work on the 286
   machines.  Other requirements :
    
             640 kb RAM
             MS- or PC-DOS* version 3.1 or later
             Microsoft MSCDEX version 2.1 or later
             hard disk drive with minimum 4 megs of free memory
             EGA/VGA graphics system with one of the following: 
                 TSENG 3000 or 4000 chip set (Orchid)
                           or
                 PARADISE VGA Professional Board
                           or
                 ATI VGA XL Wonderboard
                           or
                 TRIDENT Graphics card
              


   * Any use of trade, product, or firm names is for descriptive purposes
   only and does not imply endorsement by the U.S.  government.






                           * * * Disclaimer * * *

        Although this program has been used by the U.S. Geological Survey,
   no warranty, expressed or implied, is made by the USGS as to the
   accuracy and functioning of the program and related program material,
   nor shall the fact of distribution constitute any such warranty, and no
   responsibility is assumed by the USGS in connection therewith.






       * * * Descriptions of the Different Types of Label Files * * *


        The heart of the system is the label file which is patterned after
   the JPL 'IMDISP' ASCII label files.  For program IMVIS, each image must
   have it's own separate label file.  The simplest label file possible is
   a file of type '.lbl' containing the rows, columns and image data file
   name.  The following is an example of a simple .LBL file 'xxx.lbl':

        IMAGE_LINES        = 2057
        LINE_SAMPLES       = 1435
        IMAGE_POINTER      = 'l:\coredata\PD356001.dat'

        This will view file 'l:\coredata\PD356001.dat' which is a box of
   rock cores from the USGS 'Sampler of Digital Rock Core Information from
   the Core Research Center' CD-ROM.  It tells IMVIS that the image has
   2057 lines and each line contains 1435 pixels (picture elements).  The
   image is assumed to be a gray scale image with no color palette file. 
   Each pixel will be one byte in size and there is no header in the image
   file, which is in directory \coredata\ on CD-ROM drive L:.  If you copy
   'IMVIS.exe' to your hard disk, enter 'xxx.lbl' into a file on your hard
   disk, and enter the word IMVIS, then the following screen should
   appear: 
 

                                         *.lbl                         

Use up and down arrow keys, PgUp or   .OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO&
PgDn, or type the filename to positiontxxx      LBL      128  2/21/92 1102 t
highlighted cursor.  Hit 'Enter' to   /OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO'
select the file or 'Esc' to leave this
menu.                                   
                                                                       
    
     When a box appears on an image use:                               
   
     (l)arger or 
     (s)maller 

          to change size.

     If the shape of the box can be
changed use:

     (H)igher,
     (S)horter,
     (W)ider, or
     (N)arrower

          to change shape.



        If you have a CD-ROM reader installed as drive L: and have the
   Core Library disk in it, hit <enter> to display the image. It is not
   necessary to include path names in the label file as they can be
   entered on the command line :

        imvis d:\imgdata\land\ d:\imgdata\water\

   The above will cause the program to check d:\imgdata\land\ and 
   d:\imgdata\water\ as well as the current directory and the directory in
   which 'imvis.exe' is located when opening files or giving lists of
   label files.


   	In general the label files are a bit larger than the above
   example, and contain more information in them.  The following are six
   examples of '.lbl' files in order of increasing complexity.



   Example 1:  Simple Gray Scale Image

        FILE_TYPE          = IMAGE
        IMAGE_LINES        =  400
        LINE_SAMPLES       =  640
        HEADER_BYTES       =    0
        IMAGE_POINTER      = 'canon01.dat'
        END

        This is the simplest type of label file.  Three of the lines are
   not needed but are included for clarity : 

   	FILE_TYPE is not necessary but helps tell someone why this file is
   		here. 
   	HEADER_BYTES in this case is zero; the default.  These bytes are
   		skipped when the image is processed. 
   	END is not required by IMVIS, but other programs which can read
   		this type of file require it.  
   	IMAGE_LINES are the number rows in the image file.
   	LINE_SAMPLES are the number of columns in the image file.
   	IMAGE_POINTER is the name of the image file.




   Example 2:  Color Image

        FILE_TYPE          = IMAGE
        IMAGE_LINES        =  400
        LINE_SAMPLES       =  640
        HEADER_BYTES       =    0
        IMAGE_POINTER      = 'canon01.dat'
        PALETTE_POINTER    = 'canon01.pal'
        END

        This file is identical to the first except a palette file name has
   been given.  This is a list of red, green and blue values that define
   up to 256 colors.  The format is four integers on a line -- color
   number, red, green and blue.  All numbers range from 0 to 255.  An
   example of a typical palette file follows :

     #  R   G   B   <-- not in file, but given here to ID the columns
     -------------		
     0   8  15  11
     1  32  21  65
     2  40  22 107
     3  18  68  20
     4  36  70  65
     5  41  68 107
     .   .   .   .
     .   .   .   .
     .   .   .   .
   255   0 128   0




   Example 3:  Registered Image set

        FILE_TYPE          = IMAGE
        IMAGE_LINES        =  400
        LINE_SAMPLES       =  640
        SET_POINTER        =    6
          canon01.dat  40  70 100
          canon02.dat  10  30  50
          canon03.dat  10  37  65
          canon04.dat   5  37  70
          canon05.dat   0  65 130
          canon07.dat   0  33  65
        END

        If you have a set of images of the same scene, but with different
   information, (i.e. the seven different channels of Thematic Mapper
   data) they can be combined into an image set.  All images must be of
   the same size and each pixel must be of the same geographic location. 
   In short they must be registered.  Currently you can have up to 20
   images in a set.  This can be extended to any reasonable number by
   changing the macro NUM_IMAGE in the source code for 'IMVIS.C' and
   recompiling. 

   	"SET_POINTER = 6" in the above example means that there are 6
   images in the set.  The "END" is for the file, not the image set.  The
   names of the images are listed followed by optional scaling parameters.
   These indicate the image value to be plotted as 0, 127 and 255 in the
   output image.  If there are no numbers the default is 0, 127, and 255
   which means no change in the way the image is displayed.  If there are
   only two numbers they are assumed to be the first and last parameter
   and the middle is chosen to be their average. 




   Example 4:  Composite image created by IMVIS

        FILE_TYPE          = IMAGE
        IMAGE_LINES        =  400
        LINE_SAMPLES       =  640
        IMAGE_POINTER      = 'can_432.dat'
        PAL_POINTER        = 'can_432.pal'
        PALETTE_POINTER    = 'can_432.pal'
        SAMPLE_RATE = 1
        CHANNEL_INPUT:
           RED   = canonb4.dat Range =  11  40  65
           GREEN = canonb3.dat Range =  13  34  61
           BLUE  = canonb2.dat Range =  15  28  46


        This label file was created by IMVIS (see section describing IMVIS
   program functions) and is for a color composite image from channels 4,
   3 and 2.  The ranges indicate that for the red channel 0 on the screen
   is 11 (or less) in the file, 127 on the screen is from 40 in the file,
   and 255 on the screen is from 65 (or greater) in the file.  The sample
   rate is 1 which means that every pixel was used.  A sample rate of 2
   means every second pixel is used, etc.  The file names are given here
   so that IMVIS can read pixel data from them in 'pixel info' mode.




   Example 5:  Earth Located Image -- polynomial fit to projection

        FILE_TYPE                       = IMAGE
        IMAGE_LINES                     =  4583
        LINE_SAMPLES                    =  3132
        IMAGE_POINTER                   = 'pac36.glo'
        LATITUDE_COEF  = 6
         4.9993160e+001  -4.4824000e-004  -2.7323000e-011
         2.7988001e-005  -2.0332001e-009  -3.3854000e-010
        LONGITUDE_COEF = 6
        -1.2918469e+002   6.9518998e-004   4.0232001e-010
         4.3117001e-005  -4.0440001e-010  -6.1135998e-009
        END

        The addition of LATITUDE_COEF and LONGITUDE_COEF allow the program
   to convert X and Y in the image file to latitude and longitude.  This
   is useful when the projection of the map is unknown.  The upper left
   corner of the image is X=0 and Y=0 with X increasing to the right and Y
   increasing downward.  Because north is up on many images the order of
   the X and Y are reversed in the two equations :

   Lat = A(0) + A(1)*Y + A(2)*X + A(3)*Y*Y + A(4)*X*X + A(5)*Y*X
   Lon = B(0) + B(1)*X + B(2)*Y + B(3)*X*X + B(4)*Y*Y + B(5)*X*Y

        For the above example, the polynomial fit is :

   LAT=5.0 - 4.48e-004y - 2.732e-011x + 2.79e-005y*y - 2.03e-009x*x
               - 3.38e-010x*y
   LON=-1.29e+002 + 6.95e-004x + 4.02e-010y + 4.31e-005x*x - 4.04e-010y*y 
               - 6.13e-009x*y

        You can also get the x and y from the lat and lon via the 
   following equations :

   X = A(0) + A(1)*lon + A(2)*lon*lon + A(3)*lat + A(4)*lat*lat + 
               A(5)*lat*lon
   Y = B(0) + B(1)*lat + B(2)*lat*lat + B(3)*lon + B(4)*lon*lon + 
               B(5)*lat*lon

        This example uses 6 values for latitude and 6 for longitude but
   any number from 2 to 6 can be used as long as the order shown above is
   used.  If only 5 are used the last value is dropped, etc.




   Example 6:  Earth Located Image -- Albers Equal Area Projection &
               MAPPER Data
            
        FILE_TYPE          = IMAGE
        IMAGE_LINES        = 1575
        LINE_SAMPLES       = 2627
        IMAGE_POINTER      = 'rad_shd.dat'
        PAL_POINTER        = 'rad_shd.pal'
        PALETTE_POINTER    = 'rad_shd.pal'
        Projection = Albers equal area elliptical
            23.0  Lat0
            29.5  Lat1
            45.5  Lat2
           -96.0  Lon0
        -2630000  X0
         3328046  Y0
            2000  PixelSize (meters)
               7  ellipsoid (Clark 1866) (0-10)
        VECTOR_SETS = 6
          county = 1
             county 120.0 0.0 253
          coast  = 1
             coast  120.0 0.0 254
          state  = 1
             state  120.0 0.0 246
          rivers = 1
             rivers 120.0 0.0 251
          nation = 1
             nation 120.0 0.0 245

        The addition of Projection allows the program to convert X and Y
   in the image file to latitude and longitude and back again.  In the
   case of a projected image there are two sets of x/y coordinates -- one
   for the map and one for the image.  The image is in pixels as before
   but the map x/y is in meters from the map origin.  At this time only
   Albers equal area elliptical projections and Mercator projections can
   be processed but others will be added as the need arises.  The in-
   formation presented is as follows:

           Lat0 = central latitude of map
           Lat1 = 1st standard latitude
           Lat2 = 2nd standard latitude
           Lon0 = central longitude of map
             X0 = x map coordinate of pixel 0,0
             Y0 = y map coordinate of pixel 0,0
      PixelSize = map coordinate size of a pixel in meters
      ellipsoid = number of ellipsoid used in making map

           0  GRS 80        1980 6378137.0 6356752.3  Newly adopted
           1  WGS 72        1972 6378135.0 6356750.5  NASA, DoD, oil Co.
           2  Australian    1965 6378160.0 6356774.7  Australia
           3  Krasovsky     1940 6378245.0 6356863.0  Soviet Union
           4  International 1924 6378388.0 6356911.9  Remainder of the
   										 World
           5  Hayford       1924 6378388.0 6356911.9  Remainder of the
   										 World
           6  Clarke        1880 6378249.1 6356514.9  Most of Africa;
   										 France
           7  Clarke        1866 6378206.4 6356583.8  North America;
   										 Philippines
           8  Airy          1830 6377563.4 6356256.9  Great Britain
           9  Everest       1830 6377276.3 6356075.4  India;Burma;Pak;
   										 Afgan.;Thailand;etc.


        Line work from program mapper can be brought in by using the
   vector set option:

       VECTOR_SETS = 6            < there are 6 groups of lines     >
          county = 1              < group 1 'country' has 1 file to >
             county 120.0 0.0 253 < be plotted in color 253 for     >
                                  < pixel size 120 to 0 kilometers. >
          coast  = 1
             coast  120.0 0.0 254
          state  = 1
             state  120.0 0.0 246
          rivers = 1
             rivers 120.0 0.0 251
          nation = 1
             nation 120.0 0.0 245

        The colors may be any color in the image .PAL palette file by
   number.  If Program 'img8bit' was used (this is what is used if IMVIS
   makes the image, see 'To Create an 8-bit Color Image') the last 16
   colors will be as follows:

               
               number color name  R   G   B
                   
                 240  BUFF       105  90  75
                 241  BLACK        0   0   0
                 242  D_GRAY      70  70  70
                 243  M_GRAY     127 127 127
                 244  L_GRAY     191 191 191
                 245  WHITE      255 255 255
                 246  RED        255   0   0
                 247  ORANGE     255 128   0
                 248  YELLOW     191 192   0
                 249  GREEN        0 191   0
                 250  CYAN         0 191 191
                 251  BLUE         0   0 255
                 252  MAGENTA    191   0 191
                 253  BROWN       96  28  14
                 254  D_CYAN       0  91  91
                 255  D_GREEN      0 128   0


        The are differences between plotting vectors in IMVIS and in
   MAPPER.  These differences are as follows :

        1) For IMVIS, projection is important and you must tell the
   program the projection of the image.  Currently, only three types of
   projection can be handled.  These are : Mercator, Albers Equal Area,
   and a Polynomial-fit Projection.  In MAPPER, projection plays a very
   minor role.

        2) IMVIS does not require the vectors to be turned ON or OFF as
   MAPPER does.  This is because in IMVIS, none of the vectors will
   automatically plot, if you wish to see linework, you must call it up
   while using IMVIS (See 'Description if IMVIS Functions').

        3) In IMVIS, vector colors are numbers, not names as in MAPPER. 
   The color numbers are found within the image .PAL file.  You may use
   any of the 255 color numbers available, but it is recommended to use
   the last 16 numbers.  These 16 numbers are added on by the program
   IMG8BIT (which IMVIS uses) and are always the same.  These 16 colors
   are listed above.

        4) For MAPPER, the number of vectors within a set must be given. 
   For IMVIS, the number of vector sets must be given  (VECTOR_SETS = 6
   from above) along with the number of vectors within a set (country = 1
   from above) must be given.




   Example 7:  Earth Located Image -- Mercator Projection & MAPPER Data

        FILE_TYPE          = IMAGE
        IMAGE_LINES        =  256
        LINE_SAMPLES       =  384
        IMAGE_POINTER      = 'aland.img'
        PAL_POINTER        = 'aland.pal'
        SAMPLE_RATE = 1
        Projection = mercator
           30.993814 = Upper Left Pixel Latitude
          -90.410624 = Upper Left Pixel Longitude
            1.25 km = Pixel Size at Equator
        VECTOR_SETS = 5
          county = 1
             l:\geophys\county 120.0 0.0 253
          coast  = 10
             wtrbcb  3.0  0.3  253
             wtrbc  0.3  0.0  253
             wtrb2b  3.0  0.3  253
             wtrb2  0.3  0.0  253
             wtrb3b  3.0  0.3  253
             wtrb3  0.3  0.0  253
             wtrb4b  1.0  0.3  253
             wtrb4  0.3  0.0  253
             wtrb5  0.3  0.0  253
             wtrb6  0.3  0.0  253
          state  = 1
             l:\geophys\state  120.0 0.0 246
          rivers = 1
             l:\geophys\rivers 120.0 0.0 251
          nation = 1
             l:\geophys\nation 120.0 0.0 245
        CHANNEL_INPUT:
             RED   = a900404b.ch2 Range =   0  50 107
             GREEN = a900404b.ch1 Range =   0  59  90
             BLUE  = a900404b.ch1 Range =   0  59  90
        CAPTION = 3 LINES 
        TEXT_COLOR = 248
        TEXT_SIZE = 2
        AVHRR LAC False Color IR
             RED             = a900404b.ch2 Range =   0  50 107
             BLUE and GREEN  = a900404b.ch1 Range =   0  59  90
 
        This label file is similar to Example 6 with two changes.  The
   projection of this image is Mercator.  For this projection, three
   pieces of information are required :

        Upper Left Pixel Latitude
        Upper Left Pixel Longitude
        Pixel Size at Equator

   If you do not know this information than use the label file described
   in Example 5.

        Also, the 'caption' option has been added to this image.  This
   option allows text to be printed on the image.  The caption can be any
   reasonable length, but the number of lines in the caption has to be
   identified in the line :

        CAPTION = n LINES

   Where 'n' is the number of lines.  You must also pick the color the
   caption is to print in.  The color information is found in the image
   .PAL file.  For ease of color identification, use one of the last 16
   colors.  These 16 colors are shown in Example 6.  In the above example,
   the text will plot in color number 248, which is yellow.  Next, you
   must determine the size of the text to be plotted on the screen.  A
   text size of 1 means the following :

        a character is 10 pixels wide and a space is 5 pixels wide
        a character is 19 pixels above the line and 6 below the line (for 
          letters such as 'y' which hang down) for a total of 25 pixels in
          height.

   Generally, a text size of 2 (which means the text is plotted half as
   large) is the must useful.  After the size of the text has been
   determined, the caption itself must be type in.  The caption will be
   plotted in the lower right hand corner of the screen.  The caption
   plots if you do not zoom in on the image or if you chose the 'caption'
   option in the IMVIS menu.  See the section describing IMVIS functions.






                     * * * To View a Single Image * * *


        When you enter IMVIS, you will see an alphabetical list of all
   type '.LBL' files in a window located at the top right part of your
   screen. The window will display a maximum of 19 file names at a given
   time, but up to 300 file names may be present.  You can access the
   extra file names by scrolling the list (arrow keys, 'Pg Dn', 'Pg Up',
   'Home' or 'End') or by typing the file name.  Select a file by 
   positioning the cursor (highlight bar) over the file name and hit
   <enter>.

        To exit the menu without choosing an image hit <esc>.  If you have
   given path options in the command line, the program will search the
   other directories designated in the command line for existing label
   files.  If you continue to hit <esc>, you will eventually exit from the
   program.

        If the label file you chose is for a single image (examples 1,2
   and 4 above) you will leave text mode and go into image mode.  The
   image mode can be forced by entering a slash followed by the letter
   identification (Id).  For example :

        imvis /e

   will force the program into EGA mode.  The available modes are:

       Id  Mode              Columns  Rows  Colors Total Palette
       --- ----------------- ------- ------ ------ --------------
        E  EGA                  640    350     16            64
        V  VGA                  640    480     16        262144     
        S  VGA                  320    200    256        262144
        Y  Extended VGA         640    400    256        262144
        X  Extended VGA         640    480    256        262144

        The program will try to boot the board in the following order --
   X,Y,S,E -- until it finds a mode which can be booted.  The 'V' mode
   must be requested if you wish to use it.  Many of the functions will
   not work in the V and E modes and none of them will work well in the E
   mode.

        The command line 'imvis scan' will cause imvis to scan through all
   the images contained within the working directory.  Each image will be
   displayed for 3 seconds with the image name printed in the upper right
   hand corner.  If a .XMG file for that image does not exist, one will be
   created by IMVIS at this time.  An .XMG file is a screen save of the
   image.  The image will come up on the screen much faster when an .XMG
   file exists.  Also, .XMG files must exist in order to do a histogram
   necessary for creating a color composite image.  See the section
   'To Create an 8-bit Color Image' for more information on this.



                  * * * IMVIS Quick Reference Guide * * *


   SYSTEM       ZOOM       ANALYZE       PLOT        DIGITIZE      QUIT
/Color                   pixel info    boundary        r           r 
r  targa file              histogram     labels.grf      r           r
r                          shade         caption         r           r
r                          smooth                        r       Return to 
r                          rescale                       r       list of all
r                                                        r       .lbl files
r                                                    Give input
(change +/- ,789,123                              filename :
    stretch RGB                                          r
    reset                                                r
    change one color                                     r
    save new table                                       r
    exit color                                     Making binary
                                                      copy of
                                                   <filename>.xyc 
                                                         r
/
r
System     Enter line   Get Line   Zoom      Pan      Line      Quit
cur color       r          r       in                 Color       r
Hide menu       r          r       out                Attrib.     r
Line length     r          r                                    Return to
                r          r                                    list of all
           1st time :      r                                    .lbl files 
           L button down,  (m
           move up + down to                                               r
           change, R button                                                r
           to keep                                                         r
                r                                                          r
/ >1 point - 1 point * 0 points m     r
r                                                   r                r     r
r                                                   r                r     r
r                                                   r                r     r
End+Save   Close+Save  Discard   Edit        Give latitude:        places  r
                       No         r                 r              '*' in  r 
                       Yes        r          Give longitude:       file    r 
                                  r                                        r
/                                        r
r                                                                          r
{
r
Save  Close  Screen    Quit     Line       Add/Delete  Move Point  Snap
Point
             Refresh   Discard  Move       Add Points
             Zoom In   Restore  Color      Double 
             Zoom Out           Attribute  Half
             Pan                Cut        Delete Pt.
                                Shape
                                Area 




                * * * Description of IMVIS Functions * * *


   SYSTEM :
   'Color':
   The following functions alter the color of the image.

         'change +/-,789,123' :
         This allows you to change the color image as a whole.  '+'
         increases the intensity and '-' decreases it.  The number pad    
         controls the hues.  It is operated as follows :
                 Red         Green         Blue
                 ---         -----         ----
                  7            8             9    increases the hue value
                  1            2             3    decreases the hue value
          

         'stretch RGB' :
         If the color image does not use the full range of intensity in   
         its color palette you can stretch the colors.  The option will   
         have no effect on gray tone images.  There is no change in the   
         hues or saturations of the colors.  Only intensities are changed.

         'reset' :
         This will set the palette back to the original.     

         'change one color' :
         If you wish one color on your image to be different, this        
         function allows you to change that one color without changing any
         of the other colors.

         'save new table' :
         After you have altered the image colors, you can save the new    
         palette information in place of the old information.  It is a    
         good idea to save a copy of the old palette file first before    
         using this option.  To save the old palette to a backup file, you
         must exit from IMVIS.

         'exit color' :
         This allows you to exit the color functions and returns you back 
         to the main SYSTEM menu.

   'targa file':
   This allows you to output a 32-bit targa file of the image you are
   working with.


   ZOOM :
   If the image is too large to fit on the screen, a sub-sampled image is
   displayed.  This function allows a selected area od the sampled image
   to be viewed at full resolution.  If the full resolution image will fit
   on the screen, then this option is inoperative.  A box appears on the
   image which represents the size and shape of a full resolution (every
   pixel) sample of the image.  The box can be moved 16 pixels at a time
   in any direction by using the arrow keys.  To change the distance the
   box moves each time use '+' and '-' keys to double and halve this value
   respectively.  The size (not the shape) of this box can be changed by
   using 'l' for larger and 's' for smaller.  Hit <enter> to select a
   potion of the image or <esc> to exit without changing the display. 
   Note, if the zoom box is  made to be smaller than full resolution, the
   box will change color.  Beware of zooming in too far and thus causing
   replication of pixels to occur. 



   ANALYZE :

   'pixel info':
   This puts a cursor in the middle of the screen which can be moved to
   get pixel information.  The cursor is moved with the arrow or number
   pad ('Num Lock' = off) and the amount of movement is controlled with
   '+' and '-'.  The display at the bottom will change with available
   information but it will look something like this:

    x=256 y=416  84  r: 57 g: 31 b: 26
    3520  5120 lat =  47.76468 lon = -126.63266

   Not all images will have all of the above information.  Some will only
   give x and y locations.  In this example the cursor on the screen is at
   pixel (256,416) which is pixel (3520,5120) in the image file.  The
   value of the pixel on the screen is 84 while the value of the red,
   green and blue pixels used to make the color image are 57, 31 and 26
   respectively.  These RGB values come directly from the files used to
   make the composite image and are not scaled in any way.

   'output Targa file':
   This outputs a 32 bit Targa file.

   'histogram':
   This does a histogram of the screen data by dn.  The first choice is a
   box that asks where you want the graph.  Use the following to position
   the histogram box:

        (l)arger
        (s)maller
        (H)igher
        (S)horter
        (W)ider
        (N)arrower
        '+' move more
        '-' move less

   Do not cover data with this box as it will be destroyed (on the screen
   only, not in the file.)  When you are satisfied with the position of
   the histogram box, hit <enter>.  After hitting <enter>, any information
   existing under the box will be blanked out.  Next, a smaller box
   appears on the screen.  This box is also operated by the commands
   above.  After you have sized this box, hit <enter>, the histogram of
   information contained within this box is then graphed in the area
   determined by the first box placement.  To end this function hit <esc>.

   'shade':
   Makes a shaded relief of the image with the light source to the right. 
   This function asks for the contrast value (between 1 and 20).  Trial
   and error will determine which is best, start with a contrast of 10 and
   work from there.

   'smooth':
   Does a 3x3 average of the pixels.  Use this before 'Shade'.


   PLOT :

   'boundary plot':
   If a vector section exists within the image .LBL file, this function
   allows you to plot those vectors.  After you have called this function,
   a menu will appear on the right hand side of the screen with the
   vector sets listed.  Move the highlight bar over the linework you want
   and hit <enter>.  You will see the vector plotted over the image. 
   After they have finished plotting, the menu of vector sets will return.
   Either plot more linework, or exit this function to return back to the
   main menu.

   'labels.GRF':

   'caption':
   If a caption section exists within your image .LBL file, this option
   allows you to plot the caption.  The caption will automatically plot
   on the sub-sampled image, but if you have zoomed into a section of the
   image, then the caption will not automatically plot; you have to call
   it up.  After you have selected the caption function, you will see the
   caption plot in the lower right hand corner of the screen.

   DIGITIZE :
   See the section 'To Digitize Linework' for the description of these
   functions.

   QUIT :
   This returns you back to the listing of all .LBL files within your
   working directory.  You can either view another image by moving the
   highlight bar over the image name and hit <enter>, or you can exit the
   program by hitting <esc>.  You may have to hit <esc> a number of times
   as IMVIS will check the working directory along with any directories
   included in the path for all .LBL files.  Hit <esc> until you see the
   DOS prompt.







                 * * * To Create An 8-bit Color Image * * *


        The following section contains specific references to the images
   [canon02], [canon03], and [canon04]; and to the label file canon.lbl. 
   These files are contained on the 5.25" disks provided.  I recommend
   that you walk through the following section with those files and create
   your own composite image.

        IMVIS allows you to create an 8-bit composite image from a set of
   registered images.  An example of a registered image set, canon.lbl,
   follows (Example 3 above also describes this type of .LBL file) :

      FILE_TYPE          = IMAGE
      IMAGE_LINES        =  400
      LINE_SAMPLES       =  640
      SET_POINTER        =    6
        canon01.dat   0  255
        canon02.dat   0  255
        canon03.dat   0  255
        canon04.dat   0  255
        canon05.dat   0  255
        canon07.dat   0  255
      END
 
   This .LBL file does not contain a pointer to a .DAT file and therefore
   does not display an image on the screen when called.  The above is a
   registered set of 7 images (the seven TM channels) of the exact same
   area.  That is, each pixel of each image has the same latitude and
   longitude value.  

        When you chose this type of .LBL file in IMVIS, the following menu
   appears :

      Display quick color
      Make 8-bit color image
      Make RGB composite file
      Scale image set
      Scan set -- full image
      Scan set -- sub image
      x -- exit
      'Esc'=Quit  'Enter'=Choose file

   (This section describes how to create an 8-bit image.  The rest of the
   functions listed above are described in the following section, 'Other
   Options for a Registered Set Label File'.)  To create an 8-bit image,
   move the highlight bar over that option and hit <enter>.  You will then
   see a list of all the registered images as shown in the .LBL file. 
   This list will be in red.  Chose the image you wish to be the red plane
   of your composite image and hit <enter>.  The list will now turn green;
   chose the image for the green plane and hit <enter>.  Last, the list
   will turn blue; chose the image for the blue plane and hit <enter>. 
   For demonstration purposes, I used 'canon04.dat' for the red plane,
   'canon03.dat' for the green plane, and 'canon02.dat' for the blue
   plane.

        You will then see what you have chosen for the planes and you are
   asked if this is what you want.  If it is, type 'y', if not, type 'n'. 
   After you have chosen your color plane choices, another menu appears
   along with the following information :

      Use current parameters
      Histogram from full image files
      Histogram from sub image files
      Input scale parameters
      Exit scale option


      --------------------------------------
              Current Scaling Parameters
      --------------------------------------
             Minimum   Mid-Point    Maximum
      --------------- ------------ --------- 
      red       0          63         255
      green     0         127         255
      blue      0         127         255


        The above information shows the scaling parameters as given in the
   .LBL file.  If you look at the file canon.LBL, you will see after each
   image file, the numbers 0 and 255.  0 is taken as the minimum and 255
   is taken as the maximum parameter value.

        You now have a number of options.  If you are content with the
   current parameters, you may move the highlight bar over 'Use current
   parameters' and hit <enter>.  You will then be prompted to enter the
   filename you wish for the composite image.  For example, [can_432]
   was created using channel 4 of canon TM data for the red plane, channel
   3 for the green plane, and channel 2 for the blue plane.  IMVIS will
   then call program IMG8BIT which creates the composite image.  You will
   be asked the resolution of the image.  For the first try, it is a good
   idea to use 4 for 1/4 resolution to get an idea of what the image looks
   like.  If it is correct, you can run through all the above steps and
   create the image at full resolution.  This simply saves you a lot of
   time since creating a full resolution image takes a lot of time and if
   the image is incorrect you must go through it all again.

        If you wish to change the scaling parameters, you must first run a
   histogram on the images.  The histogram determines the minimum,
   maximum, and mid-point of each image color plane.  To do this, the
   image .XMG files must be present in the working directory.  (This
   assumes you are operating IMVIS with the /X option mentioned in the
   'Viewing a Single Image' section above.  If you are using the /V
   option, for example, you will need the .MG files and so on.)  
   Therefore, to run this option, you must have already created .XMG files
   for the images you are using as the color planes.  IMVIS automatically
   creates the image .XMG file when you first look at the image through
   IMVIS.  An .XMG file is a screen dump of the image information, so the
   next time you look at that image, it will appear on the screen much
   faster than the first time you viewed it.  To ensure you have all the
   .XMG files, simply view all the images first, and then call the image
   registered set .LBL file.

        You may make a histogram of either the full image or the sub
   image, depending on the level of resolution you require.  Mover the
   highlight bar over the histogram option and hit <enter>.  You will see
   the massage : 'processing <filename>.xmg'  for each of the three color
   planes.  When all three planes have been processed you will see the
   following appear on the screen :

      --------------------------------------
              Current Scaling Parameters
      --------------------------------------
             Minimum   Mid-Point    Maximum
      ------ -------- ------------ --------- 
      red      22          40          56
      green    18          34          49
      blue     18          28          38
      red       0          63         255
      green     0         127         255
      --------------- ------------ ---------
      Use 'Number Pad' to change percentiles
      --------------- ------------ ---------
      up        7           8           9
      --------------- ------------ ---------
              0.05        0.50        0.95    percentile
      --------------- ------------ ---------
      down      1           2           3
      --------------- ------------ ---------

   along with the following menu :

      use as is
      change table
      change image

        If you chose the option 'use as is' you will be returned to the
   previous menu.  At this point, if you 'exit scale option,' IMVIS will
   call the program IMG8BIT and your composite color image will be
   created.

        The option 'change table' allows you to change the percentiles on
   the screen using the number pad.  The 7, 8, and 9 keys on the number
   pad increase the percentile numbers.  The 1, 2, and 3 keys decrease the
   value.  This allows you to manually change the values, but this option
   is not recommended because you have no basis or reference for the
   values.

        The last option 'change image' is the option that is recommended
   to use.  The three channels are shown as they exist in the files, but
   are subsampled to fit on the screen.  When you hit any key, you will
   see the three-point stretch of the images.  Generally, you want this to
   be a linear stretch; that is, you want the middle number to be the
   average of the minimum and maximum numbers.  To do this, move the
   highlight bar by hitting either the <enter> or the backspace keys.  You
   can change the values using the arrow keys.  You will see the effect of
   your changes on the screen as the numbers change.  When you have
   altered the numbers to your satisfaction, hit the <esc> key.  You will
   be returned to the following menu :

      Use current parameters
      Histogram from full image files
      Histogram from sub image files
      Input scale parameters
      Exit scale option

        At this point, you can 'exit scale option' to begin creating your
   color composite image.  You will see a verification of the images and
   color planes, and then you are prompted to give the output image file
   name.  For example :

      Input Images:                      < Verification of images    > 
        RED -- 'canon04.dat'             < and color planes.         >
      GREEN -- 'canon03.dat'
       BLUE -- 'canon02.dat'

      Give output image file name
      can_432                           < The file name I typed in.  >

      Give sample rate (1 = full res, 2 = 1/2 size etc.)
      1                                 < The sample rate I typed in.>

   IMVIS will continue the creation of the composite image without further
   interaction from the user.  As the program works, the screen will fill
   with information describing the process.  This also lets you know that
   the computer is working.  It takes a number of minutes to create a
   composite image.  The information that will fill the screen will look
   something like the following :

      Making 24 bit image file -- 'imvis.cmg' and info file 'imvis.chn'
      sample = 1   offset = 0
        29 of 400
      Dither constant changed from 5.00 to 5.00
      Minimum points to keep set from 1 to 10 
      Maximum colors reset from 255 to 240

      Processing 24 bit image 'imvis.cmg' into 8 bit image 'can_432'.
      row = 400 col = 640
      Loading Dither constants.
      Creating Dithered image.
        29 of 400 
      There are 400 rows and 640 columns.
      Scaling Red, Green and Blue to fit image colors.
      enough colors = 228
      36 red x 44 grn x 27 blu -- 2740 colors
      max discernable colors:
      119.377480 -- red
      158.931797 -- green
      70.978980 -- blue
       8 red x 10 grn x  6 blu -- 138 colors
      10 red x 12 grn x  7 blu -- 217 colors
      11 red x 13 grn x  8 blu -- 266 colors
      Image has 247 colors at 11 x 13 x 7
      Image has 235 colors at 11 x 12 x 7
      Now filling color assignment table.

      Averaging lookup table colors:
      29 of 400
      creating image file
      SAMPLE_RATE = 1
      CHANNEL INPUT :
         RED   = canon04.dat  Range = 11  40  65
         GREEN = canon03.dat  Range = 13  34  61 
         BLUE  = canon02.dat  Range = 15  28  46
      29 of 400 lines.

   At this point, the program has finished and you are at the DOS prompt. 
   A .LBL file for your composite image has automatically been created and
   will look similar to the following  :

      FILE_TYPE          = IMAGE
      IMAGE_LINES        =  400
      LINE_SAMPLES       =  640
      IMAGE_POINTER      = 'can_432.dat'
      PAL_POINTER        = 'can_432.pal'
      PALETTE_POINTER    = 'can_432.pal'
      SAMPLE_RATE = 1
      CHANNEL_INPUT:
           RED   = canon04.dat Range =  11  40  65
           GREEN = canon03.dat Range =  13  34  61
           BLUE  = canon02.dat Range =  15  28  46

   You can now enter IMVIS and view the new composite image by placing the
   highlight bar over the filename and hitting <enter>.  The process of
   creating a color composite image is finished.




          * * * Other Options for a Registered Set Label File * * *


        When you call a registered set label file, there are options
   available to you other than creating a color composite image.  Below is
   the menu displayed after you have called a registered set label file  :

      Display quick color
      Make 8-bit color image
      Make RGB composite file
      Scale image set
      Scan set -- full image
      Scan set -- sub image
      x -- exit
      'Esc'=Quit  'Enter'=Choose file

   'Display quick color' :
   This will make a 7 red by 7 green by 5 blue color image.  After you
   have chosen this function, you will be asked to chose which files you
   wish to use for each color plane.  Next, you will see a listing of the
   files and the respective color planes with the question : 'Is this what
   you want?'  If so, type 'y.'  A color image is displayed on the screen.
   It is not very good, but it shows some color.  This new image is not
   saved -- it is simply a display.  Hitting <enter> will return you to
   the main menu.

   'Make 8-bit color image' :
   This function is described in detail in the preceding section 
   'Creating an 8-bit Color Image.'

   'Make RGB composite file' :
   This function is similar to 'Make 8-bit color image' except a .CMG file
   is created rather than an image.  After you have chosen this function,
   you will be asked to chose which files you wish to use for each color
   plane.  Next, you will see the 'Current Scaling Parameters' (as shown
   in the preceding section) along with the following menu :
      Use current parameters
      Histogram from full image files
      Histogram from sub image files
      Input scale parameters
      Exit scale option
   This menu is operated the same as for the function 'Make 8-bit com-
   posite image.'  If you chose to make a histogram, you can alter the
   parameters by either changing the table or changing the image.  See the
   preceding section.  When you exit the scale option, a .CMG file is
   created.  In order to create an image from the .CMG file, you must
   fully exit IMVIS and run the program IMG8BIT.  This program will create
   an 8-bit image from your newly created .CMG file.  If you type 'IMG8BIT
   <enter>' you will see the following information :
      img8bit [infile] [outfile] <dither> </m min points> </c max colors>

      where  infile -- name of input file of type '.cmg'
            outfile -- name of output file set
             dither -- amount of dithering :  default = 5
         min points -- minimum number of pixels of a color to use
         max colors -- maximum number of colors on final image: default = 
                       256

      example :

      img8bit infile outfile 7 /m 10 /c 240
   The advantage of creating a .CMG file and then running IMG8BIT over
   creating the image in IMVIS, is the ability to change the defaults. 
   When IMVIS calls IMG8BIT, the default dither and max colors are used. 
   When you call IMG8BIT from the DOS prompt, you are able to alter these
   defaults to the needs of your map.  For example, if you have an image
   of a photograph, then an dither value of 5 works well.  If you have an
   image of a geologic map containing the contact points and colored
   formations, then no dither (dither value = 1) is recommended.  After
   you have run IMG8BIT, you can view the image with IMVIS.

   'Scale image set'  :

   'Scan set -- full image' :
   Each image listed within the registered set label file is displayed on
   the screen for three seconds.  The name of each image is printed on the
   upper left hand corner of the screen.  This function allows you to
   quickly scan a set before creating a composite image.  After all the
   images have been shown, the menu will return.  You can not alter the
   images at this point, this is simply a display function.

   'Scan set -- sub image' :
 





                      * * * To Digitize Linework * * *

         Included is an 8-bit color image of a section of a geologic map,
   [geo_map], which was scanned in at 150 dots-per-inch (dpi).  Through
   IMVIS, you can create digitized linework from scanned maps.  This
   linework can then be converted to latitude and longitude data and used
   with MAPPER and LINEFIX.

        To digitize linework, move the highlight bat over 'DIGITIZE' and
   hit the left mouse button.  The prompt 'Give input filename' will
   appear in the upper left hand corner of the screen.  (To see the given
   example, type 'geo') With the keyboard, enter the filename.  After the   
   
   message 'Making binary copy of <filename>.xyc' disappears, you will
   then see another menu appear at the top of the screen.  The options 
   available to you from this menu are :

   System
      cur color  -- Allows you to change the cursor color.
      hide menu  -- Hides the menu so you can see the entire screen   
                    while you are digitizing.
      LineLength -- In order for this function to work, the image .lbl file 
                    must be altered.  The algorithm used to calculate the   
                    line length uses the scan rate of the image (dpi) and   
                    the scale of the image.  This latter bit of information 
                    is found by running LATLON on the .xyc file.  LATLON    
                    creates text file of the same filename as the .xyc file.
                    In this text file, you will see the scale information.  
                    Append this information to the image .lbl file after    
                    the PALETTE_POINTER line :
                          SCAN_RATE = 150 DPI
                          IMAGE_SCALE = 930595:1
                          (the numbers given above are examples)
                    After you have altered the .lbl file, re-enter IMVIS and
                    call up the .xyc file.  While in this function, move the
                    cursor to the line and hit the left mouse button.  The  
                    line will highlight and the length will be displayed in 
                    the bottom left hand corner.  If you continue to        
                    highlight lines, the length of the individual line will 
                    be displayed along with the total length traversed.
    Enter Line   -- See below for the options available from this     
                    function.
    Get Line     -- Edit a previously digitized line.
    Zoom 
      in         -- Zooms into the image.
      out        -- Zooms out of the image
    Pan          -- Pans the screen in reference to cursor.
    Line
      Color      -- The following message appears in the lower left hand    
                    corner of the screen : 0  L button down, move up + down 
                    to change, R button to keep.  While depressing the left 
                    mouse button, move the mouse up and down, you will see  
                    the color and number change on the screen.  When you    
                    have the color you want, release the left button and    
                    depress the right mouse button.  The line color will    
                    then be that color.  Subsequent digitized lines will be 
                    this same color unless you invoke this function again   
                    and alter the color.
      Attrib.    -- This allows you to separate the lines by an attribute   
                    identifier.  If the line is bathymetry, for example,    
                    then you can distinguish the line by its depth value.
    Quit         -- Returns you to the main menu.

   Enter Line :
   When you chose the 'Enter Line' function, a number of options become
   available depending on what you have previously entered :

     1) If you have not yet chosen a line color, then the following prompt  
   appears in the lower left hand corner of the screen  '0  L button        
   down, move up + down to change, R button to keep'.  While depressing     
   the left mouse button, move the mouse up and down, to see the color      
   and number change on the screen.  When you have the color you want,      
   release the left button and depress the right mouse button.  The line    
   color will then be that color.  Subsequent digitized lines will be
   this same  color unless you invoke this function again and alter the     
   color.  You must enter a color from the image palette file.  The         
   following is the list 16 colors contained in the file 'geo_map.PAL'.     
   I recommend that you use colors from the last 16 in the palette file     
   as these are placed there by IMG8BIT or TGA2LBL and are constants.

            Attribute   R    G    B
            ---------  ---  ---  ---
               241      46   46   46
               242     128  128  128
               243     255  255  255
               244     105   90   75
               245     130  111   93
               246      96   28   14
               247     255    0    0
               248     255  128    0
               249     160  160    0
               250       0  200    0
               251       0  120    0
               252       0   72    0
               253       0    0  200
               254       0   20   60
               255     255    0  255 


      2) To enter control points, move the cursor to a graticule point and
   hit the left button on the mouse only once, then hit the right button. 
   You will see the prompt 'Give latitude:'  Key in latitude value and hit
   <enter>.  The prompt 'Give Longitude:' will then appear.  Key in the
   longitude value and hit <enter>.  After both the latitude and longitude
   have been entered, you will again see the cursor on the screen.  Continue
   on until all control points have been entered.  Enter the control points
   before you digitize the lines; the control points must be at the very
   beginning of the .XYC file.


      3) If you do not enter any points, that is, you immediately hit the   
   right button on the mouse, then an asterisk (*) will be placed in the    
   file.  The file format for the control points of an .XYC file is :

        47 17
         47.0000   21.3333
        47 18
         350.6667  30.0000
        46 18
         340.3333  466.0000
        46 17
          31.3333  456.3333
       *

   Where the first line is the latitude and longitude and the second line
   is the corresponding x and y.  The '*' marks the end of the control
   point section of the .XYC file.  



      4) If you have previously entered an attribute or color, you will see 
   a cursor on the screen.  If you have entered your control points, move   
   the cursor over the point at which you wish to begin the line and hit the
   left button on the mouse.  Move the cursor along the line and hit the    
   left button as many times as necessary to define the line.  To end the   
   line, hit the right button.  You will then see another menu at the top of 
   the screen :

          End+Save   -- Ends the line and adds it to the file imvis.XYC
          Close+Save -- Connects the first and last point od the line and 
                        adds it to the file imvis.XYC.
          Discard
             No      -- The line will be kept in the .xyc file.  This is a  
                        safeguard feature in the event you inadvertently    
                        invoked this function.
             Yes     -- The line will not be added to the file imvis.XYC. 
                        It will remain on the screen, however, until the  
                        screen is redrawn by either pan, zoom or refresh.
          Edit       -- See the options below.



   Edit :
   If you chose to edit the line you have just digitized, the line will
   turn black with the points in white.  You will see the following menu
   at the top of the screen :

          Save            -- Changes made to the line will be saved and     
                             added to the file 'imvis.XYC'.
          Close           -- The first and last point of the line will be   
                             connected.
          Screen
            Refresh       -- Redraws the screen at the current zoom.  No    
                             previously discarded lines will appear.
            Zoom In       -- Zooms into the image. 
            Zoom Out      -- Zooms out of the image
            Pan           -- Pans the screen in reference to cursor.
          Quit
            Discard       -- Does not enter the line in 'imvis.XYC'
            Restore       -- Restores a previously discarded line provided  
                             the screen has not been refreshed or zoomed in 
                             or out.
          Line
            Move          -- Pick a point on the line, then move the cursor 
                             to where that point should be and hit the left 
                             button.  The entire line is moved that amount.
            Color         -- The color of the line can be changed as        
                             described above.
            Attribute     -- The attribute of the lien can be changed.  This 
                             is useful for topography, bathymetry, or       
                             gravity for example.  The line can be defined  
                             by attribute rather than by color.
          Add/Delete
            Add Points    -- Adds points to the line.
            Double        -- A point is added in between all existing       
                             points, thus doubling the number of points in  
                             the line. 
            Half          -- Every other point is removed from the line     
                             except for the first and last points.
            Delete Points -- Deletes the chosen point from the line*.
          Move Point      -- Moves a point on the line from it's original   
                             position to the position of the cursor.
          Snap Point      -- Connects the chosen point from the line being  
                             edited to the nearest point of another line.   
                             Ideal for 'w' type junctions.

   *  A chosen point has a little white box drawn around it.



   Get Line :
   This function gives you the editing menu as shown above.  By this, you   
   are able to edit a line that has been previously digitized.  This is most 
   helpful in the 'Snap Point' option.  In order to create a 'T' junction   
   between lines, a point must be located at that junction.  If a point is  
   not at the junction, when you chose 'Snap Point', the junction will look 
   'Y'shaped.  While digitizing, it is easy to forget to put a point at     
   every line junction.  The 'Get Line' function allows you to edit a line  
   and add a point where needed in addition to all the other editing        
   options.


   When you have finished digitizing, exit out of IMVIS.  You will see the  
   following prompt :

          Do you wish to replace '<filename>.xyc' (the original data file)
          with 'imvis.xyc' (the updated file)?  (y or n)

   If you type 'y', then all new changes made will be added to <file        
   name>.XYC. If you type 'n', you will see :

          All changes are only in 'imvis.xyc'
          No changes have been made to '<filename>.xyc'
 
   To view the linework in MAPPER or LINEFIX, convert the .XYC file to a    
   .RAW file using LATLON.  For further information on LATLON and the       
   related programs, see the 'Demonstration Disk for USGS-OEMG Mapping      
   Software'. [mapper00] shows what the final product of [geo_map] looks    
   like.