U.S. DEPARTMENT OF THE INTERIOR / U.S. GEOLOGICAL SURVEY
                              
                              
     U.S. GEOLOGICAL SURVEY DIGITAL DATA SERIES DDS-13
                              
           International Phase of Ocean Drilling
             Seismic Line 1 Demultiplexed Data
            Cape Hatteras to Mid-Atlantic Ridge
                              
                              
                           OBPLOT


INTRODUCTION

     OBPLOT is an interactive DOS utility which will
translate a PCX-format graphic image file of observer logs
stored on the CD-ROM into a temporary binary file, and
display that binary file to the user's personal computer
(PC) display.


OVERVIEW

     OBPLOT will query the user for the CD-ROM drive letter,
the PCX file to view, and the drive letter for the drive on
which to create the temporary binary file.  After the user
has answered those queries, OBPLOT will open the indicated
PCX file and translate its contents into a temporary binary
file stored on the indicated drive.  After converting the
PCX file into the temporary file, OBPLOT will query the user
for the display resolution: VGA or Super VGA.  With the
selection of the viewing resolution, OBPLOT will display the
whole graphic image to the user's PC display.  The image
displayed will have a "selection box" over a portion of the
display.  The user may use the keyboard arrow keys to move
the selection box around the displayed image to select a
portion to be displayed at a greater resolution.  OBPLOT
will display that portion of the image at the "zoomed"
resolution.  After the zoomed panel has been displayed, the
user may scroll horizontally and vertically, zoom in or out
of the selected portion, select another portion to display,
or quit the current display.  If quitting the current
display, the user will be queried about whether to display
another PCX image or exit the program.


PROGRAM STARTUP AND FILE SELECTION

     OBPLOT may be started from the DOS prompt by typing
OBPLOT and pressing ENTER.  OBPLOT will display a menu of
CD-ROM drive letters and prompt the user to use the arrow
keys to select the letter representing the CD-ROM drive and
press ENTER.  OBPLOT will go to the OBLOGS subdirectory on

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the CD-ROM, display a menu of PCX format files available,
and prompt the user to highlight the desired file using the
arrow keys and then to select the file by pressing ENTER.
With the selection of the PCX file to translate, OBPLOT will
prompt the user to select the letter of the drive that will
receive the temporary file containing the translated image.
The drive letter is selected in the same manner as described
above for the CD-ROM drive letter.  After the user has
entered this information, OBPLOT will open the indicated PCX
file and translate it into a file named "OBTEMP" on the
drive indicated to receive this file.


VIEWING THE IMAGE

     After the translation of the PCX file into the
temporary file, the user is presented with a viewing
resolution menu and prompted to select the desired viewing
resolution: VGA or Super VGA.  With the selection of the
display resolution, the whole PCX image will be drawn on the
PC's display and the selection box placed in the upper left-
hand portion of the image.  The selection box may be moved
about the image using the arrow keys.  Once the selection
box is placed in the desired location and ENTER is pressed,
OBPLOT will display that portion of the image at a higher,
or zoomed, resolution.  The user may scroll this image
horizontally and vertically using the arrow keys, zoom into
the display using the F5 key, zoom out of the display using
the F6 key, or select another portion for viewing by
pressing the F4 key.
























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EXITING THE PROGRAM

     The user may exit viewing the image by pressing the ESC
key.  A menu will then appear that will allow the user to
select another PCX image to display or to exit the program.
Selecting to view another PCX file will display the file
selection menu.  Selecting to exit will return the user to
the DOS prompt.















































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