Help for DVECTOR

    dvector can draw any number of vectors on a picture of any size.
Vectors are drawn from the left tiepoint location towards the right
tiepoint location. The left coordinate will have a 3 by 3 pixel cross
at that location. The right coordinate will be at the vector tip IF
EXAG is defaulted to 1.0. Otherwise the vector will fall short or
cross over the right point.
    Vectors come from the second (and beyond) input files in mark
format. They are essentially tiepoints in the order:
left_line, left_sample, right_line, right_sample.
    Internal image storage is as integer*2 so real images will
be rounded.
    Dvector uses a storage buffer of 500000 integers. It will process
all the vectors for each image buffer, making as many passes as
required to process the entire input taken 500000 pixels at a time.
    Up to 100 mark files can be input to DVECTOR. An X will be drawn
at the base of the vector for only the first mark files vectors.
All mark files must be identical in size and number of tiepoints.

If DN is negative:
1. Vectors are drawn on an image of zero dn.
2. Vectors are written from 1 to 255 dn representing angles from 0
   to 360 degrees.
3. No X is drawn at the vector base.


Example:
       dvector in,points out parameters
  where: IN is an input image to superimpose vectors upon.
         POINTS is a MARK file containing the vectors to draw.
          Mark files contain 512 byte records of real*4 data.
          Coordinates are stored in groups of 4 words in the
          order left_line,left_sample,right_line,right_sample...
         OUT is a copy of IN with superimposed vectors.

EXAMPLE:
  (one mark file)
      tracker a,c t
      dvector a,t b
  (two mark files)
      tracker2 c,d,t tt
      dvector a,t,tt b

HISTORY

Written By: J Lorre			    1 AUGUST 1978
Cognizant Programmer: J Lorre
REVISIONS:
03 Oct 94 CRI Made portable for UNIX ... Jim Turner (CRI)
29 Aug 01 GMY Fixed bug to allow use of all 500,000 bytes of buffer allocated.

PARAMETERS: