MAP_POLAR /BACKGROUND

        [ADVANCED\]MAP_POLAR  GenericBegin  [GenericEnd]  /BACKGROUND  Type [Min
    Max] [/STEP Step Xfirst Yfirst]

    Show the polarization vectors derived from the Polarization Angle and  Frac-
    tion maps overlaid on a background image.

    Type can be I for total intensity, F for fractional polarization in percent,
    or  P for the polarized intensity. Min and Max indicate the SCALE to be used
    for the color scaling (through a temporary assignments of the  SCALE  values
    for SHOW command called by MAP_POLAR).

    Type,  Min, and Max, like Step, Xfirst, Yfirst are "sticky" (remanent): they
    keep the previous value until a new one is specified, or are reset to  their
    default  values by use of the /COMPUTE option.  Default is I for Type, 0 for
    Min and Max, which implies an automatic scaling to the data range.