.LP
When the Color Mesh or Surface plot types are used, the imagery data is draped
over the elevation data.  However, in the event that you would like to display
the elevation data as it would be displayed in the \fBxprism3\fP plotting 
package (that is, with colors indicating depth rather than a draping of the
image data) you may click on the "Use Imagery" logical, changing it to False.
.SH
Interpolate Imagery:
.LP
This option causes \fBviewimage\fP to use an interpolation algorithm to do a
much more accurate draping of the imagery over the elevation data.  It is 
time consuming, although many users may feel that the increased
quality of the displayed imagery is worth the wait.
.SH
Proportional Plotting:
.LP
.sp
This option causes the elevation data to be mapped to a unit cube;  that is,
it normalizes the X, Y, and Z information to be equidistant values.
The default value is TRUE.  Remember that if you want the actual X, Y, and
Z values of your elevation data, you must specify this option as FALSE.
.SH
Sub-Sample Factor:
.sp
.LP
The sub-sample factor is used in the same way as it is in \fBxprism2\fP & 
\fBxprism3\fP.  The sub-sampling factor allows you to plot a portion 
of data rather than the entire image.  This is useful when trying to view 
large images which may take a lot of time to render.  For example, using
a sub-sample factor of 2.0 will cause \fBviewimage\fP to plot every other 
point in the image, thus plotting a forth of the entire image.  By using 
the sub-sample factor, the user shrinks the amount of data that \fBviewimage\fP
must render;  this in turn will increase the interactiveness of the program.  
It is recommended that you use this feature while viewing the image with 
perspective or readying it for output.  Then, if you want a high quality 
output, you can change the sample factor to 1.0 and the interpolate imagery 
to TRUE; but be aware it may take as much as an hour for a 512x512 image 
to plot.
.SH
Height Factor:
.sp
.LP
The height factor can be used to scale the height (or Z values) of the
elevation image.  This is useful if you wish to exaggerate the height of the
plot, accentuating peaks and valleys, or if you wish to scale down the plot 
to produce a smoother terrain.  A height factor of 2.0, for example, will cause
the image will appear to double in height;  a height factor of 0.5 will cause
the plot to appear only half of it's original height.
.SH
PLOT TYPE
.LP
Use the "Plot Type" toggle to select the type of plot you in which you would 
like to display the elevation data.  The following is a list of the different
plot types that are available:
.sp
.LP
.IP "3D: "
3D plots are comprised of a line connecting each elevation value along 
the X axis.  The plot is formed of a series of connected lines stacked 
in the Y direction.
.IP "Scatter: "
Scatter plots interpret elevation data as a set of individual points, and
are displayed as such.
.IP "Impulse: "
Impulse plots are formed by extending a line from the floor of the elevation 
data, which is usually the X-Y plane, upward in the Z direction.  The height of
each line in the plot represents the value at that particular location.
.IP "Mesh: "
Mesh plots are much like 3D plots, but are pictured as a surface made up
of polygons according to the elevation data rather than as a set of lines.
.IP "Horizon: "
A Horizon plot is a surface plot that is drawn from the rear to the front.
This implies that the under surface will be filled.
.IP "Surface: "
Surface plots are similar to Mesh plots, except the surface is displayed using
the imagery data.
.IP "Contour 3D: "
3D Contour plots are similar to 2D Contour plots in that the contour lines
supply depth information; however, the 3D information is not
cast onto the XY plane, but is left in three dimensions. The different
contour levels are represented by their colors, but depth information provided
by the elevation data is also represented by their position in the 3D space. 
.IP "Contour 2D: "
2D Contour plots are a special case, as they take three dimensional
information but are displayed in a two dimensional space. Contour plots
cast the elevation data onto the XY plane; the contour lines on the XY plane
supply depth information, as in aerial photography and relief
maps.  On a color display, the different contour levels are represented in 
different colors, in ROYGBIV order (red, orange, yellow, green,
blue, indigo, violet), where violet represents the smallest depth value
(Z value) and red represents the largest depth value (Z value).
Unfortunately, contour maps loose much in the translation to a
monochrome machine, as there is no way represent depth.
.IP "Color Mesh: "
Color Mesh plots are similar in structure to Mesh plots, except that the
lines making up the mesh are colored according to the imagery data provided.  
