This program will display cubes and allow for interactive analysis. Although the program
comprises a number of individual tools to perform analysis on your data, only the Spatial
Plot Tool is discussed here until further notice.
Spatial Plot Tool
This tool is used for analyzing manually selected pixel DN values. It works with two
different modes: linear and rotated rectangle. It is also capable of handling three different
modes of interpolation: Nearest Neighbor, BiLinear and Cubic Convolution.
Linear
This mode involves drawing a
line across an open cube. The selection is started by clicking and holding the mouse where
you would like to start your calculations, at which point you may drag the mouse in any
direction and release the click to establish the end of your selection.
The tool calculates the length of the line in pixels, rounding to the nearest full pixel
value. It then divides the actual length of the line by this rounded length to achieve a
step-size. Please note: This step size may be slightly bigger or smaller
than a pixel length, but this difference becomes negligible for larger selections. For
example, if the length of the drawn line was 2.91 pixels, the tool would round the length to
3 and the step-size would be 2.91/3 (or 0.97).
A plot window will be generated with the calculated DN values of the pixels. The first value
to be calculated is the value where the original mouse click was made. At each increment,
according to step size, the tool calculates the value along the line until it reaches where the
mouse-click was released. This means that for a line with a rounded length of 3, the plot would show a
total of 4 plotted DN values. Please note: For a line with a rounded length of
n, the tool will calculate n + 1 values.
Rotated Rectangle
This mode of the Spatial Plot Tool involves drawing a
rectangle across an open cube. The selection starts by clicking and holding the mouse
where you would like to start your calculations, at which point you may drag the mouse in any
direction and release the click to establish one edge of your selection. You may then
drag the mouse away from this original line to expand in the other direction. A single mouse
click establishes your final selection. Please note: The tool will lock
angles to be perpendicular and so your selections will always be a perfect rectangle.
Similar to the linear mode of this tool, the lengths of the lines in pixels are rounded to the
nearest full pixel value, and then the lengths are divided by their rounded lengths to establish
a step-size. Please note:
The step-size along one edge of the selection may differ from the step-size of the
perpendicular edge, this becomes negligible for larger selections. For
example, if the length of the line in one direction was 2.91 pixels, the step-size would be 2.91/3
(or 0.97), whereas if the length of the line in the perpendicular direction was 4.92, the step
size would be 4.92/5 (0.98).
A plot window will be generated with the calculated DN values. This is done by calculating the
value where the original mouse click was made, then continuing in the direction of that
first-drawn line, calculating the DN value at each step-sized increment until it reaches where
the original mouse-click was released. The tool will then calculate the average of these
values. This average becomes the first value in the plot.
The tool will then shift a step-size along the perpendicular edge, and calculate the average DN
value along a line running parallel to the first-drawn line. This average becomes the second
value in the plot. The tool continues this pattern until it has reached the opposite edge of
the rectangle as the first-drawn line.
Interpolations
Spatial Plot Tool makes use of Nearest Nieghbor, BiLinear and Cubic Convolution interpolations
when calculating the DN values at particular points. Do be aware that when the tool is
calculating a DN value at a particular point, it is calculating the interpolated DN value at
that point.
