Contour Plot Smoothing
The examples below show the effect of changing the
Smoothing parameter on the generation of image contours. The
smoothing parameter controls the stiffness of the contours—in other
words how sharp a corner the contour curve can turn when snaking
through noise. This example shows the
interactive contour method, but the
Smoothing parameter is also used by
the
Contour Plot command. The smoothing becomes
especially important in reducing the tendency toward false contours
of noise when contouring near the background.
What Not to Do
First, let's see what not to do when plotting
contours — at least for typical applications. First, remember that
most astronomical data are noisy, and plotting exact contours may
track the noise and give erratic excursions from the true,
noiseless value. In the picture below, Smoothing = None was used and the contour was
marked at a very low brightness level where the image is dominated
by noise. There is no useful information in this plot and it
requires a lot of CPU time to redraw the window. However, there
could be useful information from a contour drawn at the same level
but using amedium or high smoothing value.
Tip
|
You can terminate the contour computation at any
time by hitting the [Esc] (Escape)
key. This is especially handy if you start a contour computation
after accidentally clicking on a level too far into the noise.
|
To control the effect of false contours created by
image noise, try one or both of the following strategies:
Examples of Contour Smoothing
In the examples below, the contour was drawn at a
higher intensity level where the differences between the smoothness
settings are are more easily seen. All other contouring Properties
are the same. To create these plots, the
Interactive Contour Plot Properties dialog was
used to repeatedly change the contour Smoothness, then click [Apply].
No smoothing:
|
Low Smoothing:
|
|
|
Medium Smoothing:
|
High Smoothing:
|
|
|
Related Topics
Contour Plot
Interactive Contour Plotting
Interactive Contour Plotting Properties
Mira Pro x64 User's Guide, Copyright Ⓒ 2023 Mirametrics, Inc. All
Rights Reserved.
|