Abstract
This research project tested the quality of
DIRSIG's texture characterization routines for a grass target and potential
techniques to improve it. The objective of the DIRSIG is to produce output
images that are analogous to real image outputs so the model can be applied
to a wide range of problems. It is very important that both spectral and
spatial properties of targets are modeled correctly to obtain realistic
results.
DIRSIG applies texture to each pixel
spectrally. Current techniques examine only one bandpass region,
using statistical means to compare a texture image in that bandpass with
a spectral database in order to determine which curve will be used for
a particular pixel. The research in this project examined the quality of
this procedure, and several potential methods for improvement.
DIRSIG images were generated to simulate
two different scenes for which real images exist. ENVI’s principle components
analysis utility was than used to quantify the information in each image
for comparison. Modifications were than made to the process to expand the
spectral database, and incorporate a new algorithm into DIRSIG that examines
multiple bandpass regions when determining which spectra to use for a pixel.
The output for each of these new scenarios was than tested for comparison
with DIRSIG’s previous results, and the results obtained for the truth
images.
This research has quantitatively examined
the ability of DIRSIG to replicate real world texture characteristics,
specifically for a grass target. Research discovered a large gap between
the amount of information that is contained in images of real world data
and those simulated by DIRSIG. Expanding the spectral database did produce
a slight increase in results, increasing the qualitative appearance of
the image as well. The amount of data contained in the DIRSIG image remained
significantly less than that contained in the real image. Increasing the
number of bandpasses employed by DIRSIG in determining which spectra to
map onto a particular pixel, results indicated two different concepts.
Adding one band increased the ability of DIRSIG
to map correctly choose the spectra. Additional bandpasses may increase
the quality of an image, however, choosing too many bandpass regions for
an image can cause the resulting quality of the image to decrease. The
process is very complex, the output quality is dependent on the particular
imaging system that is being modeled, the bandpasses that are chosen, and
the amount of bandpasses that are used as references.
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