Page 134 - Digital Analysis of Remotely Sensed Imagery

CHAPTER 4

Image Processing

Systems

ince their advent, digital image analysis systems have undergone
revolutionary changes. In the mid-1980s when digital image pro-
Scessing was still in its infancy, satellite data were analyzed in
microcomputer-based image analysis systems comprising a few sepa-
rate but linked components. A monitor was reserved for user interface
with the system and another monitor for displaying images. Needless
to say, these command-driven systems running in the VAX and later
the UNIX environment were user-unfriendly and cumbersome and
inefficient to operate. Since then digital image processing systems have
greatly improved their performance and functionality owing to the
advances in computing technology in direct response to the need for
efficiently processing a huge quantity of remote sensing data. The early
generation of primitive image processing systems has evolved into
sophisticated icon-driven desktop ones. Running in the Windows XP
environment, these advanced systems are capable of performing mul-
tiple geospatial tasks, one of which is image analysis. Accompanied by
these advances are considerably improved and expanded analytical
functionality of image processing, as well as great ease and flexibility
of operation. Many peripheral processing functions, such as postclas-
sification filtering and raster-based spatial data analysis and modeling,
can be performed in one system. Moreover, results from one system
can be exchanged or integrated with others from another system at
will. A number of mature image processing systems are available for
the explicit purpose of analyzing and visualizing remotely sensed data.
This chapter presents a comprehensive overview of the leading image
analysis packages currently on the market. The criteria for inclusion in
this overview are the image analysis functions. Although the ELT/5500
system has some image manipulation capabilities, such as contrast
enhancement and geoprocessing (e.g., image registration and coregis-
tration), it will not be covered because it lacks image classification
capability. Since one system is able to perform many geoinformatic
functions, some of which may not be related closely to image
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