Page 28 - Digital Analysis of Remotely Sensed Imagery

CHAPTER 1

Overview

igital processing of satellite imagery refers to computer-
based operations that aim to restore, enhance, and classify
Dremotely sensed data. It may involve a single band or multiple
bands in the input, depending on the nature and purpose of the
processing. The output image is a single band in most cases. Digital
analysis of remotely sensed data has a relatively short history. It did
not come into existence until the early 1970s with the launch of the
first Earth Resources Technology Satellite (subsequently renamed
Landsat), when remote sensing images in the digital format became
available for the first time in history. The availability of a huge
quantity of data necessitated their timely and efficient processing. In
response to this demand, digital analysis of remote sensing data
experienced exponential development. In its early years, digital
image analysis was very cumbersome to undertake because the
computer had limited functions and capability. Undertaking of digital
image analysis was made more difficult by the minicomputer running
the user-unfriendly UNIX operating system. Over the years digital
image analysis has become increasingly easy to perform, thanks to
advances in computing technology and in image analysis systems.
Now more processing functions can be achieved at a much faster
pace than ever before.
This chapter introduces the main characteristics and components
of a digital image processing system. The nature of digital analysis of
remote sensing images is summarized comparatively with that of the
familiar visual image interpretation. Following this comparison is a
comprehensive review of the entire process of digital image analysis
from data input to results presentation. Presented next in this chapter
is an introduction to the preliminary knowledge of digital image
analysis that serves to lay a solid foundation for discussion in the
subsequent chapters. Featured prominently in this section are pixels,
the building blocks of satellite imagery. Lastly, this chapter introduces
the important properties of satellite data, such as their spatial and
spectral resolutions, in detail. This chapter ends with an overview of
the content of the remaining chapters in this book.

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