Page 20 - Digital Analysis of Remotely Sensed Imagery

Preface

igital image analysis is a field that crosses the boundaries of
several disciplines. Digital analysis of remotely sensed data
Dfor managing the environment of the Earth and its natural
resources, however, differs from medical image processing and imag-
ing processing in electrical engineering in three ways. First, the object
of study is different. Satellite images are snapshots of the Earth’s sur-
face, which lies in a state of constant change. These changes need to be
monitored from multitemporal images to identify the longitudinal
trends. Second, the data used are captured over a much longer wave-
length range, extending into the thermal infrared and microwave
spectrum, usually recorded in the multispectral domain. Their en-
hancement and classification require an understanding of the interaction
between solar radiation and the Earth’s surface. Finally, the objective
of image analysis is different. A very significant component of digital
analysis of remotely sensed data is to convert them into useful infor-
mation on land cover/land use over the Earth’s surface. The derived
information is usually presented in graphic (map) format at a certain
scale. In order to make the map conform to certain cartographic stan-
dards, image geometry and the accuracy issue must be addressed and
featured prominently in digital image analysis. This book aims at pro-
viding exhaustive coverage of the entire process of analyzing remotely
sensed data for the purpose of producing an accurate and faithful rep-
resentation of the Earth’s resources in the thematic map format.
Recent years have witnessed phenomenal development in sensor
technology and the emergence of a wide variety of remote sensing
satellites. Now it is possible to acquire satellite images with a spatial
resolution as fine as submeters or comparable to that of airborne
photographs. The wide and easy availability of remote sensing data
from various sensors in the digital format creates an ideal opportunity
to process and analyze them automatically. Satellite data are routinely
analyzed using various image processing systems to fulfill different
application needs. The functionality and sophistication of image
analysis have evolved considerably over the last two decades, thanks
to the incessant advances in computing technology.

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