Page 52 - Digital Analysis of Remotely Sensed Imagery

CHAPTER 2

Overview of Remotely

Sensed Data

n the late 1960s, meteorological satellite data with a coarse
spatial resolution from instruments such as the Advanced Very
IHigh Resolution Radiometer (AVHRR) from the National
Oceanographic and Atmospheric Administration (NOAA) came
into existence for the first time in history. These data, initially designed
chiefly for the purpose of studying weather conditions, were not
accompanied by wide practice of digital image analysis in the remote
sensing community, due probably to the fledgling state of computing
technology back then. In the early 1970s, the Landsat program was
initiated to acquire satellite data for the exclusive purpose of natural
resources monitoring and mapping. Since then tremendous progress
has been made in remote sensing data acquisition, with tens of
satellites launched. The advance in our data acquisition capacity is
attributed largely to the progress in rocket technology and sensor
design. Consequently, a wide range of satellite data has become
available at a drastically reduced price. Over the years the spatial and
spectral resolutions of these data have been improved. Satellite data
of a finer spatial resolution have opened up new fields of applications
that were not possible with data of a poor spatial or spectral resolution
before. In addition to multispectral data, it is possible to obtain
satellite data in hundreds of spectral bands. These remotely sensed
data with improved viewing capabilities and improved resolution
have not only opened up new areas of successful applications, but
also created specific fields in digital image analysis.
In this chapter, these satellite data are comprehensively reviewed in
terms of their critical properties and main areas of application. All the
satellite data, including meteorological, oceanographic, natural
resources, and even radar, will be covered in this overview. Both
multispectral and hyperspectral data are included in this review. In
addition, this chapter also identifies recently emerged trends in satellite
data acquisition, including the acquisition from airborne platforms.
This identification is followed by a discussion on how to convert existent
25