Image Processing Reference
In-Depth Information
Figure3.14 Airborne radar system schematic.
spacecraft can create images of Earth's surface (or other planets) by data processing
millions of return pulses. The movement of the platform carrying the radar system
defines one axis of scan; the image builds up along the direction of flight.
Military radar systems development has resulted in many commercial and
scientific applications for radar, and the recent advent of small, high-speed
computers has made it possible to generate three-dimensional radar images that
require sophisticated image processing. Early radar images tended to be difficult
for untrained observers to interpret, largely owing to the unavoidable presence of
noise in the radar image caused by scattering of the radar signal by atmospheric
phenomena or flocks of birds. It is now possible to eliminate a great deal of this
“clutter,” as it is called, by using advanced data processing techniques and special
antenna hardware.
Recall from the last chapter that electromagnetic waves are scattered weakly
when they pass through a non-conductive material that consists of particles that
are much smaller than the wavelength of the electromagnetic waves. Because of
this property of waves, imaging radar can penetrate through jungle vegetation, ice,
snow, and dry sand and soil, revealing concealed or buried objects hidden to our
eyes, and in many cases also hidden to infrared and ultraviolet imaging systems.
This has led to the use of imaging radar in the field of archaeology. Large-scale
archaeological sites are often obscured by windblown sand or vegetation, making
them very difficult to study with conventional aerial photography. Imaging radar
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