Remote sensing is a field of technology designed to enable people to look beyond the range of human vision. Whether it is over the horizon, beyond our limited human range, or in a spectral range outside human perception, we are in search of information. The focus here will be on imaging systems that extend our range of perception, particularly in the realms of intelligence, strategy, tactics, and military applications.
To begin, consider one of the first remote-sensing images. Figure 1.1 shows a photograph by Gaspard-FÃ©lix Tournachon (Gaspard was also known by his pseudonym, Nadar). Gaspard took this aerial photo of Paris in 1868 from the Hippodrome Balloon, tethered 1700 ft above Paris. Contrast this with the cover photo taken by Apollo 17, just one hundred years later.
This is a fairly classic remote-sensing imageâa representation from a specific place and time of an area of interest. What sorts of things can be learned from such an image? Where, for instance, are the streets? What buildings are there? What are the purposes of those buildings? Which buildings are still there today? These are the elements of information that we want to extract from our imagery.
In the material that follows, a model is established for extracting information from remote-sensing data. Following that section, remote-sensing data from a variety of systems is introduced to provide an early overview of the domains of the field.
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