Environmental Engineering Reference
In-Depth Information
FIGURE 2.5 (Color Figure 2.5 follows page 396.)
False-color satellite image of northern New Jersey (ERTS-1, 1972). (From EROS Data Center, 1972.)
missions are practical. One imaging system available is composed of a digital
camera, onboard GPS, and inertial measurement unit. The digital camera collects
imagery in three bands and can provide both true color and color infrared.
Images are obtained with resolutions of 0.3 to 1 m, and stereo-images are possible
(Professional Surveyor, 2002).
Airborne Imagery (Radar Sensors)
SLAR ( side-looking airborne radar, real-aperture system) has been in use for many
years. It penetrates cloud cover and to some degree vegetation, providing low-
resolution images normally at scales of 1:125,000 to 1:100,000, and occasionally
smaller (see Figure 2.6 and Figure 6.4). Worldwide coverage, including the
United States, is spotty.
LiDAR (light detection and ranging, or laser radar; GPS based) : This airborne system
sends out pulses of laser energy to the ground surface that reflect the energy, pro-
viding a measure of the distance. The beams rebound to sensitive detectors in the
aircraft where the resulting data are analyzed with a computer program that
ignores trees and other ground cover. A topographic map or an orthophoto is
created without the use of ground control. Precision is reported to be as fine as
10 cm (DeLoach and Leonard, 2000; Gillbeaut, 2003).
 
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