Geography Reference
In-Depth Information
graphic film (called an “emulsion”) or by using digital devices built and cali-
brated to detect this EMR spectrum.
The data collected and images made with Landsat, SPOT, and similar sens-
ing technologies are known as multispectrum because of they include differ-
ent bands. The variability of multispectrum remote sensors opens up a vast
number of application possibilities.
This type of sensor technology collects more than 16 bands simultaneously.
For example, the Hyperion satellite collects 220 bands from blue to
shortwave infrared in equal steps (from 0.4 to 2.5 µm) with a 30-m spatial
resolution. Flying in formation with Landsat 7, images from Hyperion can
be used easily with Landsat 7 images and data.
Radar is an important remote sensing sensor type. Its ability to penetrate
through cloud cover and into the ground make it very useful for applications
in areas with frequent cloud cover and for geological work.
Laser (LiDAR)
Not used on satellites, but on planes, helicopters, and from the ground, LI ght
D etection A nd R anging (LiDAR) uses a laser to generate light pulses, the same
way radar uses radio waves. LiDAR is highly accurate and cost-effective for col-
lecting elevation data. Because of LiDAR's speed, hand-held units have been
introduced to quickly scan an area—for example, a crime or accident scene.
Images acquired by satellites have been used to produce local, regional,
national, and global composite multispectral mosaics. They have been used
in countless applications including monitoring timber losses in the U.S.
Pacific Northwest, establishing urban growth, and measuring forest cover.
Remote sensing images have also been used in military operations, to locate
mineral deposits, to monitor strip mining, and to assess natural changes due
to fires and insect infestations.
Data Collection in General
Thinking about remote sensing in a most general sense, we can easily distin-
guish types of data collection by the platform and by sensor technology. If
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