Ground Truth Studies Teacher Handbook - Aspen Global Change ...

Remote Sensing & Ground Truth Primer (continued)
Sensors
In the process of remote sensing, information about our environment is conveyed by electromagnetic energy and received
and recorded by sensors. Most modern technological sensors have counterparts that occur in nature. For example, the
photographic camera and the human eye both sense visible light; the microphone and the ear pick up sound waves; smoke
alarms and noses both sense molecular dispersions we call odors. The sensors used in remote sensing are primarily
sensitive to UV, visible, infrared, and microwave wavelengths; they sense and record data in these spectral bands. These
data are then generally converted to image form for print or computer viewing and enhancement. Radar senses in the
microwave region of the spectrum; the Landsat thematic mapper sensor senses in the visible and near to mid infrared.
Platforms
The physical platforms that carry sensors affect their capabilities and provide their perspectives. Platforms for remote
sensing can be on land or in water, air or space. Aircraft platforms are typically flown at altitudes between 3,000 and
21,000 meters (figure 10). The data they deliver are either digital or photographic. The information we receive from
space is generally digital and comes from NOAA weather satellites like GOES, earth resources satellites like Landsat and
SPOT, and from manned missions such as the Space Shuttle. In the near future, information will also come from the
SeaStar ocean color satellite, as well as the Earth Observing System (EOS) satellites, which will make a wide range of
environmental measurements.
Landsat
700 km
Landsat
700 km
High Altitude Aircraft
High
up
Altitude
to 12 km
Aircraft
up to 20 km
Low Altitude Aircraft Aircraft
up to 10 6 km km
185 km
18 km
9 km
Figure 10: Altitudes of three commonly used remote sensing platforms and the approximate width of their images.
© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES
32