1.3.2. Hyperspectral Imagery
Hyperspectral imagery is acquired using a sensor that collects
many tens to even hundreds of bands of electromagnetic energy. This imagery is
distinguished from multispectral imagery not only by the number of bands, but
also by the width of each band. Multispectral imagery senses a limited number
of rather broad wavelength ranges that are often not continuous along the
electromagnetic spectrum. Hyperspectral imagery, on the other hand, senses many
very narrow wavelength ranges (e.g., 10 microns in width) continuously along
the electromagnetic spectrum (Palace et al, 2008).
1.3.3. Digital Camera Imagery
Most digital camera imagery is collected as a natural color
image (blue, green, and red) or as a color infrared image (green, red, and near
infrared). Recently, more projects are acquiring all four wavelengths of
imagery (blue, green, red, and near infrared). The spatial resolution of
digital camera imagery is very high with 1-2 meter pixels being very common and
some imagery having pixels as small as 15 cm.
1.3.4. Other Imagery
There are other sources of digital remotely sensed imagery
that have not been pre-sented in this paper. These sources include RADAR and
LiDAR. Both these sources of imagery are important, but beyond the scope of
this paper. RADAR imagery has been available for many years. However, only
recently has the multifrequency component of RADAR imagery become available
(collecting frequencies of imagery simultaneously and not just multiple
polarizations) that significantly improves the ability to create thematic maps
from this imagery. LiDAR has revolutionized the collection of elevation data
(Maidment et al., 2007) and is a valuable source of information that can be
used in creating thematic maps (Im et al., 2008). In the last few years, these
data have become commercially available and are being used as a vital part of
many mapping projects.
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