TheImprovement ofTropical and Subtropical Rangelands

REGIONAL RESOUROE AS8mJSMENT 85
60
Dry bare soli
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Vegetation
(green)
o
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
FIGURE 4-2
Wavelength (micrometers)
Spectral character.tica of different earth materiala.
as size, shape, and even texture are noted. Other important characteristics
of remote sensing systems have to do with system resolution,
or its -sharpn"'- in several dimensiona--spatial, temporal,
and spectral.
SpatJal I'tlIOlutlan broadly describes the quality of the system
that determines the smallest feature that might be detected. Thus,
spatial resolution influences the ability to detect features baaed upon
geometric characteristics. For example, to determine tree densities
in savannah vegetation, relatively high-resolution images would be
required to see individual trees, while simply to map the boundary
between forest and savanna,low-reeolution images might be preferred
to enhance differences in total tree cover rather than the location of
individual trees.
Temporal ntOlutlan deecribes how often a system acquires images
for a single point. Although not usually a consideration for aerial
photography, temporal reeolution is an important characteristic of
satellite systems becaue they operate continuously. For example,
mapping forests in a large area and also distinguiahing between evergreen
and deciduous types would require a system that acquires
images frequently enough to usure at least one cloud-free image from
both summer and winter.
Spectrall'elOlutlan deecribes the location and width of the parts
(banda) ofthe spectrum in which the system records. Earth materials
reflect and emit electromagnetic radiation in different ways. To
improve the ability to discriminate features, it can be useful to employ