Spectral Unmixing Applied to Desert Soils for the - Naval ...

II. THE PHYSICS BEHIND REMOTE SENSING
A. REMOTE SENSING
The term remote sensing refers to the ability to conduct measurements and
interpretation of events without being present at the location being studied (Goetz and
Rowan, 1981). Remote Sensing instruments make measurements by utilizing solutions to
the wave equation:
where:
is the wave amplitude,
is the angular frequency,
is the phase,
is the wave vector in some propagation medium (Elachi and Van Zyl, 2006).
Remote sensing is useful for a variety of applications including mineral
distribution mapping, geologic formation mapping, pollution studies, and geo-ecological
relationships (Gathercole, 1987). Use of remote systems such as satellite borne sensors is
possible because when light interacts with materials on the surface of the earth it is
scattered, transmitted, reflected and absorbed by those materials (Figure 1). Some of that
light is then directed in the form of photons toward an observing sensor and measured as
radiance (Clark, 1999). The radiance measured by the sensor is calculated using the
radiance equation (2) below after Gao and Goetz (1990).
where:
is the radiance observed by the sensor,
3
(1)
(2)