Properties objects to the light. There are two

Properties of satellite images

Remote sensing includes the set of sensors and
data processing procedures that are deployed to develop information concerning
different properties of the Earths’ surface (i.e. the land, atmosphere, and
oceans) which can be achieved with no direct physical contact. Information is
obtained from capturing the reflected waves from the earth surface, and its
difference as a function of wavelength, phase, location, and time. A variety of
sensors are generally deployed both passive (i.e. which depends on reflected
solar radiation or emitted radiation) and active (i.e. which generates its own
source of Electromagnetic (EM) waves).These sensors work all over the EM range
from visible to microwave wavelengths. There are different platforms on which
these sensors are attached such as earth-orbiting satellites, aircraft are by
far the most common. Normally, remote sensing images are classified according
to four different characteristics based on the type of sensors technology. The
first characteristic is the spatial resolution where the higher is the resolution
the clearer objects on earth appears in the image (the known highest resolution
is approximately few centimeters while the lowest can reach 9 kilometers). The
lower is the resolution the more area is captured. The second characteristic of
the remote sensing images is the spectral resolution. It describes the capacity
of the sensors to differentiate between wavelengths in the EM spectrum. The
finer the resolution more bands are recorded which means that it is possible to
obtain more details about the reaction of sensed objects to the light. There
are two technologies hyperspectral and multispectral where the first can have a
spectral resolution of 1 nm with hundreds of bands compared to rougher spectral
resolution for the multispectral that can reach 100 nm with few bands. The
third property is the temporal one which defines the period of time needed by a
satellite to revisit the same spot on earth. The less time needed to revisit a
specific area the higher is the temporal resolution. The fourth and last
characteristic is the radiometric which specifies how well the differences in
brightness in an image can be perceived. This is measured through the number of
the levels of the gray value. The maximum value related to radiometric
resolution is defined by the number of bits where eight bits representation has
256 gray values, a sixteen bits representation has 65,536 gray values. The
finer or the higher the radiometric property is the better is the recorded reflected
waves, but the volume of measured data will be larger.