555
radiation for canopy modeling) and parameters (e.g., leaf angle distribution, leaf
area index) used to solve the radiative transfer equation in the shortwave, optical,
or longwave (i.e., thermal) domains.
Radiometric quality refers to the degree or accuracy of radiometric characterization, including resolution (see Radiometric resolution), typically determined by
radiometric calibration, providing an instrument response in absolute radiometric units (e.g., W m
−2
sr
−1
nm
−1
).
Radiometric resolution The smallest increment in spectral radiance that can be
detected by a sensor. This is determined by the dynamic range (the bit quantization level) and signal-to-noise ratio of the sensor.
Random forests A supervised machine learning algorithm that constructs many
decision trees and utilizes their outputs to get an accurate value of a variable or
class prediction based upon training data.
Random noise Noise component of a signal that does not contain information
about the property being measured. In remote sensing, random noise is often a
function of instrument electronics and temperature and is typically removed by
“dark correction” (subtracting the signal obtained when no external energy is
being measured, e.g., shutter is closed).
Random-walk process A stochastic process that describes a sequence of random
steps. The Brownian motion process used in models of evolution is an example
of a random walk. Note that a random walk of a species trait through time does
not necessarily mean that there is no selection: if the optimum value moves due
to many random factors (including randomly shifting forces of selection), and
the trait follows this closely, it is still approximated by a random walk.
Rate of evolution How fast trait changes accumulate over evolutionary time. In
the context of the evolution of quantitative traits, it typically refers to the pace of
evolution in a Brownian motion model.
Red edge The region of rapid change in a vegetation electromagnetic reflectance
spectrum that occurs at the transition from visible red to near infrared (between
650 and 800 nm) and indicates the boundary between chlorophyll absorption (in
the visible red) and vegetation scattering (in the near infrared).
Reflectance The ratio or percent of the radiance scattered backward from the
surface relative to the irradiance incident on the surface. Reflectance is a primary product of remote sensing optical data because it largely normalizes for
illumination, avoids the need for detailed radiometric calibration (e.g., calibration in energy units), and provides unique spectral shapes for different materials.
Contrast to absorptance and transmittance.
Reflectance signature the characteristic shape or pattern of reflectance across
wavelengths observed for a specific object (e.g., plant species) or condition.
Sometimes referred to as a spectral fingerprint.
Refractive index See index of refraction.
Regeneration Formation or regrowth of tissue, organ, organism or assemblage of
organisms (e.g., community or ecosystem).
Regional pool The set of species, populations, or organisms found within a
defined region that have the potential to disperse over time.
Glossary
radiation for canopy modeling) and parameters (e.g., leaf angle distribution, leaf
area index) used to solve the radiative transfer equation in the shortwave, optical,
or longwave (i.e., thermal) domains.
Radiometric quality refers to the degree or accuracy of radiometric characterization, including resolution (see Radiometric resolution), typically determined by
radiometric calibration, providing an instrument response in absolute radiometric units (e.g., W m
−2
sr
−1
nm
−1
).
Radiometric resolution The smallest increment in spectral radiance that can be
detected by a sensor. This is determined by the dynamic range (the bit quantization level) and signal-to-noise ratio of the sensor.
Random forests A supervised machine learning algorithm that constructs many
decision trees and utilizes their outputs to get an accurate value of a variable or
class prediction based upon training data.
Random noise Noise component of a signal that does not contain information
about the property being measured. In remote sensing, random noise is often a
function of instrument electronics and temperature and is typically removed by
“dark correction” (subtracting the signal obtained when no external energy is
being measured, e.g., shutter is closed).
Random-walk process A stochastic process that describes a sequence of random
steps. The Brownian motion process used in models of evolution is an example
of a random walk. Note that a random walk of a species trait through time does
not necessarily mean that there is no selection: if the optimum value moves due
to many random factors (including randomly shifting forces of selection), and
the trait follows this closely, it is still approximated by a random walk.
Rate of evolution How fast trait changes accumulate over evolutionary time. In
the context of the evolution of quantitative traits, it typically refers to the pace of
evolution in a Brownian motion model.
Red edge The region of rapid change in a vegetation electromagnetic reflectance
spectrum that occurs at the transition from visible red to near infrared (between
650 and 800 nm) and indicates the boundary between chlorophyll absorption (in
the visible red) and vegetation scattering (in the near infrared).
Reflectance The ratio or percent of the radiance scattered backward from the
surface relative to the irradiance incident on the surface. Reflectance is a primary product of remote sensing optical data because it largely normalizes for
illumination, avoids the need for detailed radiometric calibration (e.g., calibration in energy units), and provides unique spectral shapes for different materials.
Contrast to absorptance and transmittance.
Reflectance signature the characteristic shape or pattern of reflectance across
wavelengths observed for a specific object (e.g., plant species) or condition.
Sometimes referred to as a spectral fingerprint.
Refractive index See index of refraction.
Regeneration Formation or regrowth of tissue, organ, organism or assemblage of
organisms (e.g., community or ecosystem).
Regional pool The set of species, populations, or organisms found within a
defined region that have the potential to disperse over time.
Glossary