Test 1 Flashcards
remote Sensing
acquiring information about a subject without coming into physical contact with it, through use of EMR
Electromagnetic waves
Require water and transmit energy
wavelength
the distance between wave crests
Frequency
number of crests passed in one second
What are the Visible wavelengths?
400-700 nm
What are the NIR wavelengths?
0.7-1.3 um
7-1.3 nm
What are the IR wavelengths?
700 nm-1mm
What wavelengths is SW?
2.5 um
What wavelength is LW?
2.5um-1mm
What happens are energy increases?
Frequency increases and wavelength becomes shorter
Source of passive energy?
Natural, like the sun
Source of active energy?
Sensor emits radiation
LIDAR and RADAR
What is spectral resolution?
the number, location, and bandwidths of EM spectrum and specific sensor is sensitive to
What is spatial resolution?
Relative to spectral response function; how close objects we can discriminate
what is multi-spectral?
10s of bands
what is hyper-spectral?
100s of bands
What is temporal?
How frequently we can get the data
What does temporal depend on?
Orbit, Field of View, and radiometric
What is swath?
The width of the coverage
higher the resolution the smaller the swath
What is radiometric?
How many different intensity levels can be discriminated by the remote sensor within a specific band?
What are the 3 ways to transfer energy from one place or object to another?
Conduction, Convection, Radiation
Radiant Flux
energy delivered to a surface in a unit of time
Irradiance
Radiation that strikes the surface
Exitance
rate at which radiation is emitted from a unit area
Radiance
radiant flux emitted, reflected, transmitted or received by a unit solid angle per unit projected area
Spectral radiance
Radiance of a surface per unit frequency or wavelength
Planck’s Law
describes the spectral density of EM radiation emitted by a black body in thermal equilibrium at a given temperature T
Stefan-Boltzmann Law
Defines the relationship between total emitted radiation (W) and temperature
Wien’s displacement law
Specifies the relationship between wavelength of radiation emitted and the temperature of a blackbody
what is scattering
redirection of EM energy by particles suspended in the atm or by large molecules of atm gasses
What does scattering depend on?
sizes of particles, abundance, wavelength of radiation, depth of atm
Reyleight scattering
Particle sizes are small compared to wavelength of em radiation
Dominant high in the atm
wavelength dependent
1/λ^4
Mie scattering
caused by larger atmospheric particles
occurs with particles that are 0.1 to 10 times the size of the wavelength
wavelength dependent
absorbs more in short wavelength
scatter more in longwave
Nonselective
wavelength is MUCH SMALLER than the particle size
is not wavelength dependent
absorption
occurs when the atm prevents transmissions of radiation or its energy through the atm
Refraction
bending of light rays at the contact area between two media that transmit light
Snells law
Reflectance
fraction of reflected flux to the incident flux
Absorbance
Fraction of absorbed flux to the incident flux
Transmittance
Fraction of transmitted flux to the incident flux
Reflections
a ray of light is redirected as it strikes a nontransparent surface
Spectral Reflectance
the surface is smooth, redirects all, or almost all, of the incident radiation in a single direction
Diffusive Reflectance
Surface is rough and energy is scattered in all directions
Lambertian surface
reflects light equally in all directions
Backwards scattering
Sun is behind the observer hiding most of the shadows
Reflection will be high
The bright spot in backwards scattering
hot spot
Nadir Observations
Reflectance will have medium values
0 incident angle
Forward Scattering
sun and viewer are in opposite directions
reflectance will have low values
Hot Spot
Occurs when the azimuth and zenith angle are equal to the sun
Anisotropy factor
The ratio of the radiance at a specific viewing geometry divided by the radiance at a nadir viewing geometry
Bidirectional reflectance distribution function
A mathematical description of the optical behavior of a surface with respect to angles of illumination and observation, given that is has been illuminated with a parallel beam of light at a specific azimuth and elevation
What is the dominating factor when measuring in visible for vegetation?
Leaf pigment, low reflectance causes green
What is the dominating factor when measuring in NIR for vegetation?
Multiple scattering within the cell structure
What is the dominating factor when measuring in SWIR for vegetation?
two absorption areas caused by water in the leaf
Reflectance in soil depends on?
Soil moisture, organic matter, soil texture, and iron oxide
How does increasing soil moisture content change reflectance?
Inverse relationship, as soil moisture goes up, reflectance goes down
How does increasing organic matter content change reflectance?
decreases reflectance
How does increasing soil texture change reflectance?
Portion of clay, silt, and ssand affects the ability to contain moisture and roughness
what particle size leads to high reflectance?
finer particles
Coarse particles have _________ reflectance?
lower
Does water absorb or reflect more?
more absorption
Describe the reflectance spectral plot for snow
High reflectance near 1 in the visible and decreases in the near IR with reflectance near to 0 from 1.5 um.
How does reflectance act with age?
it decreases with age, fresh snow has high reflectance than ice
Surface Albedo
the ratio of the radiant flux reflected from a unit surface area into the whole hemisphere to the incident radiant flux of hemisphere to the incident radiant flux or hemispherical angular extent
atmospheric correction
To perform quantitative analyses of RS data requires removal
of the atmospheric effects from the measurements
