midterm Flashcards
Atmospheric Window
regions that are not blocked by the earth’s atmospheric gases, so we can see the surface from space
*H20, CO2 and O3 are the main gas species that absorb photons in the VIS-TIR and block our view
*energy is interacting with gases and particulates, so no atmospheric window is 100% clear
remote sensing
the non-contact recording of information from the electromagnetic spectrum by means of instruments on platforms such as spacecraft, and the analysis of the acquired information by means of visual and digital image processing (1)
advantages of remote sensing
-unobtrusive (passive)
-unbiased data collection
- non-single point data
-data collected on site (1)
disadvantages of remote sensing
- not a solution for everything
- human-introduced errors
- emit EM radiation (active)
- uncalibrated data over time
- expensive (1)
what can remote sensing measure?
- x,y geographic location
- topographic location
- vegetation health: chlorophyll content, water, % biomass, phytoplankton
- surface/sea temperature
- soil moisture & evaporation
- atmosphere: chemistry, temperature, water %, wind speed, precipitation, clouds
- other: snow/ice, volcanoes, earthquakes, wildfires, land use, ocean health (1)
what are the two types of remote sensing?
passive and active (1)
what is passive sensing?
detection of energy from natural illumination or emission
(ex. camera, visible near-infrared sensors, thermal infrared sensors) (1)
what is active sensing?
detection of energy reflected back to the sensor after providing the illumination
(ex. camera w flash, flashlight and your eye, radar, lasers) (1)
what are the five types of energy/matter interaction that can take place?
reflected, scattered, transmitted (refracted), absorbed, emitted (1)
energy is reflected. what does that tell you?
- energy returned from the surface with an angle reflection equal and opposite to angle of incidence
- caused by surfaces “smooth” relative to the incident wavelength (1)
energy is scattered. what does that tell you?
- deflection of energy in multiple directions
caused by surfaces “rough” relative to the incident wavelength (1)
energy is transmitted. what does that tell you?
-energy passes through the material
- a change in density (index of refraction) between two materials causes the velocity of the incident wave to change (1)
energy is absorbed. what does that tell you?
- energy is transformed (usually to longer wavelength heating) (1)
energy is emitted. what does this tell you?
- release of energy from the material (it is now the source) (1)
properties of EM waves
- waves have a constant velocity in a vacuum
- waves vary in wavelength and frequency by the following equation: v = c/λ
– c=speed of light, v= frequency, λ=wavelength
-E=hv
– E= energy of the wave, h=Planck constant, v=frequency - SMALLER WAVELENGTHS (HIGHER FREQUENCIES) HAVE HIGHER ENERGY
– ex. X-rays penetrate deeper and are more damaging to your body than radio waves (1)
what are the units of v in v=c/λ
Hz
(frequency)
what are the units of λ in v = c/λ
m
what are the units of E in E = hv?
Joules (J)
gamma rays
-produced by change in the energy state of the neutron/protons
-best for measuring variations in elements (light ones) (1)
x-rays
photons absorbed by the inner shell of electrons (1)
UV
-photons emitted/absorbed by the outer shell of electrons
-information on transition metals and chlorophyll
– Fe, Cu
(1)
VIS
photons emitted/absorbed by the outer shell of electrons (1)
NIR
photons emitted/absorbed by the outer shell of electrons (1)
SWIR
vibrational structure of certain materials
– OH- (hydroxide)
– CaCO3 (calcium carbonate) (1)