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Remote Sensing Flashcards

kalifimoon Remote Sensing Undergraduate English 62 cards

What important implication does c = λv have?

Cards in this deck (62)

  1. 1What is electromagnetic radiation?Energy traveling from the sun to earth in the form of periodic disturbances of the electric and magnetic fields at the speed of 3 x 10^8
  2. 2How does the Aurora Borealis work?Energy from the sun is pushed north (Borealis) and south (Australis) by the magnetic field of the earth produced by its rotation
  3. 3What is the fundamental unit of energy?Photon
  4. 4How are photons produced?When an object is thermally excited
    When an object is engaged in nuclear fission/fusion
  5. 5Broad definition of remote sensingGather information about the physical world by measuring radiation, particles, and fields associated with the objects beyond the sensor's immediate vicinity
  6. 6Specific definition of remote sensingTechnology for sampling electromagnetic radiation, to interpret non-immediate geospatial data from which to extract information on objects from earth's land, water and atmsophere
  7. 7Closest measurement and farthest measurement using remote sensing?10 centimeters, or 1 km
  8. 8What are the principal applications of remote sensing?1. Vegetation (biomass, habitat, disturbance)
    2. Geological (landform, faults, igneous changes)
    3. Water/Ocean (sea ice, turbidity, wave patterns)
    4. Forestry (harvest, inventory, clearcutting/regeneration)
  9. 9When you see a photon coming from an object, where is it coming from?It is coming from warmth or it is reflected
  10. 10What is a wavelength?λ
    The distance between two peaks of wave
  11. 11What is frequency?v
    the number of peaks that will pass through one point in one second
  12. 12How do you relate frequency and wavelength?c = λv
    (speed of light)=(wavelength)*(frequency)
  13. 13With respect to the speed of light - if a wavelength gets longer, what happens to the frequencyas wavelength increases (gets longer), the lower the frequency.
  14. 14What is a quanta?a discrete quantity of energy proportional in magnitude to the frequency of the radiation it represents.
  15. 15What important implication does c = λv have?The longer the wavelength, the lower the frequency. The lower the frequency, the lower the quanta. There fore long wavelengths emit low quanta, meaning it takes larger areas (greater resolution) to sense long wavelength energy.What important implication does c = λv have?
  16. 16Why can't we sense longer waves in small areas?Because, given the equation c = λv, the longer the wavelength, the lower the frequency, the lower the frequency, the lower the energy, the more difficult it is to sense in small areas. Need to broaden resolution
  17. 17How is the relationship between quanta energy and wavelength characterized?Q = hν
    (Quanta)=(Plank's constant)*(frequency)
  18. 18Define Gamma and x-RaysMeasurement: Less than 10 Angstroms
    Characteristic: Earth's atmosphere blocks this radiation almost completely
  19. 19Define Ultraviolet1-400 nanometers
    Mostly blocked by the atmosphere, absorbed by ozone, except from 300-400nm
  20. 20Define Visible Radiation400-700 nanometers
    Earth's atmosphere mostly transparent to this radiation
  21. 21Define Reflective (near) Infrared700-3000nm: .7-3 microns
    also called photographic IR
    High absorption by water vapor in the atmosphere
  22. 22Define Thermal (far) Infrared3-10,000 microns
    Terrestrially derived, absorption by water vapor and CO2 in the atmosphere
  23. 23Define Microwaves0.1 to 30 cm
    wavelengths used in radar
  24. 24Define Radio WavesAnything greater than 30 cm
    Classified RADARs, transparent to atmosphere
  25. 25What are the conversion rates of all units with regard to meters?1km=10^3
    1cm=10^-2
    1mm=10^-3
    1 micron=10^-6
    1 nanometer=10^-9
    1 Angstrom=10^-10
  26. 26What is a Blackbody?A theoretical construct used to estimate the amount of radiation coming from the sun based on temperature estimates.
    The temperature of the body will tell us the wavelength of the photons coming from it
  27. 27What is the significance of blackbodies?Heat means object emits more intense radiation at higher frequencies.
    Shift peak radiation intensity to shorter wavelengths as temperature increases, and covers more of the spectrum
  28. 28Define Solar IrradianceSolar irradiation (also called insolation) arrives at Earth-at wavelengths which determined by the temperature of the sun (peaking near 5600 °C).
  29. 29Atmosphere Interactions: what can happen to photons going through the atmosphere?1. Scattered: photon hits a molecule but is not absorbed, simply changes direction
    2. Absorbed: hit an atmosphere molecule (water vapor -absorbing 3xmore, CO2, O3), takes the energy of the photon, release energy as heat
    3. Transmitted: photons that pass through the atmosphere without being changed
  30. 30What are the different types of scattering?Rayleigh: object size < wavelength (e.g. gas molecule). longer the wavelength less scattering (^4)
    Mie: object size = 0.1-10x wavelength size (smoke, dust)
    Non-selective: object size > wavelength (clouds) - most problematic
  31. 31What is a consequence of the Rayleigh principal?Images are clearer with longer frequency wavelengths, because of less scattering
  32. 32Explain the different types of Surface Interaction (reflectance)1. Transmitted: penetrates surface materials (translucent: water, glass, some vegetation)
    2. Absorbed: photons are being absorbed through molecular reactions (pigment)
    3. Reflected: radiation reflects and scatters away at various angles depends on surface roughness and angle of incidence of rays.
  33. 33What is the Incidence Angle?The angle at which the energy strikes an object
  34. 34Difference between Multispectral and Hypersectral?Multispectral: usually landscape level studies, 185 km swath width, 30 m spatial resolution, captures more energy in less detail
    Hyper spectral: Finer scale studies, 2km swaths, 2 m spatial resolution, captures less energy in more detail
  35. 35Describe GOES SensorGeostationary Operational Environmental Satellites: Visible and Thermal Bands, low spatial resolution (1x1k vis, 4x4 k therm), hemispheric coverage, but is geosynchronous (1 spot), data dating back to 1968, best for analyzing local patterns over time, like weather forecasts, storm tracking, cloud cover
  36. 36Describe TIROS/NOAA AVHRRAdvanced Very High Resolution Radiometer: Old data (1978) to present, wide swatch, low resolution (1km), global coverage, twice a day, Visible and NIR, used for sea surface temp, change in vegetation
  37. 37Describe NASA Earth Observing System (EOS)EOS: data from 1999, used to measure earth's land, biosphere, atmosphere and oceans
  38. 38Describe MODISModerate Resolution Imaging Spectroradiometer: Measurement of global , sun synchronous, spatial resolution between 10-100m, spectral bands between 1-10, launched in 1972
  39. 39Describe Landsat MSSMultispectral Scanner: 1972-1982: 4 bands, Visible (Green Red?) and NIR, used for old data, vegetation cover, surface features, water turbidity
  40. 40Describe Landsat TMLandsat Thematic Mapper: Higher resolution (30x30) 7 bands, most parts of spectrum visible, NIR, NIR, Thermal, old data to present (1984
  41. 41Describe Landsat ETMEnhanced Thematic Mapper: 8 bands, all spectrum, panchromatic, newer data 1999-present
  42. 42Describe SPOTSystème Probatoire d"observation de la Terre: very high resolution 20-2.5 m, 1998-present, coverage in 26 days, 4 bands (visible, NIR, SWIR, Pan)
    Vegetation is more coarse: 1.15, worse than landsat, only 4 bands, 1998-present
  43. 43Describe kinds of High Resolution SatellitesIKONOS: 1 m
    Quickbird: 0.7 m
    But costly and data do not date back
  44. 44What are the different spectral signatures when it comes to reflectance?Perfect Specular (isotropy) (draw graph - angle of incidence vs angle of reflectance)
    Near Perfect specular (draw graph) i.e. snow
    Perfect Diffuse (anisotropy, lambertian): (draw graph)
    Near-Perfect Diffuse: draw graph (trees)
  45. 45Why is Lambersion Important for Remote sensing?Because the wavelength will be reflected and caught by the sensor no matter the angle of incidence
  46. 46What is a Spectral Signature?The % of radiation vs wavelength
  47. 47Why does vegetation render different spectral signatures?Different species of leaves have different pigments, that absorb and reflect different wavelengths
  48. 48Name the 4 most dominant pigments, what is the most dominant pigment in a leaf?Chlorophyll (most dominant), Carotenoids and Flavonoids, Carotenoids, and Anthocynannis and Carotenoids
  49. 49What components of a leaf let us know the state of the leaf?Palisade Parenchyma: top part of the leaf, contains chlorophyll who's pigment determines the absorption of visible light (at 0.43-0.66um)
    Spongy Parenchyma Mesophyll: lower part of the leaf that upholds the structure of the leaf, when abundant (in growing season), NIR bounces around the spongy mesophyll reflects
  50. 50What is the optimal absorption window for healthy leafs?0.43-0.66 microns
  51. 51How does water play a role in reflection?Water has high transmissions rates, so the more water, the less reflectance
  52. 52Draw overlapping curves for a health and unhealthy leafDraw overlapping curves for a health and unhealthy leaf
  53. 53What is NDVI?Normalized Different Vegetation Index is an easier way to calculate the difference in reflection of various wavelengths that signal the state of a leaf: NIR-Red/NIR+Red
  54. 54What are the 4 types of Resolution?Spatial, Radiometric, Spectral, and Temporal
  55. 55Describe Spatial ResolutionPhotons appear to a sensor at an angle called Instantaneous Field of View. This flows to the sensor in a conical shape. These are captured by a pixel, the square shape that fits around each circle at the base of the cone. Pixels can be large (low), and small (high). Pixel=IFOV*sensor altitude
  56. 56With regard to Spatial resolution, What does your image depend on?1. What your IFOV is
    2. Contrast (tennis courts)
    Clarity of atmosphere
  57. 57Describe Radiometric ResolutionThe number of different levels of brightness a sensor can record (2 bit, 4 bit, 8 bit). More levels more detail
  58. 58Describe Spectral Resolution# of bands, location on the electromagnetic spectrum, and band width
    1. Panchromatic: 1 band, Vis and NIR, fat band
    2. Multispectral: more than 1 band, Vis, NIR, MIR, etc..., depends on sat, varying sizes
    3. Hyper-Spectral: multiple bands, covering all spectrum, contiguous narrow bands
  59. 59Describe the importance of signal to noise ratio (SNR)The greater the signal the lower the noise (panchromatic, lower noise, hyper spectral narrow bands, more spectrum detail, but more noise per band)
    SNR must be high
  60. 60What are the different Sensor Types?Cross Track Sensor: back and forth sweep, scans each cell one by one, IFOV determines pixel size, built up by movement over orbital track and scan across track. Error: when can't transmit info because too bright, too dark: horizontal lines
    Push broom (along track) Sensor: linear array of sensors picking up each cell along the track
    linear: every pixel length, area: swatch length
  61. 61Describe Temporal ResolutionHow often a sensor can record imagery of the same location (once a day)
    Or
    Time interval associated with observations (how many instances over the years)
    Depends on orbital patterns, swath width, pointing ability.
    Low: much time passed (decade)
    High: little time passed (day)
  62. 62Describe the types of orbitsGeo-stationary: orbit speed matched to rotation of the earth, location static, altitude: 36,000km (uses: weather, telephone, television)
    Sun-synchronous: crosses close to the poles, satellite crosses equator same time every day. example polar orbiting, 600-1000km, global coverage

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Undergraduate Remote Sensing Flashcards on Remote Sensing Flashcards, created by kalifimoon on 17/02/2016.
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