Karteikarten
Remote Sensing Flashcards
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- 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
- 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
- 3What is the fundamental unit of energy?Photon
- 4How are photons produced?When an object is thermally excited
When an object is engaged in nuclear fission/fusion - 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
- 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
- 7Closest measurement and farthest measurement using remote sensing?10 centimeters, or 1 km
- 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) - 9When you see a photon coming from an object, where is it coming from?It is coming from warmth or it is reflected
- 10What is a wavelength?λ
The distance between two peaks of wave - 11What is frequency?v
the number of peaks that will pass through one point in one second - 12How do you relate frequency and wavelength?c = λv
(speed of light)=(wavelength)*(frequency) - 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.
- 14What is a quanta?a discrete quantity of energy proportional in magnitude to the frequency of the radiation it represents.
- 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.
- 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
- 17How is the relationship between quanta energy and wavelength characterized?Q = hν
(Quanta)=(Plank's constant)*(frequency) - 18Define Gamma and x-RaysMeasurement: Less than 10 Angstroms
Characteristic: Earth's atmosphere blocks this radiation almost completely - 19Define Ultraviolet1-400 nanometers
Mostly blocked by the atmosphere, absorbed by ozone, except from 300-400nm - 20Define Visible Radiation400-700 nanometers
Earth's atmosphere mostly transparent to this radiation - 21Define Reflective (near) Infrared700-3000nm: .7-3 microns
also called photographic IR
High absorption by water vapor in the atmosphere - 22Define Thermal (far) Infrared3-10,000 microns
Terrestrially derived, absorption by water vapor and CO2 in the atmosphere - 23Define Microwaves0.1 to 30 cm
wavelengths used in radar - 24Define Radio WavesAnything greater than 30 cm
Classified RADARs, transparent to atmosphere - 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 - 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 - 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 - 28Define Solar IrradianceSolar irradiation (also called insolation) arrives at Earth-at wavelengths which determined by the temperature of the sun (peaking near 5600 °C).
- 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 - 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 - 31What is a consequence of the Rayleigh principal?Images are clearer with longer frequency wavelengths, because of less scattering
- 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. - 33What is the Incidence Angle?The angle at which the energy strikes an object
- 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 - 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
- 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
- 37Describe NASA Earth Observing System (EOS)EOS: data from 1999, used to measure earth's land, biosphere, atmosphere and oceans
- 38Describe MODISModerate Resolution Imaging Spectroradiometer: Measurement of global , sun synchronous, spatial resolution between 10-100m, spectral bands between 1-10, launched in 1972
- 39Describe Landsat MSSMultispectral Scanner: 1972-1982: 4 bands, Visible (Green Red?) and NIR, used for old data, vegetation cover, surface features, water turbidity
- 40Describe Landsat TMLandsat Thematic Mapper: Higher resolution (30x30) 7 bands, most parts of spectrum visible, NIR, NIR, Thermal, old data to present (1984
- 41Describe Landsat ETMEnhanced Thematic Mapper: 8 bands, all spectrum, panchromatic, newer data 1999-present
- 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 - 43Describe kinds of High Resolution SatellitesIKONOS: 1 m
Quickbird: 0.7 m
But costly and data do not date back - 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) - 45Why is Lambersion Important for Remote sensing?Because the wavelength will be reflected and caught by the sensor no matter the angle of incidence
- 46What is a Spectral Signature?The % of radiation vs wavelength
- 47Why does vegetation render different spectral signatures?Different species of leaves have different pigments, that absorb and reflect different wavelengths
- 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
- 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 - 50What is the optimal absorption window for healthy leafs?0.43-0.66 microns
- 51How does water play a role in reflection?Water has high transmissions rates, so the more water, the less reflectance
- 52Draw overlapping curves for a health and unhealthy leaf
- 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
- 54What are the 4 types of Resolution?Spatial, Radiometric, Spectral, and Temporal
- 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
- 56With regard to Spatial resolution, What does your image depend on?1. What your IFOV is
2. Contrast (tennis courts)
Clarity of atmosphere - 57Describe Radiometric ResolutionThe number of different levels of brightness a sensor can record (2 bit, 4 bit, 8 bit). More levels more detail
- 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 - 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 - 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 - 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) - 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 Karteikarten am Remote Sensing Flashcards, erstellt von kalifimoon am 17/02/2016.
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