Remote Sensing Data Acquisition

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Remote SensingData Acquisition
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1. Major Remote Sensing Systems
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Major Remote Sensing Systems

• Aerial photography
• Electro-Optical remote sensing
• Microwave remote sensing
• Close range remote sensing

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Aerial Photography

• Detector
• Process
• Vehicle
• Products aerial photographs

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(No Transcript)
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• http//nationalmap.gov/viewer.html
• http//www.abc.net.au/news/events/japan-quake-2011
  /beforeafter.htm

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Electro-Optical Remote Sensing

• Detector
• Process
• Vehicle
• Products Digital images

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Buffalo, NY November 20, 2000
http//earthobservatory.nasa.gov/Newsroom/NewImage
s/images.php3?img_id4396
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Biloxi CoastBefore Hurricane Katrina, April 12,
2005
Biloxi CoastAfter Hurricane Katrina, August 31,
2005.
http//www.esri.com/news/pressroom/hurricanemaps.h
tml
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Microwave Remote Sensing

• Uses antennas as detectors
• Passive microwave systems
• Active microwave systems, RADAR

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http//rst.gsfc.nasa.gov/Sect8/Sect8_3.html
http//www.erh.noaa.gov/buf/
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Close Range Remote Sensing

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• Visual interpretation vs. digital image
  processing

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2. Resolutions

• Spectral resolution
• Radiometric resolution
• Spatial resolution
• Temporal resolution

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Spectral Resolutions

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Spectral Resolutions

• The dimension and the number of specific
  wavelength intervals in the EM spectrum to which
  a sensor is sensitive, e.g. B, G, R NIR bands

Green
Red
Near Infrared
NIR
http//rst.gsfc.nasa.gov/Intro/Part2_17.html
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Radiometric Resolution

• The sensitivity of a detector to differences in
  signal strength as it records the radiant flux
  reflected or emitted from the terrain

8 bit 4 bit 2 bit 1 bit
256 levels 16 levels 4 levels
2 levels
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Spatial Resolution

• A measure of the smallest angular or linear
  separation between two objects that can be
  resolved by the sensor, 30m, 1m, 1km

10m 20m 40m 80m
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Temporal Resolution

• How often a given sensor obtains imagery of a
  particular area, e.g., 16 days, daily

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Pixels and IFOV

• Pixel - picture element
• IFOV - Instantaneous Field of View the ground
  area viewed by the sensor at a given instant

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3. Color Theory

• Additive primaries
• Subtractive primaries

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Additive Primaries

• blue, green, and red  superimposing blue, green,
  and red light
• blue  green red white      green red 
  yellow      green blue cyan      red  
  blue magenta

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Color Theory

• Yellow, magenta, and cyan are complements of
  blue, green, and red, respectively
•  Various combinations of the three primaries
  produce different colors

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Subtractive Primaries

• yellow, magenta, and cyan each absorbs its
  complementary color from white light          
  yellow  white - blue           magenta white
  - green           cyan  white - red

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Subtractive Primaries

• Superimposing yellow, magenta, and cyan dye
        yellow  magenta cyan black       
  yellow  magenta red        yellow  cyan 
  green        magenta cyan  blue

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True and False Color Images
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True and False Color Images
http//www.crisp.nus.edu.sg/research/tutorial/opt
_int.htm
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• Readings Chpt 2.7

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4. Introduction of Satellite Systems

•  Land observation satellite systems
•         vehicles - spacecraft         devices
  - electro-optical sensors         images -
  digital images         target - earth resources

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Satellite Systems

•  Advantages vs. aerial photography
• provide a synoptic view systematic,
  repetitive coverage multiple spectral
  information digital format for quantitative
  analysis less expensive

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History of Satellite Systems

• Landsat (Land Satellite) system  - launched in
  1972  - first satellite for observation of the
  earth's land
• areas  - important in earth resources
  studies and a
• model for later satellite systems

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History of Satellite Systems

• Early Landsat (1,2,3) was named Earth Resources
  Technology Satellite (ERTS) and designated by a
  letter, i.e. A,B,C, renamed later as Landsat 1,
  2, 3
• Early Landsat applied spectrums used in aerial
  photography but at a satellite altitude
• Early Landsat carried Return Beam Vidicon (RBV)
  and Multispectral Scanner (MSS) sensor systems
• New generation of Landsat (4,5,7) carries MSS
  and Thematic Mapper (TM) and other more
  sophisticated sensor systems

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Satellite Orbits

• Geosynchronous orbits
• Sun-synchronous orbits
• Inclination
• Ascending and descending nodes   

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Geosynchronous Orbits

• Revolve at an angular rate that matches the
  earth's rotation
• Weather satellites, communication satellites
• Views the full range of variation of solar
  illumination

http//www.crisp.nus.edu.sg/research/tutorial/spa
cebrn.htm
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Sun-Synchroneous Orbits

• Maintain a constant angular relationship with
  the solar beam, the satellite will always pass
  overhead at the same local time for similar
  illumination and shadowing conditions

http//www.crisp.nus.edu.sg/research/tutorial/spa
cebrn.htm
http//www.youtube.com/watch?vLttI1IofXRI
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Satellite Orbits

• Inclination the angle between the orbital plane
  and the equatorial plane
• Coverage of the earth's surface

http//www.atmos.umd.edu/owen/CHPI/IMAGES/orbitss
.html
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Satellite Orbits

• Descending node  - the point the satellite
  crosses equator on southward track
•  Ascending node  - the point the satellite
  crosses equator on northward track

http//www.ccrs.nrcan.gc.ca/ccrs/learn/tutorials/f
undam/chapter2/chapter2_2_e.html
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Satellite Orbits

• Most satellites cross over the equator at about
  930am, an optimal time with respect to sun angle
  and cloud cover
•  

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Readings

• Chapter 6