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Geographic Information Systems

Geographic Information Systems. GIS Data - Remote Sensing. Remote Sensing Definition. "I want to know how God created this world. I am not interested in this or that phenomenon, in the spectrum of this or that element. I want to know His thoughts; -the rest are details.“ Albert Einstein.

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Geographic Information Systems

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  1. Geographic Information Systems GIS Data - Remote Sensing

  2. Remote Sensing Definition "I want to know how God created this world. I am not interested in this or that phenomenon, in the spectrum of this or that element. I want to know His thoughts; -the rest are details.“ Albert Einstein

  3. Remote Sensing Definition .. • The technique of collecting information from a distance without physical touch • Remotely sensed data Aerial photography Digital satellite images Radar images etc.

  4. 2. Properties of EM Energy • EM travels at the speed of light 3x108m/sec • Wavelength l and Frequency n

  5. Properties .. • The type of energy is defined by its position in the EM spectrum in terms of wavelength, measured by mm • 1m = 1,000mm, 1mm = 1,000mm http://kr.blog.yahoo.com/bmw26z/2188

  6. Properties .. • Major divisions of EM spectrum • X-rays, UV, visible, infrared, microwave, TV http://csep10.phys.utk.edu/astr162/lect/light/spectrum.html

  7. Properties .. From http://rst.gsfc.nasa.gov/Intro/nicktutor_I-3.html • Atmospheric effects • Atmospheric absorption: H2O, CO2, O3

  8. Properties .. • Atmospheric windows Those wavelengths that are relatively easily transmitted through the atmosphere • The windows: UV, visible, near infrared, mid infrared, far infrared, microwave http://www.crisp.nus.edu.sg/~research/tutorial/atmoseff.htm#windows

  9. Properties .. • Atmospheric scattering The redirection of EM energy by particles suspended in the atmosphere or large molecules of atmospheric gases • Radiation of short wavelength is easier to be scattered http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/mch/sct.rxml

  10. Properties .. Reflection Absorption Transmission •  Responses of features on earth to EM energy Reflection (%), transmission (%), and absorption (%) Reflection + Transmission + Absorption = 100%

  11. Properties .. • Reflection - Light ray is redirected as it strikes a nontransparent surface

  12. Properties .. Reflection

  13. Properties .. • Transmission Radiation passes through a substance without significant attenuation • Transmittance (t):                   transmitted radiation            t =  ---------------------------                    incident radiation

  14. Properties Absorption and emission http://www.crisp.nus.edu.sg/~research/tutorial/infrared.htm

  15. 3. Major Sensor Systems • Aerial photography • Electro-Optical remote sensing • Microwave remote sensing

  16. 3 (1) Aerial Photography • Photographic cameras • Uses aerial cameras and film • Mounted on an aircraft • Produces aerial photographs

  17. 3 (2) Electro-Optical Remote Sensing • Electro-Optical scanners • Uses light-sensitive detectors • Mounted on spacecrafts or aircrafts • Generates digital images

  18. Buffalo, NY November 20, 2000 http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=4396

  19. Biloxi Coast–Before Hurricane Katrina, April 12, 2005 Biloxi Coast–After Hurricane Katrina, August 31, 2005. http://www.esri.com/news/pressroom/hurricanemaps.html

  20. 3 (3) Microwave Remote Sensing • Uses antennas as detectors • Passive microwave systems • Active microwave systems, RADAR

  21. http://rst.gsfc.nasa.gov/Sect8/Sect8_3.html http://www.erh.noaa.gov/buf/

  22. 4. Operation of Digital Remote Sensing • Moving mirror and pushbroom

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

  24. Operation .. • Sensors and detectors • Each sensor system contains a set of detectors, each set is sensitive to a certain range of wavelength (band) • Detectors of each band produce a digital image, which is a matrix consisting of rows and columns of pixels • The digital number of each pixel measures the intensity of energy received from the IFOV area on the ground • Images of several bands result in a composite image

  25. Operation .. Green Red Near Infrared NIR

  26. Operation • True and false color composite images

  27. 5. Types of Resolution • Spectral resolution • Radiometric resolution • Spatial resolution • Temporal resolution

  28. 5(1) Spectral Resolution • The dimension and the number of specific wavelength intervals in the EM spectrum to which a sensor is sensitive to, e.g. B, G, R, NIR bands Green Red Near Infrared NIR

  29. 5(2) Spatial Resolution • A measure of the smallest angular or linear separation between two objects that can be revolved by the sensor, 30m, 1m, 1km 10m 20m 40m 80m

  30. 5(3) Radiometric Resolution • The sensitivity of a detector to differences in signal strength as it records the radiant levels 1 bit 2 bit 4 bit 8 bit 2 levels 4 levels 16 levels 256 levels

  31. 5(4) Temporal Resolution • How often a given sensor obtains imagery of a particular area, e.g., 16 days, daily

  32. 6. Commonly Used Satellite Image Data • Moderate resolution land satellites Landsat SPOT Landsat 5, New York http://landsat.gsfc.nasa.gov/images/gallery.html

  33. 6. Commonly Used Satellite Image Data • High resolution land satellites • IKONOS • Orbview • GeoEye • QuickBird IKONOS images: Washington DC, Hoover Dam, Hollywood

  34. 6. Commonly Used Satellite Image Data .. • Meteorological satellites • AVHRR • EOS Sea surface temperature in hurricane alley. This false color composite image is made using data taken by AMSR-E on board EOS, May 2002. AVHRR

  35. 6. Commonly Used Satellite Image Data .. • Radar systems • RADARSET • LIDAR LIDAR Courtesy of EarthData Technologies RADARSET

  36. 6. Commonly Used Satellite Image Data .. • Digital aerial photographs • DOQQ LIDAR

  37. Readings • Chapter 8

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