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Remote Sensing Image Acquisition

Remote Sensing Image Acquisition. Supplement to Lecture 1 material prepared by R. Lathrop 9/99 updated 8/03 includes slides previously prepared by S. Madry and C. Colvard Readings: ERDAS Field Guide 5th Ed. Ch 1, 3:56-82. Digital Image Acquisition.

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Remote Sensing Image Acquisition

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  1. Remote Sensing Image Acquisition Supplement to Lecture 1 material prepared by R. Lathrop 9/99 updated 8/03 includes slides previously prepared by S. Madry and C. Colvard Readings: ERDAS Field Guide 5th Ed. Ch 1, 3:56-82

  2. Digital Image Acquisition • Digitization of analog aerial photography, can be very useful for historical studies and/or for high spatial resolution needs • Direct acquisition using some form of digital imaging sensor

  3. Early attempts • Kite system acquired aerial photos of the great San Francisco earthquake and fire • Pigeon cameras • The development of aircraft • World Wars I and II

  4. Aerial Cameras Keystone’s Wild RC-10 mapping camera A large format oblique camera

  5. Aerial photos • Black & White - single panchromatic layer • Color: 3 layers B-G-R • Color IR: 3 layers G-R-NIR

  6. USGS Aerial Photo Products Aerial Products Description National Aerial Photography Program (NAPP) Recent,high-quality aerial photos covering the conterminous U.S. on five- to seven-year cycles (1987 - present). National High Altitude Photography (NHAP) High-altitude aerial photos for the conterminous U.S. (1980 - 1989). Digital Orthophoto Quadrangles (DOQs) Digital images of aerial photos which combine the image characteristics of the photo with the georeferenced qualities of a map (1987 - present). Space Acquired Photography Photos taken from the International Space Station (ISS), Shuttle, Skylab, Gemini, and Apollo missions (1965 - present). For more info: http://edc.usgs.gov/products/aerial.html

  7. Analog Image Digitization • Scanning micro-densitometer • Linear array charge-coupled device e.g., flat-bed scanners • Area array charge-coupled device e.g., digital camera

  8. Remote Sensing Systems - Instrumentation • Radiometer - electro-optical instrument measuring radiant flux (energy) • Spectroradiometer - instrument that measures radiant flux as a function of wavelength - often as a continuous spectra • Multispectral scanner - imaging spectro-radiometer measuring radiant flux in specific spectral wavebands

  9. Major Elements of electro-optical scanners • Optical system: lenses, mirrors, apertures, modulators & dispersion devices • Detectors: provide an electrical signal proportional to the irradiance on its active surface, generally some type of semiconductors • Signal Processor: performing specified functions on the electrical signal to provide the desired output data

  10. Electro-optical scanners • Elements sensitive to electro magnetic energy (EME) of certain wavelengths focus energy onto a sensor plane. A prism is used to divide the energy into specific wavelengths. The CCD’s are stimulated and produce an electrical signal equal to the energy focused upon it. These data are recorded. • Data are converted from an analog electrical signal to a digital number

  11. 3 different scanner designs Single detector CCD-Scan Mirror TM Pushbroom scanner SPOT Two dimensional Staring Array Space Imaging Original Current Future

  12. Important imaging parameters • The Instantaneous Field of View (IFOV) subtends an area on the terrain called a Ground Resolution Cell (GRC) • The Angular Field of View determines the width of the Ground Swath • The Dwell Time, the time required for the detector IFOV to sweep across the GRC

  13. Airborne Remote Sensing Aircraft ScannersDigital imagery acquired from several multispectral scanners on board NASA ER-2, NASA C-130B, and NASA Learjet aircrafts (1982 - 1995). For more info: http://edcdaac.usgs.gov/airborne/air_scan.html Digital Cameras increasingly aerial imagery is being acquired through digital camera framing systems that can collect multispectral (VIS-NIR) imagery and be quickly corrected through GPS-based navigational systems to produce digital orthophotographic imagery in near-real time

  14. Remote Sensing Satellites in Space: How do they get there? http://visibleearth.nasa.gov/cgi-bin/viewrecord?492

  15. MODIS Terra Launches http://visibleearth.nasa.gov/cgi-bin/viewrecord?135

  16. Types of satellite orbits • Geostationary Polar 700-900 km 35,800 km

  17. Polar Orbitting Satellite http://visibleearth.nasa.gov/cgi-bin/viewrecord?134

  18. Geostationary vs. polar orbiting sensors Geostationary sensors orbit with the earth continually viewing the same hemispheric area Polar orbiters, continually view new areas of the earth as the planet rotates underneath the sensor. Keeps the same general solar time as it cross the equator on each orbit - called sun synchronous Polar orbit

  19. Many different systems - which to choose?

  20. AVHRR-Advanced Very High Resolution Radiometer • Polar orbit, coarse spatial resolution: 1 and 4 km cells, broad 2400 km ground swath width • 2 operational now-1 day and 1 night pass for each

  21. AVHRR • Thermal AVHRR provides water temperature data • 3 bands in TIR Gulf Stream

  22. Remote Sensing of the Earth: Clues to a Living Planet • Scientists at the NASA Goddard Space Flight Center have used the AVHRR to create maps of vegetation greenness for the entire globe • The NASA scientists have combined numbers of satellite images to create a composite picture of the earth at approximately biweekly intervals over a number of years For more info and images, go to: http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/BRS_SRVR/avhrrbrs_main.html

  23. Global AVHRR composite • 1 band in the Red: .58-.6 um • 1 band in the NIR: .72-1.1 um • Vegetation Index to map vegetation amount and productivity

  24. Remote Sensing of the Earth: Clues to a Living Planet • You can access these images over the INTERNET • http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/LAND_BIO/GLBDST_Images.html • You can either browse through individual images or watch an animation • First, click on the Global 1 degree 1986 NDVI (Climate Data Set) (1.5 MB Quicktime) animation. Open it, and click on the > button. You can go more slowly by clicking on the |> button.

  25. Remote Sensing of the Earth: Clues to a Living Planet • First, click on the Global 1 degree 1986 NDVI (Climate Data Set) (1.5 MB Quicktime) animation. Open it, and click on the > button. • Watch closely, can you observe the Green Wave in the northern hemisphere? • What about the Brown Wave? • Now look at the southern hemisphere. What do you observe?

  26. Can you see the Green Wave? http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/LAND_BIO/GLBDST_Images.html

  27. Remote Sensing of the Earth: Clues to a Living Planet • Now take a look at the Northern hemisphere in greater detail. • Click on the North America 1986 NDVI (750K quicktime) Animation. • Can you find where you live? How long does it stay green? • Compare Florida with Maine or Minnesota.

  28. North America: Close-up http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/LAND_BIO/GLBDST_Images.html

  29. Remote Sensing of the Earth: Clues to a Living Planet • To access more recently acquired AVHRR imagery go to the National Oceanographic & Atmospheric Administration (NOAA) Satellite Active Archive http://www.saa.noaa.gov/

  30. After a picture-perfect launch into space December 1999, Terra Began releasing images April 2000. Terra includes MODIS, a 2nd generation “AVHRR-like” instrument, with a number of potential applications in regional to global scale environmental monitoring of the land, ocean and atmosphere. Also includes ASTER, CERES, MISR and MOPITT. For more info go to: http://terra.nasa.gov/

  31. MODIS TERRA in Orbit http://visibleearth.nasa.gov/cgi-bin/viewrecord?133

  32. 36 discrete bands between 0.4 and 14.5 µm • spatial resolutions of 250, 500, or 1,000 m at nadir. • Signal-to-noise ratios are greater than 500 at 1-km resolution (at a solar zenith angle of 70°), and absolute irradiance accuracies are < ±5% from 0.4 to 3 µm (2% relative to the sun) and 1 percent or better in the thermal infrared (3.7 to 14.5 µm). • MODIS instruments will provide daylight reflection and day/night emission spectral imaging of any point on the Earth at least every 2 days, operating continuously. • For more info: http://eospso.gsfc.nasa.gov/eos_homepage/mission_profiles/instruments/MODIS.php

  33. 3 visible/NIR(VNIR: 0.5 and 0.9 µm) with 15-m resolution • 3 mid IR (SWIR: 1.6 and 2.43 µm) with 30-m res. • 5 TIR (8 and 12 µm) with 90-m resolution • 60- km swath whose center is pointable cross-track ±8.55° in the SWIR and TIR, with the VNIR pointable out to ±24°. An additional VNIR telescope (aft pointing) covers the wavelength range of Channel 3. By combining these data with those for Channel 3, stereo views can be created, with a base-to-height ratio of 0.6. • Overpass every 16 days in all 14 bands and once every 5 days in the three VNIR channels. For more info: http://eospso.gsfc.nasa.gov/eos_homepage/mission_profiles/instruments/ASTER.php

  34. “Aqua,” Latin for “water,” is a NASA Earth Science satellite mission named for the large amount of information that the mission will be collecting about the Earth’s water cycle, including evaporation from the oceans, water vapor in the atmosphere, clouds, precipitation, soil moisture, sea ice, land ice, and snow cover on the land and ice. Additional variables also being measured by Aqua include radiative energy fluxes, aerosols, vegetation cover on the land, phytoplankton and dissolved organic matter in the oceans, and air, land, and water temperatures.The AQUA Platform includes the MODIS, CERES and AMSR_E instruments. Aqua was formerly named EOS PM, signifying its afternoon equatorial crossing time.AQUA was launched May 2002.For more info: http://aqua.nasa.gov/

  35. ERTS-1 • Earth Resources Technology Satellite-1 • Renamed Landsat Multispectral scanner (MSS) • First images in late 1972 • Was the first civil remote sensing satellite

  36. Landsat MSS bands 4 and 5 GREEN RED

  37. Landsat MSS bands 6 and 7 Note: water absorbs IR energy-no return=black INFRARED 1 INFRARED 2

  38. MSS color composite Manhattan Rutgers • combining bands creates a false color composite • red=vegetation • light blue=urban • black=water • pink=agriculture Philadelphia Pine barrens Chesapeake Bay Delaware River

  39. Landsat 4-5 Thematic Mapper (TM)

  40. Cross-track scanning system

  41. Landsat TM-7 bands-8 bit data Spectral (where we look) Radiometric (how finely can we measure the return) 0-63, 0-255, 0-1023 Landsat TM BAND 1 2 3 4 5 7 6

  42. Spectral wavebands of Landsat TM

  43. Landsat TM: each waveband provides different information about earth surface features

  44. Thermal imagery-temperature Water analysis-nuclear power cooling ponds)

  45. Commercialization of Landsat • Landsat was commercialized by Pres. Reagan • EOSAT formed • sales dropped

  46. Landsat 7 • 15 m ETM+ (enhanced TM) sensor • April 1999 launch • Oct.’92 Land remote sensing policy act • a panchromatic band with 15m spatial resolution-fully coregistered w/30m • on-board, full aperture, 5% absolute radiometric calibration • a thermal IR channel with 60m spatial resolution • for more info go to: http://landsat.gsfc.nasa.gov/

  47. French commercial remote sensing system • First launch in 1986 • 10 and 20 m spatial resolution • 60 km swath width • Stereo viewing ability • Will have 2.5 m in 1999

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