Satellite Mapping
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  • 1. Notes on Ch. 9 & 10Satellite Mapping of Earth Resources and Earth’s Atmosphere and Water Resources
  • 2. Natural resource analysis has never had a high priority in satellite funding.
    Highest priorities: Defense, National Security, Communications, Commercial, Weather.
    A great deal of analysis has been done with limited resources.
    The CIA and Pentagon have the best toys.
    Some Remarks
  • 3. Started in 1972.
    First called ERTS (Earth Resource Technology Satellite) Figure 9-1 Landsat vehicles.
    System designed to follow a specific orbit that would bring it back over the same locus on the Earth’s surface, thereby providing repetitive coverage to monitor change through time. See Figure 9-2.
    Returns to a specific location every 18 days.
  • 4. Primary tool of Landsat.
    Records reflected and/or radiated energy from the Earth simultaneously in four contiguous bands of the EMS.
    Provides multiple data sets to produce geographically registered images (one for each band).
    Each scene covers 115 miles by 115 miles (185km) in the shape of a parallelogram.
    Overlap provided between scenes.
    Multispectral Scanning System (MSS)
  • 5. Differences in the bands sensed between the different LandsatS. See Figure 9-3.
    The bands on the MSS can be selected to give the same results as Color Infrared Film (CIR)
    MSS (continued)
  • 6. Picture element.
    The smallest area on the ground that is detected by a sensor.
    A general measure of the sensitivity of a digital scanner
    The MSS on the first three Landsats could detect a minimum of 79 sq. meters. The value recorded is the average reflectance for the pixel.
  • 7. This is a fairly coarse density.
    To see an object on MSS it should normal be about twice the width of a pixel. Objects with great contrast can be seen at single pixel density.
    MSS data needs extensive processing to create a useful image.
    Pixel (continued)
  • 8. Starting on Landsat 4 a new scanner.
    Offered increased ground resolution, a greater number of spectral bands, and faster return time to image a particular Earth surface location (16 days vs. 18)
    Spectral bands modified to improve detection of soil, rock , and vegetation.
    Ground resolution improved to 30meters
    Thematic Mapper (TM)
  • 9. Assigning the reflectance values of data from sensed bands to the standard red, green, and blue layers of color film using filters.
    A common technique with satellite data.
    False Color Images
  • 10. A European (French) natural resource satellite
    Système Pour L’Observation de la Terre
    Started in 1977. SPOT 1 launched in 1986.
    First big job: acquiring images of the Chernobyl accident in the Soviet Union in May.
  • 11. Orbital path similar to Landsat. Sunsynchronous (passing over the same latitude at the same local time). Required 26 days to return to the same location.
    Has higher resolution than Landsat, but the area of one scene is much smaller.
    SPOT (continued)
  • 12. Panchromatic: 0.5 to 0.73 micrometers. See EMS on Fig. 3-1. Ground resolution of 10m squared.
    Multispectral: 0.5-0.59 green, 0.61 to 0.68 red, and 0.79 to 0.89 micrometers IR. Pixel resolution 20m squared.
    Adjustable viewing angle 27o east or west of the orbital path. Allows for the creation of stereo pairs.
    Sensors on SPOT
  • 13. Large format camera on Space Shuttle. Multi-camera system to provide cartographic quality images. Can exactly locate position on earth’s surface and the nadir of the image.
    Shuttle hand-held photography.
    Advantages and Disadvantages of imagery from manned flights???
    NASA Manned Flight Images
  • 14.
    Landsat program home page:
    Web Links
  • 15. Weather forecasting. (fire fighting)
    Climate changes
    Pollution and particulate matter.
    Figure 10-1 and 2. Satellites and sensing tools.
    Satelite mapping of Earth’s Atmosphere and Water Resources
  • 16. Most of these satellites focus on the visible, reflected IR, and thermal IR portions of the EMS. Fig. 10-3 shows the transmission windows.
    Types of operational satellites (Figure 10-4):
    Polar orbiters- follows path roughly parallel to the earth’s axis from pole to pole.
    Geostationary – orbit and speed that positions them above any point on the Earth where they maintain position constantly
    Spectral Bands Utilized
  • 17. Known by acronym GOES – Geostationary Operational Environmental Satellite. Several in service since 1975
    Day-night capability. Sensor is VISSR – Visible-Infrared Spin-Scan Radiometer). Records energy in:
    One visible band: 0.55 – 0.70 microns
    Thermal IR 10.5 – 12.5 microns
    Geostationary Weather Satellites
  • 18. Figure 10-7 full disc visible image of part of the earth and its cloud cover
    All clouds at any elevation show up in this image.
    Allows nephanalysis – the study of cloud patterns and formations.
    GOES continued
  • 19. Figure 10-8 full disc infrared image.
    Images have geographic grid of meridians and parallels and continent and political boundaries
    Full disc IR shows thermal values for land, water, and clouds.
    Polarity of gray tones shows warmer temperatures as dark and colder temperatures as light.
    Coldest, highest clouds are white. Lower clouds dark. Most unstable clouds most visible.
    GOES continued
  • 20. The visible and thermal IR images combined give good cloud information. Can be compared day to day.
    Comparing areas with or devoid of clouds can show high pressure and low pressure areas.
    Water vapor imagery. Uses energy radiated in the 6.7 micron band. At this wavelength the radiation is absorbed and reradiated by water in the gaseous state.
    GOES satellite viewer:
    NOAA Weather forecast for Mont Alto, PA
    GOES continued
  • 21. Numerous satellites and scanners have been used to sense environmental data since 1060
    Some of the products include:
    Temperature soundings in the atmosphere
    Ice analysis in the polar regions and Great Lakes
    Vegetation index
    Snow cover
    Tropical cyclones
    Polar Orbiter Satellites