Data Acquisition
 
1. Major remote sensing systems
        -Aerial photography
                detector
                process
                vehicle
                products: aerial photographs

        -Electro-Optical remote sensing
                detector
                process
                vehicle
                products: digital images

        -Microwave remote sensing
                uses antennas as detectors
                passive microwave systems
                active microwave systems, RADAR

        -Close range remote sensing

        -visual interpretation vs digital image processing

2. Resolutions
        Spectral resolution
        - the dimension and the number of specific wavelength
            intervals in the EM spectrum to which a sensor is sensitive

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

        Spatial resolution
        - a measure of the smallest angular or linear separation
            between two objects that can be revolved by the sensor

        Temporal resolution
        - how often a given sensor obtains imagery of a particular
            area

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

3. Color theory
   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

        -yellow, magenta, and cyan are complements of blue,
            green, and red respectively

        -various combinations of the three primaries produce
            different colors

   Subtractive primaries: yellow, magenta, and cyan
        -each absorbs its complementary color from white light
                 yellow  = white - blue
                 magenta = white - green
                 cyan    = white - red

        -superimposing yellow, magenta, and cyan dye:
                yellow  + magenta + cyan = black
                yellow  + magenta = red
                yellow  + cyan    = green
                magenta + cyan    = blue

   True-color images vs. false-color images

4. Reading: Chpt 2.7
 
 

Introduction of Satellite Systems
1. Land observation satellite systems
        Vehicles - spacecraft
        devices - sensors
        images - digital images
        target - earth resources

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

2. Satellite orbits
        circular vs. elliptic orbits

        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

        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

        inclination
        - the angle between the orbital plane and the equatorial plane
          coverage of the earth's surface

        descending node
        - the point the satellite crosses equator on southward track
            (the sunlit side of the earth)

        ascending node
        - the point the satellite crosses equator on northward track
            (the shadowed side of the earth)

        most satellites cross over the equator at about 9:30am, an
        optimal time with respect to sun angle and cloud cover

3. History
        The first earth satellite system
        - Television and Infrared Observation Satellite (TIROS)
        - an experimental weather satellite
            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

        - early Landsat (1,2,3) was named Earth Resources Technology
            Satellite (ERTS) and designated by a letter, i.e. A,B,C
        - 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

4. Reading: Chpt 6
 
 
 

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