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Geographic Information Systems

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Geographic Information Systems

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    1. Geographic Information Systems GIS Data - Remote Sensing

    2. Remote Sensing Definition

    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

    6. Properties .. Major divisions of EM spectrum X-rays, UV, visible, infrared, microwave, TV

    7. Properties .. From http://rst.gsfc.nasa.gov/Intro/nicktutor_I-3.html

    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

    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

    10. Properties ..  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 ..

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

    14. Properties

    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

    18. 3 (2) Electro-Optical Remote Sensing Electro-Optical scanners Uses light-sensitive detectors Generates electrical signals Mounted on spacecrafts or aircrafts

    21. 3 (3) Microwave Remote Sensing Uses antennas as detectors Passive microwave systems Active microwave systems, RADAR

    23. 4. Operation of Digital Remote Sensing Moving mirror and pushbroom

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

    25. 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

    26. Operation ..

    27. Operation

    28. 5. Types of Resolution Spectral resolution Radiometric resolution Spatial resolution Temporal resolution

    29. 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

    30. 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

    31. 5(3) Radiometric Resolution The sensitivity of a detector to differences in signal strength as it records the radiant levels

    32. 5(4) Temporal Resolution How often a given sensor obtains imagery of a particular area, e.g., 16 days, daily

    33. 6. Commonly Used Satellite Image Data Moderate resolution land satellites Landsat SPOT

    34. 6. Commonly Used Satellite Image Data High resolution land satellites IKONOS OrbView GeoEye QuickBird

    35. 6. Commonly Used Satellite Image Data .. Meteorological satellites AVHRR EOS

    36. 6. Commonly Used Satellite Image Data .. Radar systems RADARSET LIDAR

    37. 6. Commonly Used Satellite Image Data .. Digital aerial photographs DOQQ

    38. Readings Chapter 8

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