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Remote Sensing

Electromagnetic Waves. Examples of electromagnetic waves:Red lightGreen lightX raysGamma raysRadio wavesElectromagnetic waves are moving altered fields of space' that exert a physical force on electrically charged objects in the field.. An electromagnetic Wave. . . . amplitude. The amplitude

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Remote Sensing

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    1. Remote Sensing Introduction to light and color. What is remote sensing? Introduction to satellite imagery. 5 resolutions of satellite imagery. Satellite image display.

    2. Electromagnetic Waves Examples of electromagnetic waves: Red light Green light X rays Gamma rays Radio waves Electromagnetic waves are moving ‘altered fields of space’ that exert a physical force on electrically charged objects in the field.

    3. An electromagnetic Wave

    7. What makes objects a certain color? The color of an object is determined by how much light it reflects of each wavelength in the visible light portion of the EM spectrum. Some objects emit light as well, greatly affecting their color. Objects reflect some wavelengths. Objects absorb some wavelengths.

    8. Spectral Signatures

    9. Remote Sensing Remote sensors are devices that sense energy from a remote location (i.e., a device not in physical contact with what it is sensing) Remote sensing is the science of acquiring, processing and interpreting information/data collected by remote sensors.

    10. Remote Sensing Active – emit energy and detect reflections Sonar Radar Lidar Passive - detect emitted/reflected energy from other sources Satellite sensors Air photos Cameras Video recorders

    11. Satellite Imagery Digital data is obtained by sensors on satellite platforms.

    12. Satellite Imagery Described by five resolutions Spatial resolution: area on ground represented by each pixel Advanced Very High Resolution Radiometer (AVHRR) – 1 km Landsat - 30m SPOT – 2.5m - 20m / 2.5m - 10m IKONOS - 1m/4m Temporal resolution: how often a satellite obtains imagery of a particular area Spectral resolution: specific wavelength intervals in the electromagnetic spectrum captured by each sensor Radiometric Resolution: number of possible data values reportable by each sensor (how sensitive the sensor is to changes in brightness of objects that it views) View angle resolution: the number of angles at which the ground objects are recorded by the sensor.

    17. Temporal Resolution Number of days between overhead passes at the same location Landsat - 16 days AVHRR - daily IKONOS - 1 to 3 days

    18. Spectral Resolution

    19. Review: Electromagnetic Spectrum A continuum of all possible energies that radiate through space In remote sensing, we mainly focus on visible, infrared and microwave

    20. Landsat spectral resolution

    21. Spectral Regions – Landsat MSS Blue Visible - Used for bathymetry - water penetration to about 50m in clear water. Necessary for a true color image Blue Visible - Used for bathymetry - water penetration to about 50m in clear water. Necessary for a true color image

    22. Band 1 is used with bands 2 and 3 to construct true color composites to assess a variety of features. Band 1 is used with bands 2 and 3 to construct true color composites to assess a variety of features.

    23. Green Visible - Peak chlorophyll reflectance band, used for vegetation analysis. Also bathymetry - water penetration to about 40m. Green Visible - Peak chlorophyll reflectance band, used for vegetation analysis. Also bathymetry - water penetration to about 40m.

    24. Band 2 is used with bands 1 and 3 to construct a true composite and bands 3, 4, and 7 to construct near and shortwave infrared composites to assess a variety of features. Band 2 is used with bands 1 and 3 to construct a true composite and bands 3, 4, and 7 to construct near and shortwave infrared composites to assess a variety of features.

    25. Red Visible - Provides added value information to vegetation analysis. Red Visible - Provides added value information to vegetation analysis.

    26. Band 3 is used with bands 1 and 2 to construct true color composites and bands 4 and 2 to construct near infrared composites to assess a variety of features. Band 3 is used with bands 1 and 2 to construct true color composites and bands 4 and 2 to construct near infrared composites to assess a variety of features.

    27. Near Infrared - This is the primary band used to assess vegetation. Analysts can also assess camouflage detection and land water delineation using band 4. Near Infrared - This is the primary band used to assess vegetation. Analysts can also assess camouflage detection and land water delineation using band 4.

    28. Band 4 is used with bands 3, 5, 7 and 2 to construct near and shortwave infrared composites to assess a variety of features. Band 4 is used with bands 3, 5, 7 and 2 to construct near and shortwave infrared composites to assess a variety of features.

    29. Short-wave Infrared - Camouflage detection, change detection, vegetation analysis. Short-wave Infrared - Camouflage detection, change detection, vegetation analysis.

    30. Band 5 is used extensively with bands 3, 4, 6, and 7 to construct shortwave and longwave infrared composites to assess a variety of features. Band 5 is used extensively with bands 3, 4, 6, and 7 to construct shortwave and longwave infrared composites to assess a variety of features.

    31. Mid-wave Infrared. Mid-wave Infrared.

    32. Band 7 is used extensively with bands 2, 4, 5, and 6 to construct shortwave and longwave infrared composites to assess a variety of features.Band 7 is used extensively with bands 2, 4, 5, and 6 to construct shortwave and longwave infrared composites to assess a variety of features.

    33. Long-wave Infrared - Thermal analysis. Long-wave Infrared - Thermal analysis.

    34. Landsat has the ability to sense EM radiation in the LWIR region using band 6. This band has a GSD of 120 meters. It can be useful for geologic mapping, vegetation classification, vegetation stress detection, soil moisture content, fire management, thermal pollution, and ocean current studies. Band 6 is used with bands 5 and 7 to construct longwave infrared composites to assess a variety of features. Landsat has the ability to sense EM radiation in the LWIR region using band 6. This band has a GSD of 120 meters. It can be useful for geologic mapping, vegetation classification, vegetation stress detection, soil moisture content, fire management, thermal pollution, and ocean current studies. Band 6 is used with bands 5 and 7 to construct longwave infrared composites to assess a variety of features.

    35. Review the differences in features between the bands.Review the differences in features between the bands.

    36. Spectral Resolution of Landsat TM

    37. Radiometric Resolution Number of possible data values reported by the sensor Range is expressed as a power (2n ) 8-bit resolution has 28 values, or 256 values Range is 0-255 12-bit resolution has 216 values, or 65,536 values Range is 0-65535 The value in each pixel is called the Digital Number (DN) Brightness Value (BV)

    38. Image Display Graphics display devices use three color guns Red, Green, Blue All colors can be formed from various combinations of these 3 colors (which is why they’re used in computer/TV screens) The brightness values (BV) to be displayed will often have an 8-bit range 0 to 255 In remote sensing, we assign one band to each color gun to give color to the image

    39. Image Display For a single band, the resultant color will be grayscale All three colors display the same value, so the colors are shades of gray

    42. Image Display For a multi-band image, the resultant color will depend on which bands are assigned to which color guns

    43. Multispectral Imagery Display Composite images are constructed in a manner directly related to the actual imagery display process. Starting from the bottom of the slide and working our way up, we begin with the raw spectral bands, in this case Landsat TM bands. No matter how many bands a system has, you can only view three of them at one time. The reason for this is that all (color) display monitors utilize a combination of three color guns to produce an image. These color guns are always red, green, and blue, (RGB) respectively. If for example, we wanted to produce an image with the band combination of 7-4-2 (the NIMA standard composite), the data (energy) from band 7 would be shot through the red color gun, band 4 through the green gun, and band 2 through the blue gun. Composite images are constructed in a manner directly related to the actual imagery display process. Starting from the bottom of the slide and working our way up, we begin with the raw spectral bands, in this case Landsat TM bands. No matter how many bands a system has, you can only view three of them at one time. The reason for this is that all (color) display monitors utilize a combination of three color guns to produce an image. These color guns are always red, green, and blue, (RGB) respectively. If for example, we wanted to produce an image with the band combination of 7-4-2 (the NIMA standard composite), the data (energy) from band 7 would be shot through the red color gun, band 4 through the green gun, and band 2 through the blue gun.

    44. Color composite image

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