GEOG 330 Chapter 9 - 1/9 GEOG 330 INTRODUCTION TO REMOTE...

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GEOG 330 INTRODUCTION TO REMOTE SENSING Ch 9 Microwave Remote Sensing 1/9
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Passive and Active Remote Sensing ! Passive remote sensing systems record electromagnetic energy that was reflected (B, G, R, NIR, SWIR) or emitted (thermal IR) from the surface of the Earth. ! Active remote sensors create their own electromagnetic energy that 1) is transmitted from the sensor toward the terrain (and is largely unaffected by the atmosphere), 2) interacts with the terrain producing a backscatter of energy, and 3) is recorded by the instrument’s receiver. 2/9
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Active Remote Sensing Systems The most widely used active remote sensing systems include: ! Active microwave ( RADAR ), which is based on the transmission of long-wavelength microwaves (e.g., 3 – 25 cm) through the atmosphere and then recording the amount of energy back-scattered from the terrain and when it is received. ! LIDAR , which is based on the transmission of relatively short- wavelength laser light (e.g., 0.90 mm) and then recording the amount of light back-scattered from the terrain. ! SONAR , which is based on the transmission of sound waves through water and then recording the amount of energy back- scattered from the bottom or from objects within the water column. 3/9
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History of Microwave (RADAR) Remote Sensing Systems ! RADAR as we know it today was first investigated by Taylor and Young in 1922 with the creation of a long wavelength radio (1 – 10 m) transmitter that helped to detect the distance to ships at sea at night or during bad weather. ! The phrase describing the process was “ ra dio d etection a nd r anging or RADAR . ! Although RADAR systems now use microwave wavelength energy instead of radio waves, the acronym was never changed. 4/9
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History of Microwave (RADAR) Remote Sensing Systems ! The continuous-strip mapping capability of side-looking airborne radar ( SLAR ) was developed in the 1950s. ! SLARs started to be used in the 1960s for rapid Earth resource reconnaissance mapping of vast, previously unmapped regions. Early mapping efforts focused on regions with permanent cloud cover (Central America, the Amazon, Equatorial Africa). ! The first orbital synthetic aperture radar (not classified) that provided public-domain data was SEASAT , which was launched by NASA in 1978 to obtain L-band (23.5 cm) 25 x 15 m spatial resolution oceanographic information. 5/9
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RADAR Remote Sensing ! Active microwave energy penetrates clouds and can be an all- weather remote sensing system. ! Synoptic views of large areas for mapping at a range of scales. ! Coverage can be obtained at user-specified times (airborne), even at night. ! Senses in wavelengths outside the visible and infrared regions of the electromagnetic spectrum, providing information on surface roughness, dielectric properties, and moisture content. 6/9
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GEOG 330 Chapter 9 - 1/9 GEOG 330 INTRODUCTION TO REMOTE...

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