Remote Sensing and Geophysical Field Methods involve indirectly retrieving data about the earth surface and subsurface using electromagnetic waves.
SONAR (Sound Navigation and Ranging)
SONAR uses sound waves to detect the location or speed of an object.
Side Scan Sonar emits pulses of sound waves on to the seafloor. It detects reflections of those waves off materials and items on the seafloor, records them and then plots them so that the results look like a picture of a swath of seafloor. Because the transducers that emit the sound waves are set at angle in the tow vehicle, no image is created directly under it. Side Scan Sonar can be used to detect reefs, shipwrecks and other underwater structures on the seafloor.
Sub-Bottom Profilers emit pulses of sound waves into the seafloor. It detects reflections of those waves off sediments and items on and below the seafloor, records them and then plots them so that the results look like slice down through the seafloor. Because the sound waves are reflected differently through the layers of sediment and rock, this method is used to find geologic structures such as subsurface karst features and ancient river channels.
RADAR (Radio Detecting And Ranging)
RADAR uses ultra-high frequency radio waves or microwaves to detect the location or speed of an object.
Doppler Radar uses microwaves and the change in frequency (Doppler effect) to help meteorologists measure the size and speed of large storms.
Ground Penetrating Radar emits pulses of radio waves into the ground. It detects reflections of those waves off materials and structures under the ground, records them and then plots them so that the results often look like a slice down through the earth. Because both freshwater and fiberglass are transparent to the radio waves used, GPR can be used in lakes.
LiDAR (Light Detection and Ranging)
LiDAR uses light in the form of a laser, most frequently collected from an aircraft, to obtain a 3D scan of the earth’s surface. When LiDAR data is collected and processed, scientists can develop detailed models of surface elevations, which has important applications toward understanding coastal erosion, flood zones, patterns of sinkholes, and water resources. Many applications of LiDAR exist outside of the geosciences as well.
Thermography is a remote sensing method of visualizing Earth’s temperature signature over various terrains and geographic scales. There are both active and passive methods of obtaining thermographic datasets. The more common methods of acquiring thermography data include using multispectral scanners and/or infrared scanners. These scanners and other special equipment are typically attached to an aircraft and flown over a study area or area of interest. These scanners are also attached to satellites to monitor greater spans of area. This technology is used to detect flowing fresh-water springs and forest fires, monitor urban temperatures, identify stresses on vegetation, monitor weather and study weather patterns, study the impact of insects on crops, and even help identify potential structural integrity issues of buildings and bridges.
March 16, 2021 - 3:12pm
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