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Hyperspectral Imagery Collection |
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What is HyperSpectral Imaging
HyperSpectral Imaging (HSI) remote sensing produces images of the earth's surface similar to how a camera produces photographs; however, unlike cameras that collect information in the three bands of red, green, and blue, hyperspectral sensors simultaneously collect data in hundreds of spectral bands to produce an image. These measurements are used to identify and quantify features in an image that could not otherwise be studied in traditional aerial imagery. |
Data Collection
HSI remote sensing is performed by mounting a spectral imaging sensor on a distant platform such as a ship, spacecraft, or as in the CICORE program, an aircraft. The sensor records the amount of electromagnetic radiation (light) that is reflected from the earth’s surface to the sensor. |
Atmospheric Corrections
Sunlight passes through the earth's atmosphere, reaches the earth’s surface, and is reflected, again passing through the atmosphere. The light is modified by each pass through the atmosphere. We collect both upwelling radiance and downwelling irradiance in the aircraft and on the ground in order to determine how transmission through the atmosphere affects the true color of the light. We use this data with a variety of atmospheric models to correct the imaging sensor data to the true color of the surface reflectance, which provides the starting point for advanced algorithms and imaging products for ecological management. |
Geo-Location
Finally, the position of every image element must be accurately located in map coordinates on the earth's surface; this process is called geo-location. FERI uses high precision GPS and inertial motion instruments to locate the craft in space and time as well as to identify where the sensor is pointed, such that each image pixel may be accurately mapped to an exact location. Over a flat surface like water, geo-location is relatively straightforward, since all sensor viewing angles and ground intersections are relatively easy to model. Consequently, a relative simple process called geo-rectification is used to geo-locate the pixels. However, with the significant elevation changes common to California's terrain, a more complex solution is required that uses the orthometric height of the landscape to precisely locate the intersection of the viewing angle of the sensor with the ground. This geo-location process is called ortho-rectification and combines more precise instrumentation with specialized software and digital elevation maps in order to more accurately geo-locate the imaging products. |
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