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29 Cards in this Set
- Front
- Back
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3 useful areas of spectrum |
Visible/near/mid infrared Thermal Infrared Microwave |
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Spectral Signature |
different materials absorb different amounts of solar radiation which makes it possible to identify them based on their spectral signatures |
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What is Albedo value |
% of solar radiation reflected. |
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Polar Orbit |
WHen a satellite orbit passes over polar regions |
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Geostationary satellites |
satellites that orbit the earth in such a way that they are consistently over the same spot on earth |
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4 satellite qualities (resolutions) |
Spectral Resolution Spatial Temporal Radiometric |
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Spectral Resolution |
ability of the sensor to define wavelength intervals |
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spatial resolution |
the smallest ground area that can be discerned in an image. Related to like swath and such |
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Temporal resolution |
time it takes for a satellite to return to the same spot (16 days for landsat) |
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Radiometric Resolution |
color depth: smallest slice in which the reflectance of a feature may be assigned a digital number |
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Issues with digital image processing |
Storage display processing interpretation |
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Basic data storage |
stored as bits, bits store more info exponentially 1 byte= 8 bits which can have 256 values 2 bytes is 16 bits which can store 65,536 values unit of spatial image data is a pixel pixel value = DN |
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PCISK database elements |
Raster data is divided into channels/bands |
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Histogram |
a plot of the number of pixels at each DN within each band |
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Contrast Stretches info required |
Stat information like Min/max DN values, avg/variance/St.DEV/Histogram |
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What is a contrast stretch |
image enhancement technique that tries to improve the contrast of an image by stretching the range of intensity values |
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Image Indices |
Creating new images by combining the DN of existing images via mathematical functions |
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Vegetation indices |
they create a single nuber per pixel that predicts characteristics such as biomass, productivity, leaf area and % of vegetative ground cover |
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Filters |
a technique to extract useful information, create vector lines and identify areas of sameness |
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spatial frequency |
# of changes in brightness value per unit distance in any part of an image low frequency→smooth, gradual changes high frequency→rough, abrupt changes |
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Spatial Filtering |
Looks at surrounding DN's and adjusts your DN's |
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High pass filter |
emphasizes fine details and highlights edges |
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Low pass Filter |
emphasizes gradual change, smooths image and removes noise |
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What do you need to do Spatial Filtering? |
A kernal and an image |
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What is edge detection |
Smooths out areas of low spatial frequency and highlights edges |
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Possible methods of edge detection |
differencing, kernels, subtracting a smoothed image from the original |
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What is a kernel |
a filter that you apply to an image that makes low values lower and high values higher |
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Edge Enhancement |
adds edges back into the original image to increase contrast at the edges. IE band 4 sobel filter |
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Edge Mapping |
finds the threshold for DN's, and sets edges as either 1 or 0 for not edge |
