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GIS
Geographic information system: integrates hardware, software, and data for capturing, managing, and displaying all forms of geographically referenced information
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Raster
Grid. Cells that each have a state/contain information
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Vector
Point, line, polygon. Gives us just what we want (like lines on a map representing roads)
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Attribute
Non-spatial data. Attributable and assigned to spatial locations (ex. names, populations attached to any point).
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Geographic
Earth's surface and near-surface
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Spatial
Any space (including geographic) ex. medical imaging
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First GIS
Canada Land Inventory (1960)
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Landsat 1 (ERS-1)
Launched in 1972, first orbital satellite that was designed for environmental studies
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Remote Sensing
- Gathering of data about the earth and environment by satellite sensors
- Using information that's contained in the electromagnetic radiation reflected from an object
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Scene
Volume of area, object of interest
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Temporal Resolution
Orbital characteristics; how often a certain satellite revisits a certain location
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radiometric resolution
the fineness of the chunks of waves a sensor can identify
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spatial resolution
- pixel size, ex. digital camera resolution
- the more pixel resolution, the more detailed
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active sensors
sensor itself provides the energy initially needed as well as receiving
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Passive sensors
relies on the sun as the source for electromagnetic radiation
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metadata
data about the data (so meta)
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Image resolution
resolution quantifies how close lines can be to each other and still be visibly resolved
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Types of imaging systems in remote sensing
- frame
- scanner
- pushbroom
- whiskbroom
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IFOV
instantaneous field of view, area of the ground viewed at one spot
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endmember spectra
examples of the spectra from the pure individual elements within a pixel
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vertical aerial photography
- determination of distances, areas, and directions
- importance of precise height and attitude(?) information
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Wavelength
distance from one peak to the next
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frequency
number of peaks passing a fixed point over a period of time
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amplitude
height of each peak (related to energy and brightness)
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velocity of light (c) =
frequency (v) x wavelength (lambda)
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Visible light spectrum wavelengths
400nm-700nm
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Blackbody radiation
- "perfect absorber" (also perfect emitter)
- all materials emit radiation at a given temp and frequency exactly as well as it absorbs the same radiation
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the blackbody spectrum
the shape of the blackbody radiation curve is the same at all temperatures
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The dividing line b/w reflected and emitted IR wavelengths is about _____
3um (3000nm)
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Reflection
when a ray of light is redirected as it strikes a surface
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specular reflection
surface is smooth relative to the wavelength
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diffusive reflection
when the surface is rough relative to the wavelength
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Raleigh scattering
particles are smaller than wavelength of light, more scattering, more absorbance
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Mie scattering
particles are about same size as wavelength of light, similar amount of each wavelengths comes through (whiteness of clouds)
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Non-selective scattering
particles are bigger than the wavelengths of light, lets us see dark things like smog, smoke, etc.
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Absorption band
range of wavelengths in the EM spectrum in which radiant energy is absorbed by a substance
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Close-downs
regions of the spectrum in which the atmosphere is absorbing all the EM energy are not visible from space
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Windows
regions of the EM spectrum where the atmosphere is absorbing little or not at all. EM energy can be used to observe the surface of the earth.
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Radiance
Information received by sensor (in watts per square meter per steradian)
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reflectance
ratio of reflected versus incoming radiant flux (ex. brighter a surface the higher its reflectance)
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Registration
Making two image layers correspond (same scale, making sure they line up)
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Georeferencing
- Process of assigning map coordinates to image data
- Giving it spatial coordinates
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Orthorectification
3D terrain correction
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2-step process of rectifying geometric distortions and projecting the data onto a 2D plane
- 1. Rectification
- 2. Resampling
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GCP
Ground control points: x, y coordinates of known locations
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Nearest Neighbour
Assigns a pixel value based on nearest pixel in original matrix to a given pixel in the output matrix
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Bilinear interpolation
assigns a value based on a weighted linear average of the 4 nearest pixels in the original matrix
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Cubic Convolution
Assigns a value to a given cell in the output matrix based on a 4x4 moving average calculated using a cubic polynomial
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Spectral Resolution
a measure of the ability of a spectrometer to resolve features in the electromagnetic spectrum
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Spectral bands
the regions (bands) of the EMR that are detected by the sensor
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Multispectral sensors
Characterized by relatively small number of spectral bands (<30)
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Hyperspectral sensors
Characterized by hundreds of narrow spectral bands (>200)
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Radiometric Resolution
- The sensitivity of a sensor to differences in signal strength/radiance
- the number of gray tones in a range
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Geostationary orbit
- Seem stationary above earth because they revolve with the same speed as the earth over the equator
- ex. weather satellites
- can get as high a temporal resolution as you want
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Polar orbit
- Move North-South and pass close to poles
- only record data in the ascending pass (moving northward)
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Sun-synchronous orbit
- Polar orbit that covers each area of the world at a constant local time of day called sun time
- always in light
- can collect data 24/7
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Supervised Classification
- Identifying spectrally similar areas on an image by identifying "training" sites of known targets, then using those spectral signatures to classify other areas of unknown targets
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Unsupervised Classification
Categorization of digital image data based solely on the image statistics w/out availability of training sites, no prior knowledge of the area
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Image classification
Grouping image pixels from different spectral bands into categories or classes
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NDVI
Normalized Difference Vegetation Index
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Absorption =
incoming radiation - (reflection + transmission)
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Important plant pigments
Chlorophyll a and b, carotenoids,
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State Change: Compositing
ex. takes vegetation index data from 3yrs of forest fire data
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Delta Classification
Following actual classification
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Spectronomics
Spectral mapping of taxonomic diversity
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Remote sensing of the atmosphere: most important variables
- Clouds
- Humidity
- Precipitation
- Aerosols
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Higher clouds are _______
Colder
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GOES
Geostationary Operational Environmental Satellite
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AVHRR
Advanced Very High Resolution Radiometer
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LiDAR
- Light Detection and Ranging
- wavelengths of 400-1500nm
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Cloudsat
- Cloud profiling radar CPR
- Uses microwaves
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