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Intro to Rasters
Extracted from the ESRI course
“Working with Rasters”
Contents
• What’s a Raster (or Grid)• Features vs Cells• Resolution questions• Structure• Types of Rasters
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Raster? Grid?
• Rasters may be categorized as one of two types: thematic rasters and image rasters.
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Features vs Raster
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Resolution Questions
• The output raster (Environment) should have the same (or larger) cell size as its inputs (a smaller cell size will NOT improve accuracy!).esf Laboratory for Applied GIS
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Coordinate Systems
Raster data has Three origins!
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Types of Rasters
• Thematic– Discrete (categorical, discontinuous)– Continuous
• Image– Satellite– Aerial photographs
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Thematic Rasters
• Represent objects that have definable boundaries, like buildings, wells, land parcels, lakes, etc.
• May represent a characteristic of features instead of the features themselves.
• May or may not have an attribute table (called a Value Attribute Table (VAT)
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Continuous Rasters
• Data that varies continuously over the raster like elevation, pollution levels, noise, etc.
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Image Rasters
• "image" usually refers to values that represent the intensity of reflected visible light or other radiation (infrared, etc.)
• Data may consist of one “band” (Panchromatic or simply Pan) or many bands ( Composite)
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Composite Image
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But this is Remote Sensing Stuff