Intro to Rasters
Extracted from the
ESRI course
“Working with
Rasters”
Contents
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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!).
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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
But this is Remote Sensing Stuff
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