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