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Intro to Rasters Extracted from the ESRI course “Working with Rasters”

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Intro to Rasters Extracted from the ESRI course “Working with Rasters”
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Page 1: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

Intro to Rasters

Extracted from the ESRI course

“Working with Rasters”

Page 2: 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

esf Laboratory for Applied GIS

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Page 3: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

Raster? Grid?

• Rasters may be categorized as one of two types: thematic rasters and image rasters.

esf Laboratory for Applied GIS

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Page 4: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

Features vs Raster

esf Laboratory for Applied GIS

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Page 5: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

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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Page 6: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

Coordinate Systems

Raster data has Three origins!

esf Laboratory for Applied GIS

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Page 7: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

Types of Rasters

• Thematic– Discrete (categorical, discontinuous)– Continuous

• Image– Satellite– Aerial photographs

esf Laboratory for Applied GIS

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Page 8: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

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)

esf Laboratory for Applied GIS

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Page 9: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

Continuous Rasters

• Data that varies continuously over the raster like elevation, pollution levels, noise, etc.

esf Laboratory for Applied GIS

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Page 10: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

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)

esf Laboratory for Applied GIS

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Page 11: Intro to Rasters Extracted from the ESRI course “Working with Rasters”

Composite Image

esf Laboratory for Applied GIS

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But this is Remote Sensing Stuff


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