GUS: 0265 Fundamentals of GIS

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GUS 0265Fundamentals of GIS

• Lecture Presentation 4
• Raster Data Model and Operations
• Jeremy Mennis
• Department of Geography and Urban Studies
• Temple University

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Raster Data Model

• A raster representation is composed a series of
  layers, each with a theme
• Typically used to represent field-like
  geographic phenomena

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Raster Resolution

• The distance that one side of a grid cell
  represents on the ground

grid cell resolution
The higher the resolution (smaller the grid
cell), the higher the precision, but the greater
the cost in data storage
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Raster Data ArcGIS
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Data Compression

• Common Methods
• run length encoding
• value point encoding
• chain codes
• block codes
• quadtrees

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Run Length Encoding and Value Point Encoding
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Map Algebra and Cartographic Modeling

• A raster modeling language, and an approach to
  GIS analysis design, developed by J.K. Berry and
  C. Dana Tomlin in the late 1970s - early 1980s.
• It now forms the basis for grid-based analysis in
  ArcInfo (GRID and Spatial Analyst) and other GIS
  packages.

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Map Algebra

• A set of formally defined manipulations on raster
  data.
• Operators Fundamental mathematical and logical
  operations on raster data
• Functions Complex combinations of operations

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Functions Types
Higher order data manipulations on raster grids
built from the more basic operators. Local
compute on single-cell basis Focal compute on a
neighborhood Zonal use zones derived from a
separate grid for evaluation Block like zonal,
but the result is assigned to an entire block
of cells Global compute on the entire grid
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Functions Local Single Values
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Functions Local - Mean
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Functions Focal Immediate Neighborhood
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Functions Focal MajorityMinMean
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Functions Zonal Entire Zones
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Functions Zonal - Max
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Functions Global - Distance
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Program Control Statements and Programs
Statement notation to represent operations and
functions e.g. NEWLAYER LocalFUNCTION of
FIRSTLAYER and SECONDLAYER Program notation to
represent a procedure i.e. a sequence of
statements in which each statement operates on
the result of a previous statement
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Program Control Programs
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Program Control Programs
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Program Control Programs
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Program Control Programs
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Program Control Programs
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Cartographic Modeling in ArcInfo ModelBuilder
Locating Suitable Sites for a Waste Dump
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Cartographic Modeling in ArcInfo ModelBuilder
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Cartographic Modeling in ArcInfo ModelBuilder
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Cartographic Modeling in ArcInfo ModelBuilder
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Cartographic Modeling in ArcInfo ModelBuilder
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Cartographic Modeling in ArcInfo ModelBuilder