gus: 0265 fundamentals of gis lecture presentation 4: raster data model and operations jeremy mennis...
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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
• A raster representation is composed a series of layers, each with a theme
• Typically used to represent ‘field-like’ geographic phenomena
Raster Data Model
Raster Resolution
The distance that one side of a grid cell represents on the ground
1
22
4
4
1
1
4
4
1
1
2
4
4
1
2
3
3
3
3
2
2
2
2
2
= grid cell resolution
The higher the resolution (smaller the grid cell), the higher the precision, but the greater the cost in data storage
Raster Data:
ArcGIS
Data Compression
Common Methods:
– run length encoding– value point encoding– chain codes– block codes– quadtrees
Run Length Encoding and
Value Point Encoding
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.
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
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
Functions: Local – Single Values
Functions: Local - Mean
Functions: Focal – Immediate Neighborhood
Functions: Focal – Majority
MinMean
Functions: Zonal – Entire Zones
Functions: Zonal - Max
Functions: Global - Distance
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
Program Control: Programs
Program Control: Programs
Program Control: Programs
Program Control:
Programs
Program Control: Programs
Cartographic Modeling in ArcInfo: ModelBuilder
Locating Suitable Sites for a Waste Dump
Cartographic Modeling in ArcInfo: ModelBuilder
Cartographic Modeling in ArcInfo: ModelBuilder
Cartographic Modeling in ArcInfo: ModelBuilder
Cartographic Modeling in ArcInfo: ModelBuilder
Cartographic Modeling in ArcInfo: ModelBuilder