GIS Data Modeling
Transcript of GIS Data Modeling
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GIS Data Modeling
• What is a data model?
• GIS data models
- CAD (Computer Aided Design)
- Raster data model
- Vector data model
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What is a data model?
• The heart of any GIS is the data model.
• A data model is a set of constructions for describing and representing selected aspects of the real world in a computer.
• model that is best for all cases
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The role of a data model in GIS
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Levels of data model abstraction
• Reality: real world phenomena
• Conceptual model: human-oriented model of selected objects
• Logical model: implementation-oriented representation of reality, often expressed in the form of diagrams and lists
• Physical model: portrays the actual application in a GIS, often include tables stored as files or databases.
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GIS data models
• CAD (Computer Aided Design)
• Raster data model
• Vector data model
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The CAD data model
• A CAD model focuses on feature drawing only so that it does not represent any kind of relationships between objects.
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graphical and image GIS data models
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Raster data model
• Raster data model uses an array of cells, or pixels, to represent real-world objects.
• Difference between raster and image data models:
1. Image data do not have attribute table attached
2. Raster data have attribute table
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Vector data model
• Simple features
• Topological features
• Network data model
• TIN data model
Vector representations
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Topological features
• Topological features are simple features
• structured using topological rules.
• Topology is the science and mathematics of relationships. In GIS, topology is used to validate the geometry of vector datasets.
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Network data model
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TIN (Triangulated Irregular Network)data model
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Vector Data Structure
• Point • Line• polygon
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Geographical data are spatial data
• Spatial data = Objects with some form of spatial structure
• They have positions in X, Y, (Z) - Longitude,
• Latitude, (Elevation)
• (Roads, buildings, plants, lakes)
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But, data can also be:
Non-spatial
Attribute Data:Data that describe the properties of the object For example: Building owner; Population of a city.
Types of Attribute Data:TablesTextDocumentsPicturesVideoSound, etc.