Lab 2: GIS Data Models

Lab 2: GIS Data Models
Yingjie Hu
• Understanding GIS data models
• Manipulating the data models supported in
Data Models
• An abstraction of the objects in the real world
– Points --> trees
– Lines --> roads
– Image --> elevation (Digital Elevation Model)
Data Models
• Vector
– Points, lines, areas
– discrete, but can be used for continuous
• Raster
– Grid cells with one value per cell
– Continuous
• TIN (Triangulated Irregular Network )
– a series of triangles with each node having an xyz
– representing surface
Data Structures vs. Data Models
• Data model
– set of constructs for describing and representing
selected aspects of the real world in the computer.
• Data structure
– How the data model actually stored on computers
• The same data model can be expressed in
different data structures
– E.g. both CAD data and ArcGIS Shapefile can represent
the vector data model
Data models in ArcGIS
• ArcGIS supports the three GIS data models
(vector, raster, and TIN)
• ArcGIS also provides three specific data
– Shapefile
– Coverage
– Geodatabase
Data models in ArcGIS
• Shapefile
– Vector model
– A single geographic feature type (counties, roads,
cities, etc.)
– Does not have topology
Data models in ArcGIS
• Coverage
– Vector model
– Contains multiple geographic feature types, and
each type is a feature class (counties, roads, cities).
Different feature classes share the same theme.
– Have topology
Data models in ArcGIS
• Geodatabase
– Vector and Raster
– Multiple feature classes
– Feature datasets, relationship classes, topologies,
networks, etc.
Data model conversion
• ArcToolbox
– Raster --> Polyline
– Raster --> Polyline--> Coverage
To Hand in
• Hand in through Gauchospace
– The question sheet, with typed answers
– One map of Santa Barbara roads and contours
• Due: Next Wednesday (Feb. 1st)