Lab 2: GIS Data Models Yingjie Hu

Objectives Understanding GIS data models Manipulating the data models supported in ArcGIS

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 models – 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)