AIM: To introduce various GIS data models After this lecture you should be able to: Describe the primary Vector data models used in GIS and give examples Describe raster data models and give examples Describe TIN data models Explain “topology” Describe the main file formats used in GIS
Lecture 3: GIS Data Models AIM: To introduce various GIS data models After this lecture you should be able to: Describe the primary Vector data models used in GIS and give examples Describe raster data models and give examples Describe TIN data models Explain “topology” Describe the main file formats used in GIS Graphic Features Objects which are shown on a map are called graphic features or features These features may be natural or man made objects Graphic Features Digital representation of physical or man made elements: Vectors Points or Nodes Lines or Arcs Polygons Raster Cells or Pixels Images Digital Orthophotography Geographic Data Types Images Vector Raster (GRID) Attributes TIN (Triangulated Irregular Network) Annotation © Paul Bolstad, GIS Fundamentals Geographic Data Types © Paul Bolstad, GIS Fundamentals DIGITAL SPATIAL DATA • RASTER • VECTOR • Real World Source: Defense Mapping School National Imagery and Mapping Agency Electronic Maps in Raster and Vector Formats Raster Data Sources Air Photos Satellite Imagery Scanned Maps Digital Orthophotograph A scanned photograph that has been mathematically rectified to eliminate the effects of displacement so that its view always appears as though it is perpendicular to the ground Image Copyright 1993 Nassau County, NY © ESRI, Modeling Our World © ESRI, Modeling Our World Annotation Text or labels plotted on a map which describe or identify a feature or add other information to the map Annotation Text Information placed on a map to provide additional information about a graphic feature Symbols The means by which graphic features are displayed in a GIS Symbols Symbols help identify features and provide information about them qc,PX Annotation, Symbology, and Text Courtesy Village of Garden City Issues of Scale in Feature Representation Depending upon the presentation scale, a feature may take on different forms Buildings Engineering drawing – building outline USGS Quad Sheet – point location City USGS Quad Sheet – Polygon of city boundary Rand McNally Map – Point representing city location Topology A collection of numeric data which clearly describes adjacency, containment, and connectivity between map features and which can be stored and manipulated by a computer Topology © Paul Bolstad, GIS Fundamentals ARC/INFO vs ArcView ARC/INFO is a topologically based hybrid system ArcView is a file based, non topological, pseudo object-oriented graphic data structure File Formats ARC/INFO Coverage ArcView Shape Geodatabase Layer AutoCAD DWG/DXF MapINFO Other The Shape File The shapefile format defines the geometry and attributes of geographically-referenced features in as many with specific file extensions that must be stored in the same project workspace They are: shp - the file that stores the feature geometry Required shx - the file that stores the index of the feature geometry Required dbf - the dBASE file that stores the attribute information of features Required sbn and sbx - the files that store the spatial index of the features Optional © ESRI, Modeling Our World © ESRI, Modeling Our World Homework Reading: A PDF document on data models Exercise: GTK 5abcd (Symbolizing features and rasters) ... GIS data models After this lecture you should be able to: Describe the primary Vector data models used in GIS and give examples Describe raster data models and give examples Describe TIN data. .. graphic data is stored in the form of discrete points, lines, or polygons © Paul Bolstad, GIS Fundamentals Structure of Vector Data There is a relationship between vector data types Each data. .. Polygons “Linked” Attribute Data Tabular Data (Attributes) © ESRI Attribute Data Information which describes an entity represented by a graphic feature Attribute Data Information about a graphic