Lecture 08: Data Representation (VI) Topics 3. Data Models 3.3 Spatial data models 3.3.2 Vector Data Models II Readings on the topics Chapter 8 in the text, pp. 184-186 Chapter 6 in Aronoff’s (1993), pp. 174-176 Other readings Chapter 3 in Bonham-Carter’s (1994), pp. 71-78

Lecture 07: Data Representation (V) 3. 3 Spatial Data Models: 3.3.2 Vector data models II: D. Types of Vector Data Models 1) Spaghetti (Entity by Entity) Models 2) Topological Data Models (1) Definition (The topological data model figure) (2) Versions of Topological Models a) GBF/DIME data model (US Census Bureau) (The GBF/DIME figure) b) DLG (USGS) (The DLG Figure)

(3) Evaluation of Topological Data Models: (a) Topologic is explicitly encoded (b) Special instances can be encoded (c) Very compact (D) Complex, difficult to construct

Questions 1. What is a topologic data model? What is a topological triangle? 2. What are the advantages and disadvantages of a topological data model? 3. You should be able to code a simple map using a topological model with the needed topology given in a topological triangle. 4. Describe the DIME data model of US. Census Bureau and describe the DLG data model from USGS.