Lecture 07: Data Representation (V) Topics 3. Data Models 3.3 Spatial data models 3.3.1 Raster Data Models 3.3.2 Vector Data Models Readings on the topics Chapter 8 in the text, pp. 183-184 Chapter 6 in Aronoff’s (1993), pp. 172-177 Other readings Chapter 3 in Bonham-Carter’s (1994), pp. 68-71 Chapter 3 in Burrough and McDonnell (1998), pp. 57-64

Lecture 07: Data Representation (V) 3. 3 Spatial Data Models: 3.3.2 Vector data models: A. Vector representation The basic concept (The Vector Representation Figure) The representation of point, linear and area features (The point, line, area in vector figure)

B. Terminology Vertex Node Arc Polygon Label point C. Spatial Topology Spatial relationships of the basic geometric elements

D. Types of models 1) Entity by Entity (Spaghetti) Model a) definition: b) Versions of spaghetti models: (1) Simple lists (The simple lists figure) (2) Point directory (The point directory figure) c) A comparison of spaghetti models (The Spaghetti comparison figure)

E. Summary: (1) Geographic features are treated as individual objects The spatial boundary is explicitly coded (2) No relationships among objects Spatial topology among features are not explicitly coded

Questions 1. How does a vector data model represent spatial data? How does it represent a point feature, a linear feature, and an area feature? 2. What are the advantages and disadvantages of the vector data model? 3. What is an arc and what is a node? Can any point be a node? what is the difference between arc and a polyline (a line made of multiple straight segments)? 4. How are the three basic geometric elements are used to capture spatial topology in a topological data model? 5. What is the main difference the simple list data model and the point directory data model? Why don’t we consider them to be topological data models?