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Lecture 3: Network Data Models

Department of Geography and Urban Studies, Temple University GUS 0265/0465 Applications in GIS/Geographic Data Analysis. Lecture 3: Network Data Models. Representing and Analyzing Networks in GIS. Network : a system of linear features connected at intersections and interchanges

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Lecture 3: Network Data Models

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  1. Department of Geography and Urban Studies, Temple UniversityGUS 0265/0465Applications in GIS/Geographic Data Analysis Lecture 3: Network Data Models

  2. Representing and Analyzing Networks in GIS Network: a system of linear features connected at intersections and interchanges A network is composed of a set of nodes and a set of spanning directed links. Each link is represented by an ordered pair of nodes (i,j).

  3. An Example Network

  4. Examples of Networks

  5. Node-Node Adjacency Matrix • The rows and columns in the matrix correspond to the nodes on the network. • A non-zero element in the ith row and jth column in the matrix represents the numerical value associated with link (i, j). • A zero element in the matrix in the ith row and jth column in the matrix indicates that there exists no link going from node i to node j.

  6. Node-Node Adjacency Matrix

  7. Forward Star Representation • Links are numbered in the following order: • First links emanating from node 1 are numbered, then those from node 2, and so forth. • Links emanating from the same node are numbered in an arbitrary fashion. • Once this list of ordered links is obtained, data associated with the links are stored in single arrays sequentially.

  8. Forward Star Representation

  9. Forward Star Representation Node Pointer Table

  10. Reverse Star Representation Forward star representation facilitates accessing links by beginning nodes Reverse star representation facilitates accessing links by ending nodes Incoming links at each node are numbered sequentially

  11. Reverse Star Representation

  12. Reverse Star Representation Node Pointer Table

  13. Forward and Reverse Star Representation

  14. Network Representation in ArcInfo • Composed of Edges and Junctions • Geometric Network stores coordinates • Logical Network stores connectivity

  15. Solver: a program to perform network analysis Trace: a solver that traces along a network NetFlag: a location on a network Weights: weighting travel along an edge Network Representation in ArcInfo

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