1. Lecture 9 GIS-based Urban Modelling
9-1 Introduction
Did not take place until the late 1980s.
As a part of the GIS community’s efforts to improve the analytical capabilities of GIS.
GIS has provided modelers with new platforms for data management and visualization.
Diffusion of GIS in society make models more transparent and results to a large group of users.
2018/11/23
Jun Liang, UNC

2. 9-2 GIS-based Urban modelling: Current Practices
Four major approaches:
1. Embedding GIS-like functionalities into urban modelling packages.
Adopted primarily by urban modellers and spatial statisticians.
Downside? (1) Data management, visualization. (2) Developed by individual researchers.
2018/11/23
Jun Liang, UNC

3. 9-2 GIS-based Urban modelling: Current Practices (Cont.)
2. Embedding urban modelling into GIS by software vendors.
- GIS software also has begun to include limited urban related functions, models, etc.
Examples for ArcGIS:
Utility Network analyst, Geostatistical analyst, Survey Analyst, Tracking Analyst, etc.
2018/11/23
Jun Liang, UNC

4. 9-2 GIS-based Urban modelling: Current Practices (Cont.)
3. Loose coupling.
Urban modelling and GIS are integrated, via data exchange using either ASCIII or binary data format,
among several different software packages without a common user interface.
2018/11/23
Jun Liang, UNC

5. 9-2 GIS-based Urban modelling: Current Practices (Cont.)
Advantages:
Redundant programming can be avoided.
Easy to be modified.
Less coding. This approach may be the most realistic method for most GIS users to conduct modelling work..
Drawbacks:
Most time, no main GUI.
Data shuffling and conversion between different packages can be tedious and error prone.
2018/11/23
Jun Liang, UNC

6. 9-2 GIS-based Urban modelling: Current Practices (Cont.)
4. Tight coupling.
This approach embeds certain urban models with a commercial GIS software package via either GIS macro or
conventional programming. Sui claimed – “…Such languages are seldom powerful enough to implement sophisticated models,…”
2018/11/23
Jun Liang, UNC

7. 9-2 GIS-based Urban modelling: Current Practices (Cont.)
Allow user-developed modelling libraries or routines to be called within the normal pull-down menu of a particular software package.
Allow user-developed tools to be accessed by other users (standard tools can be shared).
Requires a well-defined interface to the data structures held by the GIS.
Functions/objects/classes are growing very fast, and may need significant time in programming.
2018/11/23
Jun Liang, UNC

8. 9-2 GIS-based Urban modelling: Current Practices (Cont.)
Two other features of the recent GIS-based urban modelling efforts are worth noting:
The development and introduction of a series of new concepts and techniques in urban modelling - cellular automata, fractals, neural networks, parallel processing, and genetic algorithms, etc.
The rise of urban modelling applications in the private sector, relating to marketing and geodemographic analysis.
2018/11/23
Jun Liang, UNC

9. Jun Liang, Geography @ UNC
9-3 Existing Problems
Problems of the urban models
Land use policy decision support
Interaction modeling (gravity, network, etc.)
Simulation modeling (urban sprawl, crime pattern, etc.)
Problems of GIS
Open source GIS (GRASS) has more research capabilities, no cost to share.
Commercial GIS software is more user friendly, good support, and more users.
2018/11/23
Jun Liang, UNC

10. 9-3 Existing Problems (Cont.)
Problems of GIS (cont.)
Map layer representation scheme is not only temporally fixed but is also incapable of handling overlapping features.(Sui)
2018/11/23
Jun Liang, UNC