GIS for Environmental Modeling

Geog 479/559 Spring 2009	Tu Th 2:00 - 3:20pm
Instructor: Ling Bian Office: 120 Wilkeson Quad Office Hours: Tu Th 12:30-1:30pm	322 Fillmore Lab: T 12:30-1:50pm or W 11am-12:20pm, Wilkeson 145 TA: Liang Mao

GIS Modeling

1. GIS

G: maps

I: spreadsheets

S: the system that puts the maps and spreadsheets together

Formal definitions of GIS

A GIS is a computer-based system that provides for the collection, storage, analysis., and display of geo-referenced data
A decision support system involving the integration of spatially referenced data in a problem solving environment

    GIS and GIS
        Geographic information systems - it refers to software, hardware and it is used as a tool to support other research
        GIScience - Geographic information science

    Components in GIS
        Spatial entities
        Spatial locations
        Attributes
        Topology

    Spatial Entities
           Real world entities
           Spatial entities - points, lines, polygons, grids, volumes

    Spatial locations
            Specified with reference to a common coordinate system
            Geographic coordinate system (latitude and longitude)
            UTM (Universal transverse Mercator)
            State Plane

    Attributes - variables, properties, etc.
            Four types of attribute values
            nominal (river, grass, etc.)
            ordinal (high, medium, low)
            interval (10^oC, 20^oC)
            ratio (2.19, -96.57)

Topology (relationship between geographic features (points, lines, polygons)
adjacency, containment, connectivity, etc.

GIS data models
vector and raster

2. GIS Modeling
        1) Conceptualizing the Model – Project Design
        Identify the goal first - What is the problem
                 e.g., where to put ATM machines
                 e.g., where are the most appropriate places to cut old trees in a state park

        Identify the factors that affect the solution
                 For the locations of ATM machines
                 factor 1
                 factor 2
                 factor 3

                 For cutting old trees in a state park
                 F1
                 F2
                 F3

        2) Formulating the Model – Methodology Design
        Find the spatial data for each factor
        Use surrogate data if direct data are not available
                 For the locations of ATM machines
                 F1: data =
                 F2: date =
                 F3: date =

        Identify spatial operators
                 e.g., overlay, buffering
                 neighborhood analysis, topographic analysis, spread function, stream function, viewshed analysis
                 network analysis, etc.

For the location of the wastewater treatment plant
Operator 1, 2, …

        3) Implementing the Model – Methodology Implementation
        Collect the data
        Run spatial operations
        Map the results

4) Calibrating, Validating, and Refining Models
The output is nothing more than a pretty picture without acceptability assessment

                Go to field or use actual decision records to provide evidence
                Use aerial photo or satellite images as surrogate evidence
                Set a small set of data aside and use it later to validate the model results

Make sure all variables are significant for the model
Make sure the model is appropriate

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