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Lecture Five

Modelling Processes and ArcGIS Model Builder

Geographic Information Systems GEOG4340 2013 winter

Cheng. Q. , Earth and Space Science and Engineering, qiuming@yorku.ca

Link to the An overview of Model builderhttp://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=An_overview_of_ModelBuilder

Combine Vector Layers (Overlay Operation)

Layer

Operator

Operator

Layer A

Layer B

Layer C

Site for Wastewater Treatment Plant

Application and Vector-based AnalysisModel of Processes

BufferRiver

Areas

Land

R_BufferOverlay Intersect

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A General Spatial Modeling Processes

•Stating the problem

•Breaking the problem down

•Exploring input datasets

•Determining analysis processes

•Verifying the model’s result

•Implementing the result and reporting

Link to the An overview of Model builderhttp://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=An_overview_of_ModelBuilder

What is a model?

A representation of reality (Real world)

ØProcess modele.g., soil erosion zoning, crop yield mapping, nonpoint source pollution mapping in watersheds

ØSuitability modelFinding a suitable location for a factory or department storeFinding suitable location for new business, school, landfill, emergency evacuation site, etc.

ModelBuilder is an application in which youn create, n edit, and nmanage models.

Link to the An overview of Model builderhttp://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=An_overview_of_ModelBuilder

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Why Model Building?

n Data analysis is the most important part of any GIS

application

n Simple GIS analysis Methodology can be solved

using simple techniques, such as just making a map

n Sometimes, it become more complex, involving

models that represent the real world by combining

several data layers and processes

n Model building can solve complex problems

involving GIS

Advantages of a ModelBuilder in GIS

n Design a modeln Automate the geoprocessing workflown Share geoprocessing knowledgen Record and document methodology n Add complexity as needed n Implement a modeln Create a model containing methods & procedures

to be shared with othersn Show the process used to create output (flow

diagrams)n In ModelBuilder, models are represented as flow

charts with different symbols

ModelBuilder window: where you edit, test and run models

AutoLayout Full

Extent

Zoom In

Zoomout Continuous

Zoom

Navigate

Select

Add Connection

Run

Modeling Process:tool, parameters (variables)

A Conceptual overview of a Model

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An Example of a ModelThere are two types of model elements:

Tools Variables

Not all parameters have been supplied for the tool to run.

All parameters have been supplied.

There are two types of variables: Data: Reference data on disk or in an in-memory layer

Values: Everything else, such as numbers, strings

Project data is data that you add to the modelMaps and Tables

Values that are input to a toolFor example, the buffer distance input

The ModelBuilder Interface

n Model elements have 3 statesn Not ready to run (parameters aren’t defined)

n Ready to run (all elements are colored)

n Already run (elements are colored and shaded)

Input tool output

Usually referred to as Derived Data

Start building your model!

n First, plan what you want to donWhat data will you need?nWhat processes will you run on each dataset?

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List of ToolboxSet of Tools

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Model of Processes for finding Distance from rec. facilities

BufferRecreational Site

Distance toRec. Site

Rec. SiteBuffer

Reclassify

Model of Processes for finding Distance beyond existing schools

BufferSchools

Distance toSchool

SchoolBuffer

Reclassify

Model of Processes for finding Relative flat area

SlopeElevation

Slope Classes

Slope Map

Reclassify

Model of Processes for finding Suitable landuse type

LanduseMap

LanduseClassesReclassify

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Model of Processes for combining Diverse maps

Landuse

Suitability Map

Calculator

Slope

Dist. Rec. Site

Dist. School

Examples for Table