GIS Modeling

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GIS Modeling

• GIS Topics and Applications

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5 Ms of GIS

• Mapping
• Measurement
• Monitoring
• Modeling
• Management

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Geoprocessing

• When we perform geoprocessing tasks on our data,
  we are developing the components of a GIS model.
• We perform geoprocessing every time we
• Use a tool interactively in ArcMap
• Use tools from ArcToolbox
• Execute commands using the command line
• Connect tools in ModelBuilder
• Use functions in a script (like Python)

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Static and Dynamic

• Static modeling is the series of steps required
  to achieve some final result.
• Available land for development of a nursery
• Siting of cell towers
• Dynamic modeling is performed in a similar
  fashion, but has additional parameters requiring
  several iterations of the model.
• Disease outbreak modeling
• Real-time traffic analysis
• Spread of wildfires, heavy rain, etc.

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Why Model?

• Developing a model for a GIS analysis allows for
  repeat testing of a hypothesis using different
  data.
• The model can be coded into a GIS application, so
  that the steps are performed automatically.
• Easier reproduction of results.
• Simplification of workflow.
• Informs the computer how to conduct a series of
  steps that would be impractical for you to do
  manually.

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Reproducibility

• In performing an analysis, you must have your
  workflow clearly defined.
• This ensures that you are performing the steps in
  the correct order using the appropriate tools.
• Missteps are easy, especially when there can be
  hours of computer processing between steps.
• The GIS model can be exported as a graphic
  flowchart or a modeling data structure.

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Workflow Efficiency

• There are many repetitive steps you will take in
  your daily workflow.
• Streamlining the process saves you time.
• If you always start working in a File Geodatabase
  with specific resolution and projection
  information, a model for generating your
  specialized GDB can be created.

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Human Inefficiency

• You physically cannot perform the steps as fast
  as GIS can produce the results.
• Certain steps, such as iteration through a
  feature set would be prohibitively time
  consuming.
• You must perform the same steps 21 times to clip
  data to each individual NJ county.
• Rail use analysis 200 stations
• Minimize the amount of time spent babysitting
  GIS to perform complex analyses.

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How do we model?

• ArcGIS has a drag-and-drop interface to
  ArcToolbox called ModelBuilder allowing you to
  develop a flow chart of your GIS workflow.
• This flowchart is then run step by step to
  perform your analysis.
• ArcGIS allows for custom scripting that can be
  added to ArcToolbox, introducing greater
  functionality.
• Custom export scripts, specialized versions of
  existing tools, develop tools not available in
  ArcToolbox.

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ModelBuilder
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Introduction to ModelBuilder

• Over the past semester, we've performed several
  geoprocessing tasks
• We have used geoprocessing tools in sequence to
  analyze GIS data
• ArcGIS allows you to link tools together to
  create a workflow

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Homework Flashbacks

• You have a set of points, that you want to clip
  to a county, then find the count of points that
  fall within each municipality
• You have a statewide layer you want to clip to a
  specific feature, then dissolve
• ModelBuilder will allow you to select features,
  perform tasks like clip, spatial join, merge, etc

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Inside ArcToolbox
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Inside ArcToolbox

• Models and Scripts are added to custom toolboxes
  you create in ArcToolbox.

Toolbox
Toolset
Script
Model
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Creating a New Toolbox

• Creating your own Toolbox is not just for
  organizational purposes. It allows you to share
  your models with others.
• If you will be sharing your model and using
  relative addresses, you need to plan the folder
  location of your New Toolbox carefully.
• Default location for a New Toolbox created inside
  ArcToolbox is C\Documents and Settings\ltuser
  profilegt\Application Data\ESRI\ArcToolbox\My
  Toolboxes.
• Create a new Toolbox by right clicking in
  ArcCatalog and selecting New Toolbox.

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How ModelBuilder Works

• Drag layers you want to participate into the
  model
• Drag tools you want to use into the model
• Output layers, tables, objects shown in green
• Connect the features using arrows
• Order matters to certain tools (Clip)

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Revisiting Assignment 3

• In this assignment, we selected the
  municipalities in Gloucester County
• We then selected the KCS within the Gloucester
  County municipalities
• Finally, we performed a spatial join on the two
  layers to find a count of KCS within each of the
  municipalities

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Getting Started

• Let's make a new Toolbox to store our models
• Make a new model inside the Toolbox
• Edit the model

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Drag and Drop Interface
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Order Matters
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Order Matters
1
2
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Order Matters
2
1
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Final Model
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Multiple workflows in one Model
reclassed road distance
non-floodprone layer
residential and wetlands plus buffer
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Additional Functionality

• The Model can be expanded further, with more data
  and tools
• The Model can be exported into a scripting
  language, allowing for greater modeling
  capabilities.

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Additional Functionality

• Python is the default (and recommended) scripting
  language for ModelBuilder
• Cursor-based analysis For each individual
  feature in a layer, perform some analysis
• For each "vacant" polygon, is it surrounded by
  environmentally sensitive features?
• Count each feature's vertices, rings
• Internet access automatically download data,
  then analyze

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Going Further

• A ModelBuilder OverviewAvailable on ESRI's
  support page
• Getting Started Writing Geoprocessing
  ScriptsAvailable on ESRI's support page
• Dive Into Pythonhttp//www.diveintopython.org/
• Learning Python, 3rd Editionhttp//www.oreilly.co
  m/catalog/9780596513986/