GIS Modeling


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GIS Modeling

  1. 1. GIS Modeling<br />GIS Topics and Applications<br />
  2. 2. 5 Ms of GIS<br />Mapping<br />Measurement<br />Monitoring<br />Modeling<br />Management<br />
  3. 3. Geoprocessing<br />When we perform geoprocessing tasks on our data, we are developing the components of a GIS model.<br />We perform geoprocessing every time we:<br />Use a tool interactively in ArcMap<br />Use tools from ArcToolbox<br />Execute commands using the command line<br />Connect tools in ModelBuilder<br />Use functions in a script (like Python)<br />
  4. 4. Static and Dynamic<br /><ul><li>Static modeling is the series of steps required to achieve some final result.
  5. 5. Available land for development of a nursery
  6. 6. Siting of cell towers
  7. 7. Dynamic modeling is performed in a similar fashion, but has additional parameters requiring several iterations of the model.
  8. 8. Disease outbreak modeling
  9. 9. Real-time traffic analysis
  10. 10. Spread of wildfires, heavy rain, etc.</li></li></ul><li>Why Model?<br /><ul><li>Developing a model for a GIS analysis allows for repeat testing of a hypothesis using different data.
  11. 11. The model can be coded into a GIS application, so that the steps are performed automatically.
  12. 12. Easier reproduction of results.
  13. 13. Simplification of workflow.
  14. 14. Informs the computer how to conduct a series of steps that would be impractical for you to do manually.</li></li></ul><li>Reproducibility<br />In performing an analysis, you must have your workflow clearly defined.<br />This ensures that you are performing the steps in the correct order using the appropriate tools.<br />Missteps are easy, especially when there can be hours of computer processing between steps.<br />The GIS model can be exported as a graphic flowchart or a modeling data structure.<br />
  15. 15. Workflow Efficiency<br />There are many repetitive steps you will take in your daily workflow.<br />Streamlining the process saves you time.<br />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.<br />
  16. 16. Human Inefficiency<br />You physically cannot perform the steps as fast as GIS can produce the results.<br />Certain steps, such as iteration through a feature set would be prohibitively time consuming.<br />You must perform the same steps 21 times to clip data to each individual NJ county.<br />Rail use analysis: 200+ stations<br />Minimize the amount of time spent “babysitting” GIS to perform complex analyses. <br />
  17. 17. How do we model?<br />ArcGIS has a drag-and-drop interface to ArcToolbox called ModelBuilder allowing you to develop a flow chart of your GIS workflow.<br />This flowchart is then run step by step to perform your analysis.<br />ArcGIS allows for custom scripting that can be added to ArcToolbox, introducing greater functionality.<br />Custom export scripts, specialized versions of existing tools, develop tools not available in ArcToolbox.<br />
  18. 18. ModelBuilder<br />
  19. 19. Introduction to ModelBuilder<br />Throughout your GIS education, you've performed several geoprocessing tasks<br />We have used geoprocessing tools in sequence to analyze GIS data<br />ArcGIS allows you to link tools together to create a workflow<br />
  20. 20. Inside ArcToolbox<br />
  21. 21. Inside ArcToolbox<br /><ul><li>Models and Scripts are added to custom toolboxes you create in ArcToolbox.</li></ul>Toolbox<br />Toolset<br />Script<br />Model<br />
  22. 22. Creating a New Toolbox<br />Creating your own Toolbox is not just for organizational purposes. It allows you to share your models with others.<br />If you will be sharing your model and using relative addresses, you need to plan the folder location of your New Toolbox carefully.<br />Default location for a New Toolbox created inside ArcToolbox is: C:Users<user profile>Application DataESRIArcToolboxMy Toolboxes.<br />Create a new Toolbox by right clicking in ArcCatalog and selecting New Toolbox.<br />
  23. 23. How ModelBuilder Works<br />Drag layers you want to participate into the model<br />Drag tools you want to use into the model<br />Output layers, tables, objects shown in green<br />Connect the features using arrows<br />Order matters to certain tools (Clip)<br />
  24. 24. Determining Points Within<br />Searching for a count by municipality of all the contaminated sites (KCSL) in Gloucester County<br />Select just Gloucester County municipalities, then all KCSL within the selected area<br />Then perform a spatial join on the two layers to find a count of KCS points within each of the municipalities<br />
  25. 25. Getting Started<br />Let's make a new Toolbox to store our models<br />Make a new model inside the Toolbox<br />Edit the model<br />
  26. 26. Drag and Drop Interface<br />
  27. 27. Order Matters<br />
  28. 28. Order Matters<br /> 1<br /> 2<br />
  29. 29. Order Matters<br /> 2<br /> 1<br />
  30. 30. Final Model<br />
  31. 31. Multiple workflows in one Model<br />reclassed road distance<br />non-floodprone layer<br />residential and wetlands plus buffer<br />
  32. 32. Models used in the Workplace: NJ DEP<br />
  33. 33. Additional Functionality<br /><ul><li>The Model can be expanded further, with more data and tools
  34. 34. The Model can be exported into a scripting language, allowing for greater modeling capabilities. </li></li></ul><li>Additional Functionality<br />Python is the default (and recommended) scripting language for ModelBuilder<br />Cursor-based analysis: For each individual feature in a layer, perform some analysis<br />For each "vacant" polygon, is it surrounded by environmentally sensitive features?<br />Count each feature's vertices, rings<br />Internet access: automatically download data, then analyze<br />
  35. 35. Going Further<br /><ul><li>A ModelBuilder OverviewAvailable on ESRI's support page
  36. 36. Getting Started Writing Geoprocessing ScriptsAvailable on ESRI's support page
  37. 37. Dive Into Python
  38. 38. Learning Python, 3rd Edition</li>