geoprocessing ii. esf laboratory for applied gis 2 just what is geoprocessing? geoprocessing is used...

Geoprocessing II

esf Laboratory for Applied GIS

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Just what is Geoprocessing?

• Geoprocessing is used by everyone that uses ArcGIS. Whether you're a new user or an old pro, geoprocessing will become an essential part of your day-to-day work with ArcGIS. (esri)

• So we have to emphasize it!

esf Laboratory for Applied GIS

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Two flavors of Geoprocessing

• Process modeling– What we have been talking about– Is a model of a physical process– Can be static or dynamic – iteration

• Simulation– Explicitly model a process in time

esf Laboratory for Applied GIS

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Simulation

• Model a phenomenon in time– Example: Forest fire growth

• Create realizations of a phenomenon as it moves through space and time with changing variables (fuel load, weather)

• Can be Deterministic or Stochastic

esf Laboratory for Applied GIS

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Simulations

• Deterministic– Model with well understood rules

• Stochastic– Have a component of randomness

• Don’t fully understand the rules• Error in input data (very common)• Error in model parameters• Interactions between layers (propagation

of error)

esf Laboratory for Applied GIS

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More?

• This gets pretty complex and the online help system has some very good discussions on the subject.

• Got to– bhelp.esri.com/arcgisdesktop/9.2/inde

x.cfm?id=923&pid=921&topicname=General_concepts_of_modeling_through_simulations

esf Laboratory for Applied GIS

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Its Purpose

• Almost all uses of GIS involve repetition

• The automation of geospatial tasks– Saves time– Provides documentation– Share methods

• These methods are called Workflows

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Workflows

• A Workflow is a collection of Steps and data that define the paths that can be taken to complete a task. ...

• So when presented with a problem with a set of criteria that must be met

• You generate a workflow

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A Problem

• Task is to find tax parcels that could possibly be used for a nature center– Are at least 20 acres in size– Have both forest and Agricultural lands– Are within 6 miles of each of the

town’s schools– Contain a stream or river (or be on a

river bank)– Preferable the parcel should be owned

by the town or the state

esf Laboratory for Applied GIS

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And the derived workflow is…

1. What tools would be used for each of the criteria?

2. In what order would these sub-tasks be undertaken?

3. Graphically…

esf Laboratory for Applied GIS

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Schematically

Data DataProcess

Data

Process

Or by text list

esf Laboratory for Applied GIS

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A Problem

• Task is to find tax parcels that could possibly be used for a nature center– Are at least 20 acres in size– Have both forest and Agricultural lands– Are within 6 miles of each of the

town’s schools– Contain a stream or river (or be on a

river bank)– Preferable the parcel should be owned

by the town or the state