Modeling of Flows in GIS

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Modeling of Flows in GIS



.Michael F. Goodchild Alan Glennon



Department of Geography



University of
California, Santa Barbara 8 December 2004
Hot Creek, California / photo Glennon
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Data modeling issues

• Mixtures of primitive elements
• the lower Colorado
• Linear features with transverse detail
• the coastal zone, railroads
• Fields of objects
• viewsheds, watersheds
• Interactions over space
• attributes of pairs of objects
• association classes

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• Dynamics
• moving objects
• tracking vehicles as points
• objects that change shape
• imaging vehicles
• objects with changing internal structure
• severe storms

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Peggy Agouris (Maine) Tracking vehicles through
feature extraction from imaging camera
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Helix representation
Spine expresses spatio-temporal 3-D movement of
the center of mass.
Prongs express expansion or collapse of the
objects outline
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May Yuan, University of Oklahoma
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Hurricane Frances
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Hurricane helixes
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• Flows
• A common type of data in
• hydrology, atmospheric science
• social science
• Channeled
• migration
• streamflow
• Unchanneled
• overland flow
• ocean currents

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• Outline
• Purpose
• Model Development
• Implementation
• Future Work

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Purpose
Broader Context

• Formalize the concept of flow in geographic
  space.
• Create a framework to store flow information in
  GIS.
• Create tools to access flow information in GIS
  for visualization and analysis.

• Allow sharing / provide common information
  format for flows within GIS.
• The way flow data is organized influences the
  analyses that can be conducted.
• Ontology of flow ? a better understanding /
  characterization of geographic dynamics.
• Expand the capabilities of GIS.

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Toblers Flow Mapper Program
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www.csiss.org under Spatial Tools
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• Spatial Interaction Table Human Migration
• Minards Map of Napoleons March to Moscow
• Karst Watershed Flow Routes

Use Cases
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Source The Napoleon Foundation
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Source U.S. Census Bureau, Census 2000
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Source Tufte, 2001
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Cave Survey Book / photo Glennon
Mill Hole, Kentucky / photo Jasper
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• Tests of a data model
• provides "slots" to store everything relevant to
  the use case
• identifies the classes present on the map
• points, lines, areas, annotation
• specialization of lines as flows
• allows the map to be recreated from the data
  model

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MINARD NAPOLEON MAP
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INTERACTION

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KARST FLOW ROUTES
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ORIGINAL USE CASE MODELS
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Generic Flow Model



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Generic Flow Model



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Use Case Human Migration



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Use Case Minard Map



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Use Case Karst Watershed Flow Routes



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Toblers Flow Mapper
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Flow Mapper

• Cartography handled semi-automatically
  (front-loaded cartography).
• Task-specific GIS user is limited to the
  softwares existing analytical tools (customized
  queries are not possible).
• Creates SVG output.

• Stand-alone, single-function software. Current
  version 1.1.
• Represents flows from an n x n interaction
  matrix and set of point coordinates (text files
  as inputs).
• Depicts two-way, net, and gross flows.
• Rapid calculation and visualization.

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Flow Data Model Tools

• Set of ArcGIS macros to allow import, export,
  and visualization of flows using the Flow Data
  Model. Current version is beta, v0.69b.
• Coded and designed in VBA.
• Incorporates capabilities of Flow Mapper into
  ArcGIS, allowing flexibility of ArcGIS
  generalized spatial analysis platform.
• Calculates and represents gross, net, and
  two-way flows from the Flow Data Model.

• User responsible for cartographic output
  relies on ArcGIS platform (end-loaded
  cartography).
• Interaction matrix import process is similar to
  Flow Mapper (requiring text files as input).
• Tasks are modularized to increase flexibility
  in data inputs and analysis.
• ArcGIS file types as outputs.

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Ongoing Future Work, and Wishlist

• Integrate with specialized data models
  (ArcHydro, UNETRANS, etc)
• Finish data extraction functionality
• Finish FlowMapper importer
• Need to move to industrial strength code
• Need extensions to ArcGIS cartographic tools

• Generalize to the rectangular case (origins and
  destinations distinct)
• Flow on polyline
• Integrate with polyline m (flow as function of
  m)
• Within-feature flows
• Analysis routines
• Continuous (unchanneled) case (flow as a vector
  field)
• Animation of flows

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Alan in Coal Trace Cave, KY / photo G. Berdeaux
Alan in Talley Cave, KY / photo C. Groves
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Acknowledgments
Waldo Tobler, University of California, Santa
Barbara Jack Dangermond and Rhonda Pfaff,
ESRI Tom Cova, University of Utah May Yuan,
University of Oklahoma
Skogafoss, Iceland / photo Glennon