TEMPORAL GIS

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TEMPORAL GIS
Dr Francisco EscobarDept of Geospatial
ScienceRMIT University francisco.escobar_at_rmit.edu
.au
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Overview

• Introduction
• About time
• Temporal dimension and GIS
• Time-based GIS models
• Time Geography and spatio-temporal regions
• Approaches for the integration of TG with GIS

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Introduction

• Temporal variations are crucial in most GIS
  applications
• Versioning
• Dynamic phenomena
• Dynamic processes
• GIS search where? what? increasingly when?

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Time is always present in Geographic DataTime
makes Cartographydifferent to Geometry
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About time

• Scarce resource but endless
• Non stackable
• Non extendible
• Same pace for everyone
• Intersections on time related phenomena (what)
  that merge in a particular place (where) at a
  particular moment (when)

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Temporal dimensions and GIS

• Understanding and digitising time
• Conceptualisation and modelling
• What kind of time?
• Lineal or cyclical time?
• Calendar and watches or subjective time?
• Absolute or relative time?

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Temporal dimensions and GIS
Understanding and digitising time

• Should we register the changes or the successive
  states?
• What phenomena are considered relevant in a
  continuous time line?
• How to represent gradual changes?
• What distortions and imprecision are acceptable?

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Temporal dimensions and GIS
Understanding and digitising time

• Three different approaches
• Time as a Z attribute DEM
• Region-to-entity layers.
• Monitoring changes implies comparisons between
  layers
• Space-time entity agents
• The interest resides on entities behaviour

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Temporal dimensions and GIS

• Temporal registry of territorial changes
• At least implicitly all cartographic
  representation includes time
• A snapshot is not enough. To apprehend the
  dynamics interpolation is needed
• GIS made it possible to store historic records
  TGIS. But unable to answer questions on dynamism

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Temporal dimensions and GIS

• Temporal registry of territorial changes
• Langrans 4 ways to understand and represent time
  in GIS
• Tetra-dimensional or hyper cube. Continuous
• Snapshots. Discrete. The only one available
• Only changes registered. Only applied to raster
• Spatio-temporal composition. State-map.

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Tetra-dimensional or hypercube.Continuous
time-space
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Temporal dimensions and GIS

• Spatio-temporal representation of autonomous
  entities agents
• System situated within and a part of an
  environment that senses that environment and acts
  on it, over time, in pursuit of its own agenda
  and so as to effect what it senses in the future

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Unsolved problems

• Temporal data models
• Commercial GIS still in the slice stage
• Temporal resolution and scale
• Storage and longevity of temporal data
• Changes distribution and updates without
  compromising data integrity

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Spatio-temporal accessibility and GIS

• Another way to consider time in GIS consists on
  accessibility analysis
• Location-allocation models
• Median Scheduling Problem

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Time Budgets and Constraints
time
distance
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Spatio-temporal accessibility and GIS

• Potential Path Space
• Potential Path Area

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Minutes from red and green nodes we can spend at
different locations if departing from A and
arriving to B 120 minutes later
b
a
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Limited accessibility with iso-chrones
(OSullivan et al, 2000)
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Activity Diaries in GIS
2) Standardization and encoding ASCII files
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Data sources

• Field work GPS/diaries
• Existing databases
• RACV
• Public transport timetables
• Emergency Services

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Spatio-temporal accessibility and GIS

• http//divcom.otago.ac.nz/SIRC/GeoComp/GeoComp98/6
  8/gc_68a.htm

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Time-Geography and the Spatio-Temporal Region

• Director presentation

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Approaches for the integration of TG with GIS

• Accessibility
• School of Alcalá, Spain, Maria Salado
• School of Auckland, NZ, Otto Huisman
• Lifelines for health events
• NCGIA, David Mark
• Lifelines for individuals and events
• RMIT, Francisco Escobar

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Potential Accessibility
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Business hours within a distance
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Dynamic segmentation

• It has the potential to provide the means for a
  time-GIS integration in a continuous manner
• Analogies with lifelines

In dynamic segmentation each element presents
different attributes in each of its different
sectors but it is kept as an undivided unit
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• Temporal
• GIS

Time Geography
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http//www.as.rmit.edu.au/courses/geospatial/timed
istance/
MM applied to TG and GIS
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Types of animated mapping

• Types of changes (1)
• Shape

(Hayward, 1984)
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• Types of changes (2)
• Location

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t2
t1

• Types of changes (3)
• Rate

t2
t1
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• Types of changes (4)
• Structure or texture

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• Types of changes (5)
• Perspective (ArcView 3D Scene)

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• Types of changes (6)
• Colour

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• Types of changes (7)
• Size

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• Types of changes (9)
• Scene

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• Types of changes (10)
• Shot

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• Types of changes (11)
• Theme

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Potential

• Utilisation of existing databases
• Time and space applications
• LBS
• Criminology
• Service planning
• Marketing

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Issues

• Privacy
• Static nature of GIS
• Limitations in multimedia software
• Data size

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The future