Spatiotemporal GIS

Standard GIS: Spatial Characteristics only Implicit time is usually “now”

Spatiotemporal GIS: Adds concept of time What happened when and why? Examples: Pandemic response, traffic modeling

Stages of Spatiotemporal GIS

Stage zero: no temporal data Static printed road map

Stage one: snapshot Collection of annual road maps

Stage two: object lifelines Building construction

Stage three: events, actions processes Property registration system

Defining temporal terms

Spatiotemporal GIS requires explicit definitions of terms like “event”, “action”, and “process”

Two classification systems Mourelatos taxonomy: hierarchy of specifics

descended from a “situation” Distinction between count nouns and events, and

mass nouns and processes

Transaction and Valid time

Transaction time Time at which data was entered into database

system Can only increase

Valid time Time at which event/process occurred Can change both forwards and backwards

Bitemporal systems: use both Transaction and Valid time

Spatiotemporal GIS considerations

Timeline definition Can be continuous, rational or discrete (ticks of a

clock) Consists of both discrete instants and intervals

Data structures Standard data structures are ill-suited for temporal

data Alternatives include overlapping B-trees,

multiversion B-trees, and historical R-trees

Questions

How many stages are there in spatiotemporal GIS?

What's the difference between transaction time and valid time?

Temporal GIS and Applications

• History of temporal GIS

• Concepts

Time Geography

• Looks at time allocation with respect to constraints

• 3 types of constraint• Capability constraints• Coupling constraints• Authority constraints

Process and Events

• Applications need to handle the relationship between processes and events

• How to view processes and events

Spatio-temporal Query Language

• Query languages can be used to view spatio-temporal data

• Applications• Applications used to move objects• Applications dealing with discrete changes• Applications dealing with changing motion and

shape

Modeling with Spatial and Temporal Uncertainty

• Uses Bayesian maximum entropy

• Useful in many different professional fields