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