Space-Time Analytics of Tracks for the Understanding of Patterns of Life - Space-Time Integration in Geography and GIScience - page 371

be useful elements to decipher movement patterns for individuals or collectives.
Structures are proximity, connectivity, ordering, or relationships in space, time,
and semantics. Here, semantics simply refers to the element's characteristics and
meanings of interest. Kinship, for example, is a semantic relationship, and so
is management in an operation and participation in a social network or orga-
nized/unorganized activity. With this emphasis, space-time analytics focuses on
what space-time elements and structures pertain to the research questions of interest
and how to elicit these elements and structures from complex data.

20.4 A Conceptual Framework for Space-Time

Analytics of Tracks

The conceptual framework of space-time analytics of tracks proposed below,
extending the conceptual frameworks of time geography and trajectory analysis,
aims to discern space-time patterns of multiple tracks repetitively taken by given
individuals, and from the space-time patterns to interpret spatial patterns of life for
individuals, their potential interactions, and the spatial patterns of social pulses in
the related population. Clarification of terminology is important to communicate
concepts precisely. While many terms seem have inconsistent meanings in previous
studies, great attention is given to avoid incompatibility of the terms used in the
proposed conceptual framework:

￿ Path : the actual route that one took. A path usually follows transportation

networks or existing pathways except when travelling in an open space such as a
yard, plaza, air or sea.

￿ Track : the line formed by connected observed locations. A track is based on

observations taken by GPS points, geo-tagged media, or journey narratives. With
a track we know temporally ordered locations visited by a mobile object, but we
don't know exactly the path that the object took to travel from one location to the
next.

￿ Trajectory : the expected route that one took from one location to the next.

A trajectory is a movement estimate based on space-time continuum and space-
time constraints. For a car and two consecutive observations of its locations,
its trajectory is expected to follow one of the road options between the two
locations, except for accidents such as driving into a lake. With a surveillance
video, identified individuals are assumed to move within a space-time continuum.
Spatial and temporal interpolation methods can be used to estimate the possible
trajectories between two known locations.

￿ Stops : locations on a track where a mobile object stays over a length of time

beyond a specified duration. A car makes stops at traffic lights, a person stops
by a convenience store, and a train stops at a city station. A specified duration
may be 30 s, 10 min, an hour, or a week, etc. depending upon what meaningful
information may be in the problem domain of interest.