Graphics Reference
In-Depth Information
Spatial Transaction Analysis
Dynamicspatialnetworkspresentauniquechallenge.Whenspatiallocation
is an important part of the story, options for expressing time visually are
limited. Not only do transactions occur between entities in the network over
time, entities themselves move. For example, courier services may track
their vehicles by GPS to manage routing and delivery, and opportunities for
package transfer may occur if routes cross at the same time.
When nodes are in motion over the course of a time span being analyzed,
the most natural way to visualize it is to draw a line through their path,
formingatrail.
Figure15-15
showsasimpleexampleoftherouteoftwotaxis
in the San Francisco Bay Area using this technique. One of the limitations
of this approach, however, is that time is not actually a visible dimension.
Sequences are visible, but not
when
things happen or the rate at which they
happen. For example, you cannot see here when the taxis started and ended
their routes,howfasttheyweredriving, orhowlongtheystoppedinanyone
place.
