Database Reference
In-Depth Information
Figure 12.3 One day's record of traffic over France. The color gradient from green to blue
represents the ascending altitude of aircraft (green being the lowest and blue the highest
altitude). The French coastline is apparent here in terms of pleasure flights by light aircraft
and the straight blue lines represent high altitude flight routes. A user interface shows the
data set fields and the defined visual configuration. (See color plate.)
12.4.4 Trajectory Manipulation
We have implemented a simple and efficient direct manipulation technique:
trajectory brush, pick, and drop. The user selects a subset of the data set by
means of a brushing technique. Brushing is an interaction that allows the user to
“brush” graphical entities, using a size-configurable or shape-configurable area
controlled by the mouse pointer. Each trajectory touched by this area is selected,
and becomes gray. The selection can be modified by further brush strokes, or
by removing parts of it with brush strokes in the “erase” mode. The display
shows a brush trail, so that the user can see and remember more easily how the
selection was made. The combination of fast switching between the add/erase
mode, trajectory visualization, rapid size-setting, and cursor-centered zooming
allows for fast and incremental selection.
Then the user can pick bushed trajectories by hitting the space bar. The user
extracts previously selected data from the current scatterplot and attaches them to
the mouse pointer so they appear in a “fly-over” view (transparent background).
