Database Reference
In-Depth Information
Figure 12.4 Union Boolean operation.
12.4.6 Example of Usage
In this scenario, we use one day of recordings of aircraft trajectories over
France. In this data set, a unique and incremental identifier is assigned to each
trajectory. The first trajectory of the day has the number 0
, the next one has the
number 1
, and so on. Figure
12.5
shows an abstract visualization of this data
set. The
x
screen axis shows the time of each radar plot and the
y
screen axis
shows the aircraft's identifier. Since these identifiers are incremental over the
day, the resulting visualization shows a noticeable continuous shape, in which
each horizontal line represents the duration of one flight. The slope of the shape
indicates the traffic increase during the day (due to the incrementally assigned
identifiers). Hence, the traffic notably increases at 5 A.M. and decreases at 10 P.M.,
as reflected in the change of slope. The width of this shape indicates the average
flight duration in the data set: it is about 2.5 hours, which represents the average
time taken to cross France. But some aircraft have longer trajectory durations.
The user brushes these long trails (the ones that come out of the curved shape).
When visualizing them with a latitude (
y
screen) and longitude (
x
screen) visual
configuration, the user discovers a figure eight-shaped trajectory. This trajectory
covers 6 hours and performs 11 loops. After further investigation, it is found
that it corresponds to a military supply plane.
Figure 12.5 Detection of supply planes with an abstract visualization.
