A system of locally connected sensors has the task of tracking moving targets which pass by. In each of these movies, 100 sensors are deployed in the field by placing them close to an underlying grid. We consider square, honeycomb and triangular lattices, each with a nearest neighbor distance of 10 units. Each sensor is displaced from this lattice randomly by up to +- 1 unit in both the N-S and E-W axes. The probability that two sensors have a communications link depends on distance. It is close to unity for nearest neighbors, roughly 50% for second neighbors, and falls off exponentially beyond 19 units.
Targets appear at the left and fly a twisting path through the sensor array.
If a target leaves the picture, a new target appears on the left to keep the number
of targets constant. A green circle around each target shows the range at which they can be detected.
Various range values R (R=15, 20, 30, 40) are considered.
Our job is to ensure that each target is tracked
by at least three communicating sensors for long enough to do something about it.
Such groups of three or more communicating sensors tracking the same target
we call a "tracking cluster" or TC.
No sensor can track more than one target.
Each sensor has three fixed 120 degree antenna sectors.
At the start of the simulation, each sensor is given a random orientation,
and subsequently they do not turn.
The active sectors are shown in each frame of the movie, with a red line
connecting them to the target being tracked.
We only show active sectors and red lines for the sensors
which succeed in being part of a TC.
The thermometer at the right of each frame shows the fraction (from 0 to 100%)
of targets which are tracked by one or more TCs.
The final frame in each movie shows coverage for each target as a time line.
The specific color at a certain point in time represents the number of TCs
tracking simultaneously the proposed target.
(For the color coding have a look at the
table.)
How the quality of the results depends on the amount of calculation time spent is shown on the next page.