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18.4.4 Two-dimensional Mono Tracking

The primary function of the two-dimensional tracking module is fairly straightforward: Given two-dimensional data sets arriving at reasonably regular time intervals (scans) from the sensors, construct a big set of ``all'' plausible two-dimensional tracks linking these observations from scan-to-scan. This is done by way of a simple track-splitting module. The tracks from the two two-dimensional trackers in Figure 18.17 are the fundamental inputs to the three-dimensional track initialization algorithm described in the next subsection.

The adoption of track splitting in place of optimal association for the two-dimensional trackers is largely a consequence of assumption (A1) above. Without a restrictive model for the (unseen) motion along the sensor line of sight, the information available to the two-dimensional tracker is not sufficient to differentiate among plausible global track sets through the data points. Instead, the two-dimensional tracker attempts to form all plausible ``tracks'' through its own two-dimensional data set, with the distinction between real and phantom tracks deferred to the three-dimensional track initiation and association modules described in the next section.

With the receipt of a new data set from the sensors, the action of the two-dimensional tracker consists of several simple steps:

  1. Extend existing tracks to new data, as possible.
  2. Redistribute the global track file among the nodes (concurrent execution).
  3. Collect and sort ``good'' two-dimensional tracks into a global two-dimensional report list.
  4. Initialize new entries for the track file.
This algorithm flow is illustrated in Figure 18.18. Discussions of the track file redistribution in Step 2 (as well as concurrent aspects of the other steps) are deferred. The following subsections describe track extensions, report collection, and track initiation.

Figure 18.18: Processing Flow for two-dimensional Mono Tracking

Guy Robinson
Wed Mar 1 10:19:35 EST 1995