SPx Plot and Track Fusion

SPx-FUSE, a component of the SPx radar processing family, is a COTS software module that combines plot and track information from multiple trackers into a single correlated track. For a complex radar installation with multiple overlapping radars, SPx-FUSE provides a single integrated track database by combining tracks from the multiple sources. The module can be set-up from configuration files to allow turn-key operation and can be monitored and controlled by a user interface running either locally or remotely to the system.

SPx-FUSE can be configured to receive radar plot and track reports from up to 8 sources. Positional information for each remote source is configured in SPx-FUSE and retained in configuration files which are loaded on start-up of the module. During operation, SPx-FUSE receives track reports from each sensor. There is considerable flexibility in the data that can be processed by SPx-FUSE, with the standard set of track descriptions including filtered and measured position, speed and size. SPx-FUSE associates observations from one sensor with any overlapping sensors and identifies measurements that are believed to derive from the same target.

The combination rules for processing multiple reports allow for flexibility in the configuration of the system. In one mode, the total coverage area can be mosaiced, so that a report from a preferred radar is used at each location of the target. In this mode, SPx-FUSE selects the correct track report as a function of the target?s position, switching sources as the target moves across the boundary of the mosaic. In another mode, SPx-FUSE selects the best track on the basis of a quality measure, which is can either be calculated by the module automatically, or else derived from information in the incoming track report.

An internal track database retains the current track information which is periodically sent to remote clients over an Ethernet network. Standard TCP/UDP protocols are used to facilitate distribution to multiple clients in a multicast mode. The same network may be used to control and monitor SPx-FUSE with a graphical user interface that provides an animation of the internal state. This can be used to verify the receipt of data from the remote trackers and ensure valid data is being delivered from SPx-FUSE.

Combination Rules

When SPx-FUSE has associated tracks it can establish a link between the reports coming from the remote trackers. For example, if track id X from tracker A is associated with track id Y from tracker B, then all future track reports of X and Y can be related to each other. SPx-FUSE has made an association and uses the track ids allocated by the remote tracks as the key to join the reports.

With the association made, each new report for X or Y causes SPx-FUSE to make a decision about how to process the report and what to report itself. The Rules for Combination control how SPx-FUSE handles the reports.

SPx-FUSE provides options for the method to combine track reports. Theses options include:

• Preferred sensor. In the situation where two sensors overlap, it might be preferable to use the observation from a preferred sensor that is known to be more reliable. In this situation, the preferred sensor is defined to SPx-FUSE and the other sensors in that area are ignored. Of course as the target moves out of the coverage of the preferred sensor, the non preferred sensors have to take over.
  
• Best Sensor. In the Best Sensor mode, SPx-FUSE makes a judgement about which sensor is providing the best information in the overlap region. The other sensors are ignored, until such time as they are regarded as providing the best information. The decision on best observation is based on historic measurements from the sensors. For example, a sequence of measurements that have a low variability suggest a combination of an accurate measurements process and well-known target dynamics, so that sensor is preferred.
  
• Weighted Sensor. In this mode, the information from multiple sensors is combined with a weighting that is dependent on the historic accuracy of the sensor information. For example, if one sensor has provided very regular measurements, and the other more erratic or missing measurements, then more emphasis is given to the accurate sensor. This is just a more general case of the Best Sensor mode.
  
• Fixed Weighted Sensor. This is just a special case of the weighted sensor mode above, in which the weighting given to each sensor is fixed.
  
• Shift Weight. In this mode, which is another variant of the weighted sensor method, the weight given to two measurements is shifted as the target moves across the intersection. Just as it enters the intersection, the weight is 100% sensor 1. As it leaves the intersection the weight is 100% sensor 2. As it moves between the weight is proportional to the distance, so that at the midpoint the weight is 50% sensor 1, 50% sensor 2.
  
• Range Preferred. In this mode, SPx-FUSE uses the principle that the range measurement of a track is often more accurate than the azimuth estimate. So an improved estimate of position can be made by using range measurements only.
  
• User-defined. There is the option to add your own code to define the combination mode. This code could implement any combination strategy, possibly including some of the built-in modes listed above.
  

SPx-FUSE defines a set of criteria for measuring the quality of a track report and fusion product. On the assumption that the targets are moving in straight-lines with occasional changes of heading, SPx-FUSE calculates the variance in the reported positions as an indication of the quality of the tracking.

The ability for SPx-FUSE to internally monitor the success of its own fusion means it can run a number of fusion strategies in parallel and make a decision on the most effective.

Download an SPx-FUSE Technical Note (pdf format) here.