SPx Server (Tracking & Distribution)

Host Systems

SPx Server is application software, designed to run on standard Intel PC or SBC hardware.

The software is simple to install and the following minimum specificiation is suggested:

• Intel Core i5 or better CPU
• 8GB or more of RAM
• Windows 10 or 11 / Linux (mainstream distribution such as Red Hat, CentOS, Fedora and Ubuntu) less than 2 years old

Target Extraction

The SPx Extraction process examines the processed video to search for target-like returns that form a connected target-like shape. A set of configurable parameters define the target size of interest, allowing small noise returns or larger clutter or land masses to be eliminated early in the processing.

The extraction process begins by creating a set of spans that represent intervals of video above a threshold for each processed return. These spans are then combined across returns to form connected two-dimensional shapes. The weighted centre of gravity, bounding box and total weight of the plot shape are calculated and entered into a plot database, along with a timestamp. At this stage of the processing, no merging occurs of close plots that are likely to be derived from the same target. This allows partial plots to be reported on the network, if desired, and allows the tracking process to consider the merits of merging in the context of the local tracks.

Secondary Surveillance Radar Extraction

Interrogation mode tags may be embedded at the start of the IFF video stream as P1/P3 pulses or a specific mode specified, telling SPx Server which responses to expect. The processing includes de-FRUITING and de-garbling to remove typical noise from an IFF video.

The IFF video handling capabilities provide a viable, highly cost-effective alternative to traditional hardware-based IFF decoding systems.

Track Creation

The tracker maintains an active track database, updated with new plot data from the data extraction stage. New tracks are added automatically or from a manual request (operator input or external process).

The automatic track creation occurs when plots entered into the database are uncorrelated, or ungated, with any existing known target. A new preliminary track is created and is updated with future detections until confidence is established that the track is likely to be a target of interest.

The time a track is held in the preliminary stage is a programmable option and needs to be set to balance the speed of detection with the likelihood of a false alarm. In a low clutter environment, where extracted plots are likely derived from real targets, the acquisition time may be as short as 2 detections. For noisy situations, where the plot extractor is reporting false detections, the integration time in the preliminary stage may be extended.

Model Based Tracking (MBT)

The MBT extensions to SPx Server (V1.72 onwards) can handle a larger number of provisional tracks than the standard MHT's initiation process. This allows specific target models to be created, meaning that different parameter configurations can process the same radar video. The ability to detect small targets and support multiple tracking modules may offer new opportunities for tracking. Click here for further details on the MBT extensions.

Track Filter

For each hypothesis, the tracker updates the current estimated position with the new measurement. If the measurement were known to be completely accurate, the update process would believe the measurement and the new estimate would be exactly the measured value. For various reasons, the measurement is inaccurate so the update process must take a weighted combination of the expected position and the measured position. This is the track filtering. SPx offers a number of track filtering modes. The simplest mode uses fixed gains in the components of the measurement. This can be successful for tracking applications where the target is clearly identified and relatively clutter free.

The filter works by computing a dynamic filter gain, K, based on estimated system noise and measurement noise models. The system noise is used to model uncertainty in the known dynamics of the target, including its ability to manoeuvre. As system noise increases, or equivalently as measurement noise decreases, the filter places more weight on the measurement so the filter gains increase. As system noise decreases or as measurement noise increases, the filter gains decreases causing less emphasis to be placed on the new measurement. The filter gains are continually changing and provide, under certain assumptions of the noise characteristics and linearity, an optimal estimation of the true target position.

Tracking Parameters

The tracking behaviour parameters may be set initially from a configuration file and may be adjusted during operation of the tracker using either a customer GUI or network interface. Parameters include:

• Min/max speed of target to be tracked
• Multi or single hypothesis association modes
• Fixed gain or adaptive gain
• Expected target dynamics
• Size limitations on targets to be tracked
• Measurement noise estimates

Redundant Operation

Dual instances can be run simultaneously to provide redundant operation for high reliability systems, with the secondary instance automatically taking over if the first instance fails, providing an uninterrupted stream of radar and target track data.

Additionally, SPx Fusion Server can support redundant operation, providing a consistent set of track IDs to clients in the event of failover, and SPx Monitor provides monitoring and diagnostics, showing which instance is active and automatically restarting applications that have stopped.