SPx Server

Host Systems

SPx Server is application software, designed to run on standard Intel PC or SBC hardware with Windows or Linux (see Spec tab), or on ARM hardware under Linux. The software is simple to install.

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. This allows small, low-observable targets such as drones to be detected and tracked alongside conventional targets in the same radar video. MBT extensions application note.

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 decrease, 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.

Three Versions Available

As standard, there are three main versions of SPx Server, each of which progressively adds additional processing functionality:

• SPx Distribution Server – includes primary radar digitisation and network streaming
• SPx Detection Server – adds both plot extraction and proximity detection processing
• SPx Tracking Server – offers a complete multi-hypothesis primary radar tracking solution

There are also embedded variants of each optimised for the HPx-700 Radar Input and Processing Unit.