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Frequently Asked Questions

This page features the frequently asked questions that we receive from our customers related to Cambridge Pixel products and services. If you need help and support, please get in touch with us at: [email protected]

SPx Server

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Why is there a user-interface for a server product? 

The user-interface is provided to assist with configuration and analysis. When operating as a server the user-interface is not required and SPx Server can be configured to start without one if desired.

Why does my SPx Server not support target tracking? 

SPx Server supports several different radar processing functions according to a license. If you have purchased SPx Server for radar distribution, for example, it will not enable plot extraction and target tracking.

What is the MBT? 

The MBT (Model Based Tracking) module is a component of SPx Server for target tracking. It provides options for creating a set of tightly coupled tracking parameters (the model) that allow the track processing to look specifically for certain types of target. The MBT can be used for small target detection, for example, or models can be configured to look for air and surface targets in the same data set. It is very similar to having multiple trackers processing the same data with different parameters,

Does SPx Server automatically adapt to changing sea-state or weather conditions? 

Yes it should, provided it is configured correctly. The dynamic thresholding process will automatically adjust the detection threshold to accommodate changing clutter levels (CFAR). Other parameters in the track processing provide automatic adaption to conditions. There are limits though to this adaption.

How can I monitor SPx Server across a network interface? 

There are two options to this. One is to use a remote desktop to permit the SPx Server user-interface to be seen on a remote computer. However, the preferred way is to use the browser interface option. This allows a standard web browser to connect to SPx Server. There are some limitations of control through the web browser versus the native interface.

Can SPx Server be used to distribute radar video and track targets at the same time? 

Yes, subject to having the licences. It is important to note that there is only a single processing chain and that processing should be optimised for the track processing function, rather than the display. If it is desired to process the radar video for display (for example to threshold it for reduced bandwidth or simplified display) then that cannot use the same processing chain as the tracking.

What type of tracking filter is used by SPx Server? 

SPx Server uses an adaptive alpha-beta tracker. The gains for the tracking filter are automatically adjusted so that lower gains are used for steady-state tracking and higher gains are used when there is increased uncertainty or manoeuvring. This is similar in principle to the behaviour of the Kalman filter.

How do I configure SPx Server to get the best tracking results? 

This is a difficult question, because it depends on the radar, what types of targets are being processed and what is most important in the processing (for example acquisition speed or reduced false alarms). The SPx Server manual set provides a reference and explains the controls but it does not, and realistically cannot, provide a step-by-step procedure. Cambridge Pixel engineers are available to provide assistance for tracker configuration and often this means that our engineers will provide a customised configuration file as a starting point, with suggested parameters to adjust to. SPx Server provides a radar recording capability which can be used to capture radar video that can be sent to our engineers for initial advice.

Can SPx Server be used to combine radar tracks with AIS? 

Yes, to a limited degree. There is a built-in capability in SPx Server to associate a radar track with an AIS track and the associated AIS ID appears in the track report. There is more flexibility and options using a separate SPx Fusion Server, but simple association of tracks and AIS if possible within SPx Server.

How can I use area-dependent parameters? 

This is an important capability of SPx Server. By default, tracking parameters affect the behaviour of tracking everywhere. However, sometimes it is desirable to use different parameters in restricted areas, perhaps to solve a local problem. To do this, create new area objects, for example as polygons or segments. These named area objects can then be used to give tracking parameters different values in those areas. For any track processing, the value of a tracking parameter to use is found by first checking any area-dependencies. If there are non, the global value is used. Most tracking parameters can be area dependent. Note that area dependency only relates to tracking parameters, not plot extraction or processing parameters.

What are hypotheses? 

The tracker is a multi-hypothesis tracker. This means that it is able to consider different possible interpretations of how new plots associate with tracks.. Each interpretation is called a hypothesis. The best hypothesis is the one with the highest confidence and that is the one that gets reported. Sometimes it is not possible to get the right interpretation based on limited data, so holding multiple hypotheses allows the correct interpretation to be deduced as soon as new data is received. It is possible to switch the tracking into single hypothesis mode if desired. Note also that the tracker will automatically switch into single hypothesis mode as part of load reduction if it gets overloaded.

What are clusters? 

A cluster is a collection of one or more tracks that are close enough together that the processing considers them as a group. A cluster may comprise one track if that track is sufficiently isolated from any others. It is necessary to process close tracks as a group to ensure that all possible associations of plots and tracks are considered.

What are provisional tracks? 

When a track is first created, which occurs when a plot is unassociated with any existing track, it is provisional. It remains in the provisional state for a number of detections, until confidence has built up and it can become an established track. There are typically many more provisional deleted because they are associated with noise or clutter. Provisional tracks can be displayed in the user interface, which is useful for analysis. The amount of time a track remains provisional before being promoted to established is configurable.

How can I reduce the bandwidth of distributed radar video with SPx Server? 

SPx Server can be used to distribute radar video over a standard network using UDP/IP protocols, allowing any number of clients to receive the video. Radar video can be compressed with one of two built-in compression schemes, which are lossless, but the degree of compression achieved is dependent on the radar video and may change over time. There are several processing options that may be configured to simplify the video and make it more compressible, albeit with some loss of video content. For example, the video can be thresholded to a single bit, optionally taking out low-level background noise. Note that SPx Tracking processing stages are also used by the target tracker, which normally takes priority for the settings of processing.

SPx Server appears overloaded and not keeping up. What should I do? 

When configured for track processing it is possible that SPx Server cannot keep up with incoming radar. This is the case if the processing, plot extraction or tracking are incorrectly configured. SPx Server will attempt to take some steps to self-correct by automatically switching to simplified processing, but this may not be enough or it may not be the desired behaviour. The situation must be considered by first disabling tracking and looking at the radar processing and plot extraction to ensure that plots are being extracted only for possible targets and not for excessive clutter or noise. Changes to the video or plot processing should be first used to restrict the number of plots being generated. Then for the track processing, ensure that tracking parameters are not unreasonable, i.e. track dynamics, acquisition time, acquisition area etc are all reasonable. For areas of high plot density, for example, track processing may be disabled or area-dependent parameters may be used to increase the acquisition time.

Can I update SPx Server to the latest version? 

SPx Server is under active development and we are continually making improvements. You may upgrade to the latest version of the software for one year after initial delivery. After that time you need to have in place a support contract. Contact our sales team for details.

We recommend you register your product to receive notifications when updates are available.

Can I record radar video in SPx Server? 

Ensure that the ProRecord.Available parameter is set to 1. Use the ProRecord to set a file prefix if required (note that if a directory name is specified, the directory will not be automatically created).

Can the recording capability of SPx Server be used to provide continuous recording? 

The recording capability of SPx Server is not intended to support continuous recording. There is no capability to manage the recording session to maintain the last N days, for example. The recording capability of SPx Server is to support the capture of recordings during trials. This permits offline analysis and configuration of the software. The recording capability is a licenced option. Without the license only a short recording time permitted. For continuous recording with managed storage, please consider our RDR Data Recorder software.

The track IDs from SPx Server appear to have some numbers missing. Why is this? 

A track ID is allocated when a track is created as a provisional track. The same track ID is used when the track becomes established. If the provisional track is deleted before becoming established the track ID may never be used in a track report. For example, you may see track ID 1, 2 and 4 appearing for 3 tracks. This will mean that ID 3 was used for a provisional track, which never became established.

How are track IDs allocated? 

Track IDs are allocated on a least recently used basis with valid IDs are from 1 to 4095. If Track ID 1 is used and then that track is deleted no new track with same ID will be used until all other track IDs have been used.

What format of track reports are available? 

SPx Server can output SPx, ASTERIX and TTM track reports. SPx format is Cambridge Pixel’s own format and this provides the most comprehensive set of data for a track. The ASTERIX format (CAT-48 or CAT-10) is the Eurocontrol standard format. TTM format is the NMEA Maritime standard.

Does SPx Server support any specific international standards? 

SPx Server has been verified by simulation against the standardised test scenarios in IEC 62388 section 10.3.14 (target motion and tracking accuracy).

Does SPx Server support 3D radars? 

SPx Server has very limited support for 3D radars. It is able to tag height information into the track report, but the tracking is 2D. For true 3D tracking, or for radars with variable update rates, please consider our SPx Tracker 3D product.

What is the maximum speed of target that can be tracked with SPx Server? 

There isn’t a maximum speed built into the software. It is possible to track high-speed targets with appropriate configuration. An important consideration is how far the target moves in the data store and this depends on the radar’s maximum range. It is difficult to track high-speed targets with short range radars, for example.

Why is the estimated speed/heading of a track varying more than expected? 

Since measurements of a track’s position by the radar are always subject to error, the estimated speed and heading will, to some extent, reflect that measurement error. The gains of the tracking filter are key to improving the estimated values for speed and course, on the assumption that the target is moving at a constant heading and speed. Reducing the steady state filter gains will apply more filtering and the estimated speed and heading will, eventually, stabilise as the noise is filtered out. If the tracking filter starts to observe a significant error in the position of the track it will start to increase the filter gains to track the target through a manoeuvre. Once the target has completed the manoeuvre the filter gains will automatically reduce again to improve the estimated speed and heading. Refer to the manual for guidelines on the steady-state filter gains for different tracking situations.

What’s the difference between manual and automatic track acquisition? 

In manual track acquisition, it is the responsibility of something outside of SPx Server to define a position where a new track should be created. For example, this could come from a user-interface, where the user observes video from a target and then clicks that location, resulting in a message being sent to SPx Server to initiate a track. SPx Server will continue to maintain the track with subsequent updates of the radar video. In automatic track initiation (ATI), SPx Server creates new tracks automatically by examining the radar video to look for target-like returns. ATI can be turned off if manual (external) initiation alone is required. Manual initiation offers the option of creating tracks with additional information, if known. For example, if it is known that the target to be tracked is a highly manoeuvrable target, SPx Server can create a track and associate a model with appropriate parameters.

What’s the purpose of SPx Server’s Screen Recording capability? 

The built-in screen recorder is able to capture images from the PPI window at regular intervals and save in a directory. This can be useful during analysis of problem cases when it is desired to capture images showing detailed information on the screen.

Why are my radar echoes not aligned with real world objects e.g. coastline or AIS targets? 

Some radars may show a small bias in the range of radar video. This can be corrected where necessary using one of our standard plugins to support a fixed range offset and a range multiplier. Contact us for further details.

Please can you confirm whether there are any export controlled parts (e.g. ITAR) for the SPx Server or the SPx Fusion server? 

Those products are manufactured in the UK and are not subject to export control, including ITAR.