Choose by the processing you need. The Distribution version digitises radar and streams video over the network; Detection adds plot extraction and proximity detection; Tracking adds complete multi-hypothesis primary radar tracking. Each version includes everything in the one before.
All three are the same SPx Server application with different licensed functions. Licences are protected by a USB dongle or a MAC-address licence file (other schemes are possible). Embedded variants of each version run on the HPx-700 radar input and processing unit.
Radar video can come from HPx-410 or HPx-450 cards, an HPx-346 or HPx-700 unit, or network radar video such as ASTERIX CAT-240. Radar recording is a separately licensed option. See licensing and support for more.
SPx Server outputs track reports in SPx format, ASTERIX CAT-48 or CAT-10, NMEA-0183 TTM, TAK and SAPIENT. Radar video is distributed in ASTERIX CAT-240 or SPx format.
- SPx: Cambridge Pixel’s own format, with the most comprehensive set of track data.
- ASTERIX CAT-48 or CAT-10: Eurocontrol standard formats; CAT-10 is for surface movement data.
- NMEA-0183 TTM: the maritime standard track message.
- TAK and SAPIENT: for interoperability with modern C2 systems.
See the radar standards FAQs for more on ASTERIX, and the SAPIENT FAQs.
Yes, provided you have licences for both. SPx Server has a single processing chain, so set that processing up for tracking rather than display; video processed for display, for example thresholded to reduce bandwidth, cannot share the chain the tracker uses.
Each of SPx Server’s 3 independent distribution channels can carry raw (unprocessed), processed or clutter-map video.
SPx Server finds spans of processed video above a threshold on each return, joins them across returns into connected two-dimensional shapes, and records each shape as a plot with its weighted centre of gravity, bounding box, total weight and timestamp. Size limits reject small noise, large clutter and land.
Before extraction, the radar video is cleaned up with CFAR thresholding, clutter map generation, area-based filtering and masking, and sidelobe suppression, so fewer false plots are produced.
No merging of close plots happens at the extraction stage. Partial plots can therefore be reported on the network if wanted, and the tracker decides whether to merge plots in the context of the local tracks. Optional plot merging (several modes) and configurable plot geometry (minimum and maximum range and azimuth) are available.
SPx Server's AI-assisted configuration uses machine learning to suggest plot extraction parameters from your live radar data. SPx Server can also receive plots from radars that produce them, and can act as the plot extractor for SPx Tracker-3D. See plot extraction for background.
SPx Server's track filter computes a dynamic filter gain from estimated system noise and measurement noise models, so the gains change continually: they rise when the target manoeuvres or uncertainty increases, and fall in steady-state tracking. A simpler fixed-gain mode is also available.
System noise models uncertainty in the target's known dynamics, including its ability to manoeuvre. As system noise increases, or measurement noise decreases, the filter places more weight on the new measurement and the gains increase; as system noise decreases or measurement noise increases, the gains fall. Under certain assumptions about the noise and linearity, this gives an optimal estimate of the true target position.
Fixed gains can work well where targets are clearly identified and relatively clutter-free. The multi-hypothesis tracker updates the estimated position separately for each hypothesis.
A hypothesis is one possible interpretation of how new plots associate with existing tracks. SPx Server’s multi-hypothesis tracker holds several hypotheses at once and reports the one with the highest confidence, so the correct interpretation can be chosen as soon as new data resolves it.
With limited data, it is sometimes impossible to pick the right interpretation immediately. Holding multiple hypotheses lets the correct one be deduced as new data arrives, which gives significant improvements in performance over simpler single-hypothesis trackers. Close tracks are processed together as a cluster so that all possible plot-track associations are considered.
You can switch SPx Server to single-hypothesis mode if you prefer. SPx Server also switches to single-hypothesis mode automatically, as part of load reduction, if it becomes overloaded.
Model Based Tracking (MBT) is an SPx Server extension that runs several sets of tightly coupled tracking parameters, called models, on the same radar video. MBT lets small, low-observable targets such as drones be detected and tracked alongside conventional targets, much like running multiple trackers with different parameters.
Each model lets the track processing look specifically for a certain type of target. For example, MBT can be used for small target detection, or models can be configured to look for air and surface targets in the same data set. MBT can handle a larger number of provisional tracks than the standard multi-hypothesis tracker’s initiation process.
MBT is available from SPx Server V1.72 onwards, and the “New MBT Extensions to SPx Server” application note on the SPx Server page explains it in more detail. With manual track initiation, a track can be created with a model whose parameters suit the target, for example a highly manoeuvrable target.
Yes, but only to a limited degree. SPx Server tracks in 2D and is designed for rotating radars; SPx Server can tag height information into its track reports. For true 3D tracking, or radars with non-rotating or variable updates such as electronically scanned radars, use SPx Tracker-3D.
SPx Tracker-3D takes plots from the radar or from an external plot extractor (SPx Server can do this), tracks with a Kalman filter, supports height-dependent area parameters and terrain visibility processing, and outputs ASTERIX CAT-48 or SPx track reports.
In most cases, SPx Tracker-3D is used for air targets, such as air surveillance and drone detection, while SPx Server is used for coastal surveillance, maritime and airport ground movement applications.
Yes. SPx Server extracts and tracks targets from secondary surveillance radar (SSR/IFF) transponder video as well as primary radar, decoding interleaved Mode 1, 2, 3/A and C codes in software. The codes are embedded in each plot and used to strengthen track association.
Interrogation mode tags can be embedded at the start of the IFF video as P1/P3 pulses, or a specific mode can be set, so SPx Server knows which replies to expect. Processing includes de-FRUITing and de-garbling to remove typical IFF noise. The video must be sampled at sufficient resolution.
This software approach is a cost-effective alternative to dedicated hardware IFF decoders. IFF processing is also an option on the HPx-700. To display primary and secondary radar video and tracks, use ASD-100; to fuse IFF, ADS-B and primary tracks, use SPx Fusion Server.
SPx Server has programmable minimum and maximum target speeds, for initiation and tracking, from 0 to 1000 m/s. High-speed targets can be tracked with appropriate configuration; the practical limit depends on how far the target moves within the radar data store, which depends on the radar’s maximum range.
At the maximum initiation speed of 1000 m/s, the minimum initiation range is 10 NM for targets moving tangentially to the radar and 3 NM for targets moving radially towards or away from it. It is therefore difficult to track high-speed targets with short-range radars.
Minimum and maximum initiation speeds can be set differently in different areas.
Yes, provided SPx Server is configured correctly. Dynamic (CFAR) thresholding automatically adjusts the detection threshold as clutter levels change, and other track-processing parameters adapt automatically to conditions. There are limits to how far this adaptation goes.
SPx Server’s clutter processing includes:
- Adaptive CFAR thresholding using a moving-window average.
- Clutter mapping using scan-to-scan correlation, and clutter subtraction to give pseudo-MTI video. Clutter-map video can also be sent out on a distribution channel.
- Area-based video filtering and masking, and sidelobe suppression.
On small vessels such as USVs, automated pitch and roll correction helps keep accuracy as the sea state changes. Where conditions differ by location, use area-dependent tracking parameters.
Yes. SPx Server masks radar video with user-defined polygons, fixed to the world or to the platform, including holes, on static or moving platforms, so a sector or any other area can be blanked. Land can be masked automatically using the built-in world shoreline database.
- Land masking: uses the built-in world vector shoreline database (static installations only). Plots over land can also be suppressed automatically, on static or moving platforms.
- No-ATI zones: suppress automatic track initiation in chosen areas.
- Area-dependent tracking parameters: change how tracking behaves in an area rather than blanking it.
Sector blanking can also be done before SPx Server: the HPx-346 includes sector blanking in its video processing, and some radar controllers give access to the radar’s own sector blanking control, depending on the radar model.
Yes, to a limited degree. SPx Server has built-in AIS association: SPx Server can associate a radar track with an AIS track and include the AIS ID in the track report. For more flexible fusion of radar, AIS, ADS-B and IFF tracks, use SPx Fusion Server.
SPx Server can also display and record AIS tracks. SPx Fusion Server combines track reports from up to 32 sensor inputs per licence, uses priority and scoring to choose the most reliable data, and keeps consistent track labels across the combined coverage.
Yes. SPx Server has been verified by simulation against the standardised test scenarios in IEC 62388 section 10.3.14 (target motion and tracking accuracy).
SPx Server also works with open standard data formats: ASTERIX, the Eurocontrol standard, for radar video and tracks; NMEA-0183 for track output and navigation input; and SAPIENT.
SPx Server has a user interface to help you configure, tune and analyse the processing, with live views of radar video, plots and tracks that show the effect of each change. Once deployed, SPx Server can run headless, without the user interface, controlled through its network API.
The main interface is browser-based and served locally by SPx Server, with no internet connection needed. A native Windows GUI is also available but is not essential; the native GUI needs a display resolution of at least 1024×768.
Use the SPx Server web interface: connect a standard web browser to SPx Server to monitor and control it remotely. Alternatively, view the native user interface on a remote computer with remote desktop. For health monitoring across several systems, use SPx Monitor.
The web interface is served locally by SPx Server, with no internet connection required, and provides control and graphical monitoring; SPx Server is configured, tuned and verified through it, and the native interface is not essential. SPx Server also has a network API for remote control.
SPx Monitor detects faults such as applications not running, system overloads and missing input sources, can restart stopped applications automatically, and shows which tracker is active in a redundant pair.
In automatic track initiation (ATI), SPx Server creates tracks itself by looking for target-like returns in the radar video. In manual acquisition, something outside SPx Server, such as an operator clicking a target on a display, tells SPx Server where to create a track; SPx Server then maintains it.
Manual initiation requests can come from an operator or from another system. ATI can be turned off if only manual initiation is needed, or suppressed in chosen areas using no-ATI zones.
Manual initiation can also create tracks with extra information, if known. For example, for a highly manoeuvrable target, SPx Server can create the track with a model whose parameters suit that target (see Model Based Tracking).
SPx Server’s track acquisition time is programmable. In low clutter, a new track can be established after as few as 2 detections (2 scans); where the plot extractor reports false detections, the provisional stage can be extended. Shorter times detect targets faster; longer times reduce false tracks.
- Initiation time is set from 2 scans upwards using an M:N or SPRT integrator.
- Initiation criteria, and minimum and maximum initiation speeds, can be different in different areas.
- Because acquisition is counted in scans, the time in seconds depends on the radar’s scan period.
- Model Based Tracking can handle a larger number of provisional tracks than the standard initiation process.
Yes. SPx Server can record radar video, together with NMEA and AIS data, for trials and offline analysis. Recording is a licensed option; without the licence only short recordings are permitted. To enable recording, set the ProRecord.Available parameter to 1.
Use the ProRecord parameters to set a file prefix if required. If the prefix includes a directory name, that directory is not created automatically, so create it first.
Recordings can be replayed in SPx Server, read with SPx Open Access for analysis in C++, .NET or MATLAB, or sent to Cambridge Pixel engineers for configuration advice. For continuous recording with managed storage, use RDR Data Recorder.
No. SPx Server’s recording is designed for capturing recordings during trials, for offline analysis and configuration, not for continuous recording. SPx Server cannot manage a recording session to keep, for example, the last N days. For continuous recording with managed storage, use RDR Data Recorder.
Recording in SPx Server is a licensed option; without the licence, only a short recording time is permitted. RDR Data Recorder records radar and camera video, audio, targets and network data on multiple channels.
Yes. You can upgrade SPx Server to the latest version for one year after initial delivery. After that, you need a support contract in place; contact our sales team for details.
SPx Server is under active development; recent releases added AI-assisted configuration, TAK and SAPIENT output, proximity detection, HPx-700 support and a radar coverage display. To check the latest version, see Software Versions. Register your product to be told when updates are available, and see support and maintenance for support contract options.
Ask Cambridge Pixel engineers: they often supply a customised configuration file as a starting point, with suggested parameters to adjust. The best SPx Server settings depend on the radar, the targets and your priorities, such as fast acquisition or fewer false alarms, so no single procedure fits every system.
- Record some radar video with SPx Server’s recording function and send it to our engineers for initial advice.
- Load the customised configuration file they provide, then adjust the suggested parameters.
- Use SPx Server's AI-assisted configuration, which uses machine learning to suggest plot extraction parameters from your live radar data.
- Use the browser interface’s live display of video, plots and tracks to see the effect of each change.
- Use area-dependent parameters to solve local problems without affecting tracking elsewhere.
The SPx Server manual set explains each control, and the “Tracking from Video in SPx Server” application note on the SPx Server page is also useful. Contact support for help.
Create named area objects, such as polygons or segments, then give tracking parameters different values inside those areas. SPx Server uses the area value where one applies and the global value everywhere else, so you can solve a local problem without changing tracking elsewhere.
By default, tracking parameters apply everywhere. For any track processing, SPx Server first checks for area-dependent values; if there are none, the global value is used. Most tracking parameters can be area-dependent, including track initiation criteria and minimum and maximum initiation speeds. No-ATI zones, which suppress automatic track initiation, are a related area-based control.
Area dependency applies only to tracking parameters, not to plot extraction or video processing parameters. To remove video in an area, use polygon masking instead.
A provisional track is a new track that SPx Server has not yet confirmed. SPx Server creates a provisional track when a plot does not associate with any existing track, and promotes the track to established once confidence has built up over a number of detections.
Many more provisional tracks are created than become established, because most are associated with noise or clutter and are deleted. How long a track stays provisional is configurable: as few as 2 detections in low clutter, longer where the plot extractor reports false detections. The setting balances speed of detection against the likelihood of a false alarm.
Provisional tracks can be shown in the user interface, which is useful for analysis. A track ID is allocated when the provisional track is created, which is why some IDs never appear in track reports.
A cluster is a group of one or more tracks that are close enough together for SPx Server to process them as a group. Processing close tracks together ensures that all possible associations of plots and tracks are considered. A sufficiently isolated track forms a cluster on its own.
Use SPx Server’s built-in lossless compression, zlib or ORC (Open Radar Coding), and if needed simplify the video before compression, for example by thresholding it to a single bit and removing low-level background noise. Simplifying the video improves compression but loses some video content.
SPx Server distributes radar video over standard networks using UDP, unicast or multicast, so any number of clients can receive it. The compression achieved depends on the radar video and may change over time; zlib generally compresses more than ORC, at the cost of slightly more CPU time. Typical data rates range from 2 Mbit/s for processed video to 10 Mbit/s, depending on the input and configured resolution.
The processing stages are also used by the target tracker, which normally takes priority for the processing settings. For low-bandwidth or unreliable links, use RadarLink.
Your SPx Server licence probably does not include tracking. SPx Server enables its radar processing functions according to the licence: the Distribution version, for example, distributes radar video but does not enable plot extraction or target tracking. Tracking needs the Tracking version.
The three versions of SPx Server are Distribution (radar digitisation and network streaming), Detection (adds plot extraction and proximity detection) and Tracking (adds multi-hypothesis tracking). Contact us about upgrading your licence.
Reduce the number of plots first, then check tracking parameters. SPx Server falls behind when processing, plot extraction or tracking is configured incorrectly. SPx Server tries to self-correct by switching to simplified processing, such as single-hypothesis tracking, but this may not be enough or may not be what you want.
- Disable tracking and look at the radar processing and plot extraction. Make sure plots are extracted only for possible targets, not for excessive clutter or noise.
- Change the video or plot processing to restrict the number of plots generated.
- Re-enable tracking and check the tracking parameters are reasonable: track dynamics, acquisition time and acquisition area.
- In areas of high plot density, disable track processing or use area-dependent parameters to increase the acquisition time.
- Check the host meets the recommended specification: Intel Core i5 (10th generation or newer) with 16 GB RAM, or ARM Cortex-A72 or better.
SPx Monitor can alert you to system overloads.
Radar position measurements always contain some error, and a track’s estimated speed and heading partly reflect that error. In SPx Server, lower steady-state filter gains apply more filtering, so speed and heading settle as the noise is filtered out; gains rise automatically during a manoeuvre and fall again afterwards.
The tracking filter assumes the target is moving at constant speed and heading. If the filter sees a significant error in the track’s position, the filter increases its gains to follow the target through the manoeuvre, then reduces them again to improve the speed and heading estimates. The manual gives guidelines on steady-state filter gains for different tracking situations.
On a ship where SPx Server applies North offset compensation, timely updates of the ship’s heading are critical for good tracking performance. As a guide, the sample specification gives speed accuracy of σ = 5% of true speed above 5 m/s (10% below 5 m/s) and course accuracy of σ = 1 degree, for a 100 m² RCS target in sea state 1; actual figures depend on the radar, target and configuration.
SPx Server allocates track IDs from 1 to 4095 on a least-recently-used basis. When a track is deleted, its ID is not reused until all the other IDs have been used.
An ID is allocated when a track is created as a provisional track and kept when the track becomes established. SPx Server can track up to 4000 targets.
The missing IDs were used by provisional tracks that never became established. SPx Server allocates a track ID when it creates a provisional track; if the provisional track is deleted before it is established, that ID never appears in a track report.
For example, if you see track IDs 1, 2 and 4 for three tracks, ID 3 was used by a provisional track that was deleted. IDs are reused only after all others in the 1 to 4095 range have been used.
Usually because the radar video has a small range bias. SPx Server can correct this with one of our standard plugins, which applies a fixed range offset and a range multiplier. Contact support for details.
If the error is in bearing rather than range, check the azimuth reference. Incoming azimuths can be ship- or North-referenced, and SPx Server converts them to North-referenced using navigation data (NMEA-0183, such as HDT or HDG), so timely heading updates are essential. On small vessels, automated pitch and roll correction also helps accuracy.
SPx Server’s built-in screen recorder captures images of the PPI window at regular intervals and saves them to a directory. Use the screen recorder when analysing problem cases, to capture images showing detailed on-screen information.
No questions on this page match .
Last updated
Meet us at: