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Introduction

This page details the settings available for the tracker within the Channels tab.

There will be as many channels as you have carriageways. Each carriageway's channel can be individually configured.

Contents

Channel

Plot Extraction

Plots are grouped cells of the radar's detection range that have been recorded as containing an object.

Min Amplitude (pwr): Determines the minimum amplitude of a plot to be considered for extraction.

Min Plot Range (m): Determines the minimum size in range of a plot to be considered for extraction.

Min Range Span (bins): Determines the minimum number of consecutive range samples that must be in a plot before it is considered for extraction.

Min Blob Weight (cells): Determines the minimum number of cells (where a cell is a single power reading in either range or azimuth) that must be in a plot before it is considered for extraction.

Plot Merging

Once plots are extracted (using the ‘minimum’ settings mentioned above), this option determines whether plots that are in close proximity to each other should be merged into single, larger plots using the method selected in the Mode setting. E.g. a large articulated truck might return several plots (cab, trailer, etc.) but the operator needs to see this as a single object. There is no way for the radar to know if two separate plots are part of the same target or if each plot is a different target, however, plot merging works on the basis that if two plots are “close” enough then we consider them to be part of the same target, so we merge them together into a single plot / target. To achieve this, plots need to be intelligently merged together without combining smaller individual vehicles. The different modes decide how you want to merge and also how “close” they need to be before we merge.

There are three modes:

Azimuth Merging

This mode looks at the gap between plots in azimuth and also the distance they are apart.

This mode is good for targets which are moving perpendicular to the radar and are further away from the radar. Note that this uses Merge Azimuth and Merge Range. But like all azimuth measurements, these become less accurate with range because of the beam width spread.

Distance Merging

This mode looks at the distance between the centre of the plots and ignores the shape of each plot. This is quite a good approach for targets which have fragmented in multiple plots. In some situations, especially close to the radar, this approach is better than Shape Distance.

This only uses the Merge Range setting.

Shape Distance Merging

This mode looks at the distance between the edge of each plot based on the shape of each plot. So it will only merge plots which are within the specified distance from the edge of each plot. This mode is good for targets where the shape of the plot is clear.

This only uses the Merge Range setting.

Merge Range (m): How far to look for the next plot to merge in range. Consider this a 'merge window' - the value represents the length of the window along the range that looks for plots to merge.

Merge Azimuth (°): How far to look for the next plot to merge in azimuth. Consider this a 'merge window' - the value represents the width of the window along the azimuths that looks for plots to merge.

We recommend that Distance Merging and Shape Distance Merging are the most effective for traffic.

Users should be careful about correct usage of plot merging. Two extreme cases are possible:

  • A large vehicle may generate many large plots (as the radar beam sweeps the vehicle, it could hit it in several places). With plot merging turned off (or misconfigured) these plots would appear to be unconnected to each other, and would be more likely to be classified as several targets.

  • At the other end of the spectrum, several targets which are close to each other could be merged into a single track if plot merging is turned on and set too aggressively. For example a group of people could be merged together and this would have the potential to be classified as a vehicle.

Tracking

Initial Delay (s): A timeout period after start up, during which will not generate any tracks to allow a grace period whilst the tracker establishes the background clutter, etc.

Clutter Track Age Limit (days): The maximum period of time that Clutter Map data can be retained and used.

Filter Mode: This setting controls the tolerances used by the tracker for predicting movement.

Fixed Gain: This is the default setting. Fixed Gain is the most reliable setting for predicting movement, but it is less tolerant of tracks that are manoeuvring in an unexpected manner.

Dynamic: The Dynamic setting will use a combination of tolerances depending on what the track is doing. It will try and use Fixed Gain for targets moving in a predictable fashion, yet, when required, will be more tolerant of targets making unexpected movements; for example, tracking a fast-moving vehicle all the way around a bend.

Tracking Areas

Area: Select one of the Areas from the list located in the Configuration Tree.

Parameters: Select the Tracking Parameter from the Configuration Tree.

Proximity Suppression

Track Margin (m): The radius of the Proximity Suppression Area.

Wake Suppression

This is typically used to suppress the generation of unwanted targets caused by the wake behind a boat. This feature calculates a suppression zone based on an angle and distance behind the boat. There are two options for calculating the distance, it can either be a fixed distance or can be based on time. Note that the time option includes an expansion factor which adjusts the suppression zone based on the size of the boat.

Wake Angle (°): θ , Theta. The angle of the wake spreading from the boat.

Wake Distance (m): x, the length of the wake.

Wake Time (s): Stipulate a time, t, to calculate the size of the suppression zone. You can use this alongside or instead of Wake Distance. If both Wake Time and Wake Distance are configured, then the distance used for suppression will be the maximum of the two values.

Wake Range (m): The maximum Wake Distance.

When using Wake Time an expansion factor is included in the calculation that automatically adjusts the size of the wake suppression area based on the size of the target. The calculation used is as follows:

Wake Time * radar update rate * expansion factor

The expansion factor is as follows: 1 = normal size boat, 2 = medium sized boat, 4 = large boat

Because the Wake Time is based on the radar update rate it means that a value of 1 does not necessarily mean 1 second. For example if you are using a 2Hz radar than a wake time of 2 would actually be 1 second. If using a 1Hz radar then a value of 2 would be 2 seconds.

Shadow Suppression

Shadow Angle (°): θ , Theta. The angle of the 'shadow' cast by the track obscuring the beam of the radar.

Shadow Distance (m): x, the length of the shadow.

Note that if you set the Shadow Angle to 0 (zero) then the angle will be automatically set based on the size the target. This is the default and recommended setting.

Proximity Time Suppression

Track Margin Time (s): Time (t) in seconds. Time x velocity (v) = distance ( x ) in metres. Velocity is speed, with the unit of m/s.

Tracking Areas

Area: Select one of the Areas from the list located in the Configuration Tree.

Parameter: Select the Tracking Parameter from the Configuration Tree.

Related Information

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