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Introduction

This page details the settings available for the tracker within the Advanced Settings tab.

Contents

Processes

Use STC: Select this to enable Sensitivity Time Control to reduce clutter from nearby static objects. STC helps to reduce clutter by selectively attenuating the radar signal power, within a specified range, to allow for nearby interfering factors, such as buildings, gantries, lakes etc.

Show STC Range: Select to show the STC Range.

Use FTC: Select this for the tracker to use a Fast Time Constant high-pass filter to help reduce the impact of rain on radar results. This is to be used in exceptional circumstances.

Use Clutter Map: Select this for the tracker to use the saved clutter map.

Use Clutter Guard: This adds a margin of error to established clutter in order to avoid false alarms being created from real-time fluctuations in signal return.

Use Azimuth Blanking: Select this to remove all raw radar data from the processing chain behind large returns close to the radar, to avoid unnecessary false alarms. If a track is a certain size at a certain range, we reduce the target shadow to limit false recording by removing signals in the shadow of large targets. Under normal circumstances, we would want to look for multiple targets in the same azimuth, however, when we have large targets very close to the radar, this prevents us detecting anything behind them. In this scenario it is safer to dynamically suppress potential targets, but only for as long as it takes the large target to move out of range.

Use Static Target Detection: Select this to protect long-stationary targets from being absorbed into the clutter map.

Thresholding

Threshold Delta (pwr): Defines the threshold above which the signal will be included for track processing. Signal levels below this threshold will be discarded. Setting a lower threshold value provides greater detection capability but can correspondingly increase the level of false alarms.

Threshold Window (m): The moving window size over which to calculate the dynamic threshold. The noise is averaged over this window size and the threshold delta is applied to this averaged value to check for significant power returns.

Threshold Output Value: Defines the value that will be sent through to the tracker when a radar input signal exceeds the Threshold Delta value and how the input signal from that radar should be conditioned before being passed on to the next stage.

Input Value: Passes on the radar signal unchanged, so the total amplitude of each signal wave is recorded.

Level Above Threshold: Subtracts the Threshold value from the radar signal to isolate only the signal that exceeds the threshold.

Full Scale: Converts any signal that exceeds the Threshold essentially into a binary signal (i.e. either zero or the maximum value).

SD Factor: A factor used to clean up the process data by using the standard deviation of the local threshold data.

STC

Range: Defines the distance up to which the attenuation specified in the Power Factor field should be applied.

Start Range: Defines the distance from the radar to the point at which the Power Factor increase is triggered. In the graph below, it is hatched in green.

Power Factor (%): Determines the attenuation that should be applied to operation within the distance to local objects that are specified in the STC Range field.

Once the Use STC option is selected, the tracker will apply the chosen Power Factor after the start range, and scale up (in linear fashion) to 100% of the stated STC Range. As a result, the effect of nearby objects is reduced.

This is especially useful when the radar is near water, to reduce signal reflection.

FTC

FTC Range (m): Defines the width of the high-pass filter.

FTC Level (0-1): Defines the local average that must be subtracted from the input signal to achieve the high-pass filter.

Clutter Map

The Clutter Map is a record of static, unchanging objects that are within view of the radar sensor. Clutter Maps are created and used as reference points for radar sensors and their trackers so that they can better concentrate on objects that are moving. Please refer to Clutter Map and Clutter Floor for further information.

Clutter Map Time (%): This value dictates how much of the received radar data contributes towards maintaining an accurate Clutter Map and movement analysis. It is measured as a data percentage per revolution of the radar, e.g. for a value of 85%, this means 15% of the data from the scan is used to update the clutter (background radar picture). Therefore 85% of the data is analysed for movement. The higher the number, the more the data is analysed for movement, and the more sensitive it is to movement. Recommended setting is between 80% and 95%.

Clutter Startup Delay (s): This value determines clutter absorption period.

Clutter Slow Decay: The Clutter Slow Decay effects how clutter is removed from the clutter map. It works by adding to the Time Constant (please refer to Tracker) being used in the clutter map. We use a default Time Constant of 90% in the standard tracking clutter map, so the slow decay is a % increase of the remaining 10% from the Time Constant. For example: a 50% Slow Decay is equal to 50% of the 10% that is not used by the clutter channel (so it would be 5%). This is then added to the Time Constant when clutter is being removed, causing the removal of clutter to be slower (essentially being removed at a Time Constant of 95% compared to the previous 90%). This allows us to hold onto the clutter data for longer. An example of this useful feature can be seen in ClearWay™ during situations where queues are in progress. When the queue drops, we often get false tracks where targets, such as trees, become visible to the radar again. By holding the clutter data for longer, there is more time before the clutter value will drop below the threshold, causing an alarm when the clutter jumps back up, once the queue has cleared.

Use Clutter File as Floor: Select this for the tracker will use the saved clutter map as the base template of static objects (to be ignored) within sight of the radar sensor.

Hold Azimuth Multiplier (width) and Hold Range Multiplier (depth): These parameters are used to prevent tracks that become stationary for a period of time from being absorbed into the clutter map. To do this the clutter map process holds open a hole in the clutter map to prevent the clutter building up where the track is. These two parameters define the size of the ‘hole’ as a factor of the reported track size. A value of 1 for both range and azimuth holds an area in range and azimuth that is the same size as the track. If they are both set to 2 then the area would be twice the size of track and so on. Using a value slightly larger than 1 allows for any variation in the reported size of track. It also allows for very small movement when the track is stationary. If both values are set to zero then track holding is disabled.

Clutter Areas

This changes the settings on an area by area basis. Up to 8 Clutter Area Parameters per Clutter Map may be added.

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

Parameters: Select the Clutter Parameter from the Configuration Tree. Please refer to Clutter Parameters for more information.

Clutter Guard

Clutter Guard is used to prevent any fluctuations in the power return due to environmental factors which can change it, and this helps to reduce false alarms. Typically it is used in areas where we don’t expect to see tracks; for example, the central reservation of a motorway. Essentially, it stabilizes the Clutter Map and boosts the signal by amplifying the clutter data within a radar sample.

There are four steps:

  1. Identify the Clutter.

  2. Add a Threshold.

  3. Add a Signal Gain (which is a multiplication of the signal, e.g. 25 x 2) or a Signal Offset (which is a fixed offset e.g. 25 + 20), or both:

  4. Finally add a Signal Spread. For example, with a Signal Spread value of 1, if a clutter signal was 1 bin wide, then the spread would be 1 bin either side of the clutter signal:

Threshold (pwr): This sets the threshold above which the radar samples are considered to be clutter as opposed to noise. This threshold is relative to the median signal strength at each range.

Noise Min Value (pwr): This sets the minimum value which is used to estimate the range dependent clutter. For example any value of zero can be ignored which means this calculation is not skewered by a contour map.

Noise Gain: This sets the gain to apply to the noise component of every radar sample. This effectively amplifies the noise values before the threshold is applied.

Signal Gain: This sets the gain to apply to the clutter component of every radar sample. This effectively amplifies the clutter value.

Signal Offset: This sets the amount of offset applied to the clutter component of every radar sample. This can be used in conjunction or instead of the signal gain.

Signal Spread: This sets how far to spread the signal offset and gain to surrounding samples. This value only applies in range. So, for example, if this value is set to 1 and clutter was detected in sample 10, then the offset and gain would be applied to 9, 10 & 11 (one before and after in range).

The Clutter Guard is to be used with caution because it will reduce detection performance in and around clutter.

Azimuth Blanking

Threshold (pwr): Defines the power of the signal strength.

Maximum Bin: The maximum number of bins (individual cells measured by radars) in which to look for a target above the Threshold.

Bin Tolerance: As the radar azimuth can only see the front of a target, this setting is used to approximate how deep the target is.

Show Blanking: Typically, this setting is only used whilst configuring and testing the Azimuth Blanking, as the radar display will not show the data behind a selected target. On the PPI this would display as a blank segment behind a target when viewing raw data source.

Radar resolution is different for each model, therefore, to calculate Maximum Bins, you need to know the range resolution of the radar.

Azimuth Blanking is a destructive process as it removes data behind the target, whereas Shadow Suppression suppresses the track creation in the shadow of a target but does not remove data.

Static Target Detection

Threshold (%): The minimum % that the live score should be above the base line score.

Base Line Samples: The number of samples to use to calculate the base line score.

Live Samples: The number of samples to use when calculating the live score to compare with the base line.

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