Introduction

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

For more information regarding the function and process of debris detection please refer to Debris Detection.

Contents

Processes

Open

Use Debris Channel: Select to enable the Debris Channel.

Clutter Map

Open

Clutter Map Time (%): The system take a percentage of the incoming signal and adds it to the Clutter Map.

Clutter Start Up Delay (m): The time after start-up before the system processes further data. This helps with clutter occlusion and also helps speed up the start-up.

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: This is the minimum value the clutter can drop to.

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.

Thresholding

Threshold Delta: This threshold works in exactly the same way as for normal processing, but it only applies to the debris channel. The threshold output is always levels above, therefore there are the normal area dependent threshold settings in the Debris Default tracking parameters, however we would encourage you to only use this global threshold setting. If you increase this value, you will desensitise the detection, decreasing the value will increase sensitivity and therefore increase the likelihood of nuisance alarms.

Threshold Window: 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.

Scan to Scan Integration

Full Window Size (m) (hits): This provides the total number of scans used to examine a signal to establish whether we think it is debris. In the worst case this may lead to a 4 second delay in detecting debris, but this process is essential to detect small targets with any level of confidence. Increasing this window size will delay detection and potentially reduce false alarms. The disadvantage of delaying detection is that more of the target will become absorbed into the clutter map and therefore become harder to detect over time. This setting is linked to the Recent Window Size and the Hit Counts - they should all be considered when making changes to the configuration. The process will be looking for the Full Hit Count Threshold being exceeded within this window. For example, with a Full Window Size of 16 and a Full Hit Count Threshold of 10, we would expect our debris signal to appear above threshold 10/16 scans.

Recent Window Size (m) (hits): This window provides the total number of scan to analyse within the last n of the Full Window Size. This allows us to specify a level of confidence that indicates the same signal we saw at the beginning of the Full Window is still there by the end of the Full Window scan period. For example, if the Full Window Size is 16 and the Recent Window Size is 6 then this means use the last 6 scans (i.e. 11 - 16) of the full window as the recent window. Within this recent window we look for a further hit threshold using the Recent Hit Count Threshold. This has to be exceeded along with the Full Hit Count Threshold for the detection to be considered genuine debris. Increasing this value will typically indicate you expect more threshold hits over a larger proportion of the Full Window scan. Decreasing this value indicates you are focusing on hits at the very end of the scan period.

Full Hit Count: This is the total number of times we expect the threshold to be exceeded within the specified Full Window Size. If the Full Window Size is 16 and the Full Hit Count is 10, then we need to see a total of 10 hits in 16 scans to consider the target as debris.

Recent Hit Count: This is the total number of times we expect the threshold to be exceeded within the specified Recent Window Size. If the Recent Window Size is 6, and the Recent Hit Count is 3, then we need to see a total of 3 hits in last 6 scans to consider the target as debris.

Integration Threshold (pwr): This is the threshold for input video to be considered as significant for integration. If the video exceeds this threshold then it is integrated. When used with the Dynamic Threshold process configured, set this threshold to 0. The purpose of the threshold process is to decide if each video sample is “of interest” for further processing by comparing the video intensity to a threshold level. If the video sample exceeds the threshold then it is passed on. If it does not exceed the threshold the video sample is rejected. The thresholding process compares each video sample to a background threshold. The background threshold is calculated for each sample and reflects the local video distribution around the test sample.

Instant Threshold (pwr): Instant threshold allows cells of sufficient signal strength to bypass the SSI (scan to scan integration) process. So any cell with a strength above the Instant Threshold will immediately be made available for plot extraction.

Recursive Average Gain: The gain used when implementing a rolling average of the amplitude values of real cells seen during the SSI process. By default the SSI process does not provide the real signal strength of a target, instead it provides a synthetic value based on the numbers of times its been seen. By using setting the gain value we can receive the rolling average of the real target signal from multiple sightings. The gain controls how much of a new cell's amplitude is added to the rolling average.

Plot Extraction

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

Merge Plots: 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 larger plots using the method selected in the Mode setting.

Mode:

None: No plot merging.

Azimuth: Merges in azimuth. This option provides good performance for highway monitoring due to the fixed movement of vehicles in straight lines past the radar.

Distance: Merges in range distance (along the radius).

Shape Distance: Merges in azimuth and range. Attempts to draw a containing boundary around relevant plots. This is a good general purpose option and works well for most situations.

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.

Tracking

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

Tracking Areas

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

Parameter: Select the Tracking Parameter from the list located in the Configuration Tree.

Editing Multiple Radar

When highlighting more than one radar in the list within the radar dialog there will be the following selected values to edit:

Channel

Update Debris: Select this option to edit the channel settings marked with a * in the fields below:

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.

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

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.

Full Window Size* (m) (hits): This provides the total number of scans used to examine a signal to establish whether we think it is debris. In the worst case this may lead to a 4 second delay in detecting debris, but this process is essential to detect small targets with any level of confidence. Increasing this window size will delay detection and potentially reduce false alarms. The disadvantage of delaying detection is that more of the target will become absorbed into the clutter map and therefore become harder to detect over time. This setting is linked to the Recent Window Size and the Hit Counts - they should all be considered when making changes to the configuration. The process will be looking for the Full Hit Count Threshold being exceeded within this window. For example, with a Full Window Size of 16 and a Full Hit Count Threshold of 10, we would expect our debris signal to appear above threshold 10/16 scans.

Recent Window Size* (m) (hits): This window provides the total number of scan to analyse within the last n of the Full Window Size. This allows us to specify a level of confidence that indicates the same signal we saw at the beginning of the Full Window is still there by the end of the Full Window scan period. For example, if the Full Window Size is 16 and the Recent Window Size is 6 then this means use the last 6 scans (i.e. 11 - 16) of the full window as the recent window. Within this recent window we look for a further hit threshold using the Recent Hit Count Threshold. This has to be exceeded along with the Full Hit Count Threshold for the detection to be considered genuine debris. Increasing this value will typically indicate you expect more threshold hits over a larger proportion of the Full Window scan. Decreasing this value indicates you are focusing on hits at the very end of the scan period.

Full Hit Count*: This is the total number of times we expect the threshold to be exceeded within the specified Full Window Size. If the Full Window Size is 16 and the Full Hit Count is 10, then we need to see a total of 10 hits in 16 scans to consider the target as debris.

Recent Hit Count*: This is the total number of times we expect the threshold to be exceeded within the specified Recent Window Size. If the Recent Window Size is 6, and the Recent Hit Count is 3, then we need to see a total of 3 hits in last 6 scans to consider the target as debris.

Recursive Average Gain*: The gain used when implementing a rolling average of the amplitude values of real cells seen during the SSI process. The gain controls how much of a new cell's amplitude is added to the rolling average.

Global

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.

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

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.

Distribute Tracks: Select this to display the tracks on the PPI carriageway. 

Layer: The layer of the PPI display on which the radar is active.

Group: Which radar group this radar belongs to e.g. Default Radar Group.

Hide: Select this to make the radar unselectable and translucent in appearance on the PPI. This allows you to simplify the clutter within the site map by concealing this item while leaving it working as usual. It can still be selected within the Configuration Tree - it will be temporarily revealed within the site map.

X and Y Offset Delta (m): These are X and Y offset deltas that are applied to the position of all the selected radar. For example, if you provided an X delta of +10m then all the selected radar would move east by 10m from their current location.

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