Point-based Zone

This security zone type is available on the QbProtect product.

The point-based security zone utilizes changes in the number of detected points within the zone’s cuboid to generate an alarm.

Application

Basic alarm generation

Whenever the scene does not allow for intruders to be detected as objects (e.g, the visibility is very poor or the objects' shape can vary) this zone can utilize the raw point information to generate an intrusion alarm.

The simplicity of the approach can lead to cumbersome parameterization and a significant number of false alarms. Using the object-based security zone is recommended.

Parameters

See configuration API definition.

Intrusion conditions

Minimum points (default: 15)

The lower threshold of tolerated points in the zone. When the number of detected points exceeds the configured value, an alarm will be raised.

Maximum points (default: 0)

The upper threshold of points in the zone. When set to zero, the upper threshold is disabled. When set to a nonzero value, the parameter must also be larger than the lower threshold. When the number of detected points exceeds the upper threshold, the alarm is disabled.

Minimum intruding duration (default: 0, unit: \(s\))

The duration for which all intrusion conditions have to be met until an alarm is raised. A value of 0 (the default) raises the alarm immediately upon first detection.

Intrusion confidence (default: 100, unit: \(\%\))

The confidence threshold for raising an alarm. The current confidence value is computed over the time interval specified as the minimum intruding duration. A value of \(100\%\) ensures, that all intrusion conditions are met in all observations within the minimum intruding duration. Values lower than \(100\%\) make alarm generation more sensitive by allowing the configured ratio of observations within the minimum intruding duration window where all intrusion conditions are met.

The intrusion confidence is only configurable when the minimum intruding duration is nonzero.

Output options

Hold duration (default: 0, unit: \(s\)): Minimum hold time for the alarm when active. A value of 0 (default) will disable the alarm as soon as the conditions for raising the alarm are no longer met.
Linked occupancy zones (default: empty list): List of occupancy zones. Evaluation of this zone is skipped when any of the occupancy zones are occupied. The default value (empty list) will always trigger the zone’s measurement.

Tampering

Minimum coverage (default: 0, unit: \(\%\)): The minimum percentage of the zone’s volume visible to the sensor. An object between the sensor and the zone can obstruct the visibility so that less than the specified percentage of the zone’s volume is seen by the sensor. In this case a tampering alarm is generated to indicate, that the zone’s intrusion state can not be properly evaluated anymore. The underlying calculation is based on the amount of unobstructed laser rays being able to penetrate the zone (ray casting). The default value of 0 will never raise the zone tampering alarm, even when the zone is fully obstructed. Note that a zone which configures a minimum coverage must also set a hold duration of at least 3 seconds, otherwise it is rejected.

This per zone measurement is how a covered device is detected whenever at least one zone configures a minimum coverage. If no zone does, there is nothing to measure per zone and the device falls back to the legacy signal, which evaluates the rate of points the whole device returns and reports a single verdict for it — that verdict cannot tell which zone can no longer be evaluated. The two are mutually exclusive, and because the zones carrying a coverage alarm are exactly the ones replicated to the followers, every sensor of a swarm always uses the same one.

In a swarm every sensor measures its own coverage of the zone and the leader decides over all of them: the alarm is only raised once every sensor observing the zone is below the configured minimum coverage. A zone which one sensor can no longer see, but another still can, is not tampered — its intrusion state can still be evaluated. Sensors which barely reach the zone do not take part in the decision, so a sensor which only clips a corner of it cannot suppress the alarm of one whose view is fully obstructed.

Algorithm

The algorithm uses its enclosed portion of the foreground point cloud as input data. It operates in two stages:

Count points

The number of points inside the zone’s cuboid are counted. To avoid randomly jumping or flickering values, the current number of points is filtered by applying a moving-average and a hysteresis-step filter:

MovingAverage: Average value from the last three observations.
HysteresisStep: Only update the counted number of points when the delta is larger than \(10\%\) of the minimum points or more than \(10\) points in total.

The filtered value is matched against the minimum and maximum number of points values configured in the intrusion conditions to set the intrusion state accordingly.

Alarm filtering

Based on the intrusion state, the actual alarm state is determined. In this step, the configuration values for the minimum intruding duration and the intrusion confidence are applied.

Output data

See full API definition.

State

alarm (\(true,false\)): The current alarm. A \(true\) value indicates an alarm.
intrusion: Unfiltered pre-alarm state from the zone’s internal alarm logic.
number of detected points: Number of points currently detected inside the zone.
point cloud: Point cloud which triggered the alarm. This field is only set while an alarm is active.
intrusion confidence: Current confidence based on the minimum intruding duration window.