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objectDetection

Report for single object detection

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Description

An objectDetection object contains an object detection report that was obtained by a sensor for a single object. You can use the objectDetection output as the input to trackers such as multiObjectTracker.

Creation

Syntax

detection = objectDetection(time,measurement)
detection = objectDetection(___,Name,Value)

Description

example

detection = objectDetection(time,measurement) creates an object detection at the specified time from the specified measurement.

Tip

To create an empty objectDetection object, use objectDetection.empty().

example

detection = objectDetection(___,Name,Value) creates a detection object with properties specified as one or more Name,Value pair arguments. Any unspecified properties have default values. You cannot specify the Time or Measurement properties using Name,Value pairs.

Input Arguments

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Detection time, specified as a nonnegative real scalar. This argument sets the Time property.

Object measurement, specified as a real-valued N-element vector. N is determined by the coordinate system used to report detections and other parameters that you specify in the MeasurementParameters property for the objectDetection object.

This argument sets the Measurement property.

Output Arguments

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Detection report for a single object, returned as an objectDetection object. An objectDetection object contains these properties:

PropertyDefinition
TimeMeasurement time
MeasurementObject measurements
MeasurementNoiseMeasurement noise covariance matrix
SensorIndexUnique ID of the sensor
ObjectClassIDObject classification
MeasurementParametersParameters used by initialization functions of nonlinear Kalman tracking filters
ObjectAttributesAdditional information passed to tracker

Properties

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Detection time, specified as a nonnegative real scalar. You cannot set this property as a name-value pair. Use the time input argument instead.

Example: 5.0

Data Types: double

Object measurement, specified as a real-valued N-element vector. You cannot set this property as a name-value pair. Use the measurement input argument instead.

Example: [1.0;-3.4]

Data Types: double | single

Measurement noise covariance, specified as a scalar or a real positive semi-definite symmetric N-by-N matrix. N is the number of elements in the measurement vector. For the scalar case, the matrix is a square diagonal N-by-N matrix having the same data interpretation as the measurement.

Example: [5.0,1.0;1.0,10.0]

Data Types: double | single

Sensor identifier, specified as a positive integer. The sensor identifier lets you distinguish between different sensors and must be unique to the sensor.

Example: 5

Data Types: double

Object class identifier, specified as a nonnegative integer. Use this property to distinguish detections generated from different kinds of objects. For example, use 1 for objects of type "car", and 2 for objects of type "pedestrian". The value 0 denotes an unknown object type.

When you specify this property as a nonzero integer, you can use the ObjectClassParameters property to specify the detection classifier statistics.

Example: 1

Data Types: double

Parameters for detection classifier, specified as a structure. The structure can contain any field. For class fusion with a multi-object tracker, such as the trackerGNN (Sensor Fusion and Tracking Toolbox) System object, you can specify the ConfusionMatrix field as follows.

Field NameDescription
ConfusionMatrix

Confusion matrix of the detection classifier, specified as an N-by-N real-valued matrix, where N is the number of possible object classes. The (i,j) element of the matrix represents the weight or probability that the classifier classifies the detection as class j if the true class of the detection is class i.

For example, if the classifier outputs two classes and makes right classification 95% of the time, specify this matrix as [0.95 0.05; 0.05 0.95].

Data Types: struct

Measurement function parameters, specified as a structure array, a cell containing a structure array, or a cell array. The property contains all the arguments used by the measurement function specified by the MeasurementFcn property of a nonlinear tracking filter such as trackingEKF or trackingUKF.

The table shows sample fields for the MeasurementParameters structures.

FieldDescriptionExample
Frame

Frame used to report measurements, specified as one of these values:

  • 'rectangular' — Detections are reported in rectangular coordinates.

  • 'spherical' — Detections are reported in spherical coordinates.

'spherical'
OriginPositionPosition offset of the origin of the frame relative to the parent frame, specified as an [x y z] real-valued vector.[0 0 0]
OriginVelocityVelocity offset of the origin of the frame relative to the parent frame, specified as a [vx vy vz] real-valued vector.[0 0 0]
OrientationFrame rotation matrix, specified as a 3-by-3 real-valued orthonormal matrix.[1 0 0; 0 1 0; 0 0 1]
HasAzimuthLogical scalar indicating if azimuth is included in the measurement.1
HasElevationLogical scalar indicating if elevation is included in the measurement. For measurements reported in a rectangular frame, and if HasElevation is false, the reported measurements assume 0 degrees of elevation.1
HasRangeLogical scalar indicating if range is included in the measurement.1
HasVelocityLogical scalar indicating if the reported detections include velocity measurements. For measurements reported in the rectangular frame, if HasVelocity is false, the measurements are reported as [x y z]. If HasVelocity is true, measurements are reported as [x y z vx vy vz].1
IsParentToChildLogical scalar indicating if Orientation performs a frame rotation from the parent coordinate frame to the child coordinate frame. When IsParentToChild is false, then Orientation performs a frame rotation from the child coordinate frame to the parent coordinate frame.0

Object attributes passed through the tracker, specified as a cell array. These attributes are added to the output of the multiObjectTracker but not used by the tracker.

Example: {[10,20,50,100],'radar1'}

Examples

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Open Live Script

Create a detection from a position measurement. The detection is made at a timestamp of one second from a position measurement of [100;250;10] in Cartesian coordinates.

detection = objectDetection(1,[100;250;10])
detection = 
  objectDetection with properties:

                     Time: 1
              Measurement: [3x1 double]
         MeasurementNoise: [3x3 double]
              SensorIndex: 1
            ObjectClassID: 0
    ObjectClassParameters: []
    MeasurementParameters: {}
         ObjectAttributes: {}
Open Live Script

Create an objectDetection from a time and position measurement. The detection is made at a time of one second for an object position measurement of [100;250;10]. Add measurement noise and set other properties using Name-Value pairs.

detection = objectDetection(1,[100;250;10],'MeasurementNoise',10, ...
    'SensorIndex',1,'ObjectAttributes',{'Example object',5})
detection = 
  objectDetection with properties:

                     Time: 1
              Measurement: [3x1 double]
         MeasurementNoise: [3x3 double]
              SensorIndex: 1
            ObjectClassID: 0
    ObjectClassParameters: []
    MeasurementParameters: {}
         ObjectAttributes: {'Example object'  [5]}

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2017a

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See Also

Objects