Documentation

initcapf

Create constant acceleration tracking particle filter from detection report

Description

example

pf = initcapf(detection) initializes a constant acceleration particle filter for object tracking based on information provided in an objectDetection object, detection.

Examples

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Create a constant acceleration tracking particle filter object, trackingPF, from an initial detection report. The detection report is made from an initial 3-D position measurement of the particle filter state in rectangular coordinates. You can obtain the 3-D position measurement using the constant acceleration measurement function, cameas.

This example uses the coordinates, x = 1, y = 3, z = 0 and a 3-D position measurement noise of [1 0.2 0; 0.2 2 0; 0 0 1].

detection = objectDetection(0, [1;3;0], 'MeasurementNoise', [1 0.2 0; 0.2 2 0; 0 0 1]);

Use initcapf to create a trackingPF filter initialized at the provided position and using the measurement noise defined above.

pf = initcapf(detection)
pf =
trackingPF with properties:

State: [9⨯1 double]
StateCovariance: [9⨯9 double]
IsStateVariableCircular: [0 0 0 0 0 0 0 0 0]

StateTransitionFcn: @constacc
ProcessNoiseSamplingFcn: []
ProcessNoise: [3x3 double]

MeasurementFcn: @cameas
MeasurementLikelihoodFcn: []
MeasurementNoise: [3x3 double]

Particles: [9x1000 double]
Weights: [1x1000 double]
ResamplingPolicy: [1x1 trackingResamplingPolicy]
ResamplingMethod: 'multinomial'

Check the values of the state and the measurement noise. Verify that the filter state, pf.State, has approximately the same position components as the detection measurement, detection.Measurement.

pf.State
ans = 9×1

0.9674
0.3690
0.3827
3.0317
0.3056
-0.5904
0.0038
0.0411
-0.6815

Verify that the filter measurement noise, pf.MeasurementNoise, is the same as the detection.MeasurementNoise values.

pf.MeasurementNoise
ans = 3×3

1.0000    0.2000         0
0.2000    2.0000         0
0         0    1.0000

Create a constant acceleration tracking particle filter object, trackingPF, from an initial detection report. The detection report is made from an initial 3-D position measurement of the particle filter state in spherical coordinates. You can obtain the 3-D position measurement using the constant acceleration measurement function, cameas.

This example uses the coordinates, az = 30, e1 = 5, r = 100, rr = 4 and a measurement noise of diag([2.5, 2.5, 0.5, 1].^2).

meas = [30;5;100;4];
measNoise = diag([2.5, 2.5, 0.5, 1].^2);

Use the MeasurementParameters property of the detection object to define the frame. When not defined, the fields of the MeasurementParameters struct use default values. In this example, sensor position, sensor velocity, orientation, elevation, and range rate flags are default.

measParams = struct('Frame','spherical');
detection = objectDetection(0,meas,'MeasurementNoise',measNoise,...
'MeasurementParameters',measParams)
detection =
objectDetection with properties:

Time: 0
Measurement: [4x1 double]
MeasurementNoise: [4x4 double]
SensorIndex: 1
ObjectClassID: 0
MeasurementParameters: [1x1 struct]
ObjectAttributes: {}

Use initcapf to create a trackingPF filter initialized at the provided position and using the measurement noise defined above.

pf = initcapf(detection)
pf =
trackingPF with properties:

State: [9⨯1 double]
StateCovariance: [9⨯9 double]
IsStateVariableCircular: [0 0 0 0 0 0 0 0 0]

StateTransitionFcn: @constacc
ProcessNoiseSamplingFcn: []
ProcessNoise: [3x3 double]

MeasurementFcn: @cameas
MeasurementLikelihoodFcn: []
MeasurementNoise: [4x4 double]

Particles: [9x1000 double]
Weights: [1x1000 double]
ResamplingPolicy: [1x1 trackingResamplingPolicy]
ResamplingMethod: 'multinomial'

Verify that the filter state produces approximately the same measurement as detection.Measurement.

meas2 = cameas(pf.State, detection.MeasurementParameters)
meas2 = 4×1

29.9188
5.0976
99.8303
4.0255

Input Arguments

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Detection report, specified as an Object Detections object.

Example: detection = objectDetection(0,[1;4.5;3],'MeasurementNoise', [1.0 0 0; 0 2.0 0; 0 0 1.5])

Output Arguments

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Constant acceleration particle filter for object tracking, returned as a trackingPF object.

Algorithms

• The function configures the filter with 1000 particles. In creating the filter, the function computes the process noise matrix assuming a unit standard deviation for the acceleration change rate.

• You can use this function as the FilterInitializationFcn property of trackerTOMHT and trackerGNN System objects.

Extended Capabilities

System Objects

Introduced in R2018b

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