getTrackPositions

Returns updated track positions and position covariance matrix

Syntax

position = getTrackPositions(tracks,positionSelector)
[position,positionCovariances] = getTrackPositions(tracks,positionSelector)

Description

example

position = getTrackPositions(tracks,positionSelector) returns a matrix of track positions. Each row contains the position of a tracked object.

example

[position,positionCovariances] = getTrackPositions(tracks,positionSelector) returns a matrix of track positions.

Examples

collapse all

Create an extended Kalman filter tracker for 3-D constant-velocity motion.

tracker = trackerTOMHT('FilterInitializationFcn',@initcvekf);

Update the tracker with a single detection and get the tracks output.

detection = objectDetection(0,[10;3;-7],'ObjectClassID',3);
tracks = step(tracker,detection,0)
tracks = struct with fields:
             TrackID: 1
            BranchID: 1
          UpdateTime: 0
                 Age: 1
               State: [6x1 double]
     StateCovariance: [6x6 double]
          TrackLogic: 'Score'
     TrackLogicState: [13.7102 13.7102]
         IsConfirmed: 1
           IsCoasted: 0
       ObjectClassID: 3
    ObjectAttributes: {}

Obtain the position vector and position covariance for that track

positionSelector = [1 0 0 0 0 0; 0 0 1 0 0 0; 0 0 0 0 1 0];
[position,positionCovariance] = getTrackPositions(tracks,positionSelector)
position = 1×3

   10.0000    3.0000   -7.0000

positionCovariance = 3×3

    1.0000   -0.0000         0
   -0.0000    1.0000   -0.0000
         0   -0.0000    1.0000

Create an extended Kalman filter tracker for 3-D constant-acceleration motion.

tracker = trackerTOMHT('FilterInitializationFcn',@initcaekf);

Update the tracker with a single detection and get the tracks output.

detection = objectDetection(0,[10;-20;4],'ObjectClassID',3);
tracks = step(tracker,detection,0)
tracks = struct with fields:
             TrackID: 1
            BranchID: 1
          UpdateTime: 0
                 Age: 1
               State: [9x1 double]
     StateCovariance: [9x9 double]
          TrackLogic: 'Score'
     TrackLogicState: [13.7102 13.7102]
         IsConfirmed: 1
           IsCoasted: 0
       ObjectClassID: 3
    ObjectAttributes: {}

Obtain the position vector from the track state.

positionSelector = [1 0 0 0 0 0 0 0 0; 0 0 0 1 0 0 0 0 0; 0 0 0 0 0 0 1 0 0];
position = getTrackPositions(tracks, positionSelector)
position = 1×3

   10.0000  -20.0000    4.0000

Input Arguments

collapse all

Tracked object, specified as a struct array. A track struct array is an array of MATLAB® struct types containing sufficient information to obtain the track position vector and, optionally, the position covariance matrix. At a minimum, the struct must contain a State column vector field and a positive-definite StateCovariance matrix field. For an example of a track struct used by Sensor Fusion and Tracking Toolbox™, examine the output argument, tracks, returned by the step object function of trackerGNN.

Position selector, specified as a D-by-N real-valued matrix of ones and zeros. D is the number of dimensions of the tracker. N is the size of the state vector. Using this matrix, the function extracts track positions from the state vector. Multiply the state vector by position selector matrix returns positions. The same selector is applied to all object tracks.

Output Arguments

collapse all

Positions of tracked objects at last update time, returned as a real-valued M-by-D matrix. D represents the number of position elements. M represents the number of tracks.

Position covariance matrices of tracked objects, returned as a real-valued D-by-D-M array. D represents the number of position elements. M represents the number of tracks. Each D-by-D submatrix is a position covariance matrix for a track.

More About

collapse all

Position Selector for 2-Dimensional Motion

Show the position selection matrix for two-dimensional motion when the state consists of the position and velocity.

[10000010]

Position Selector for 3-Dimensional Motion

Show the position selection matrix for three-dimensional motion when the state consists of the position and velocity.

[100000001000000010]

Position Selector for 3-Dimensional Motion with Acceleration

Show the position selection matrix for three-dimensional motion when the state consists of the position, velocity, and acceleration.

[100000000000100000000000100]

Extended Capabilities

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

Introduced in R2018b