initctckf

Create a turn rate tracking cubature Kalman filter object, trackingCKF, from an initial detection report. The detection report is made from an initial 3-D position measurement of the Kalman filter state in rectangular coordinates. You can obtain the 3-D position measurement using the constant turn rate measurement function, ctmeas.

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 initctckf to create a trackingCKF filter initialized at the provided position and using the measurement noise defined above.

ckf = initctckf(detection)

ckf = 
  trackingCKF with properties:

                          State: [7x1 double]
                StateCovariance: [7x7 double]

             StateTransitionFcn: @constturn
                   ProcessNoise: [4x4 double]
        HasAdditiveProcessNoise: 0

                 MeasurementFcn: @ctmeas
         HasMeasurementWrapping: 1
               MeasurementNoise: [3x3 double]
    HasAdditiveMeasurementNoise: 1

                EnableSmoothing: 0

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

ckf.State

ans = 7×1

     1
     0
     3
     0
     0
     0
     0

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

ckf.MeasurementNoise

ans = 3×3

    1.0000    0.2000         0
    0.2000    2.0000         0
         0         0    1.0000

Create a constant turn rate tracking cubature Kalman filter object, trackingCKF, from an initial detection report. The detection report is made from an initial 3-D position measurement of the Kalman filter state in spherical coordinates. You can obtain the 3-D position measurement using the constant turn rate measurement function, ctmeas.

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
    ObjectClassParameters: []
    MeasurementParameters: [1x1 struct]
         ObjectAttributes: {}

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

ckf = initctckf(detection)

ckf = 
  trackingCKF with properties:

                          State: [7x1 double]
                StateCovariance: [7x7 double]

             StateTransitionFcn: @constturn
                   ProcessNoise: [4x4 double]
        HasAdditiveProcessNoise: 0

                 MeasurementFcn: @ctmeas
         HasMeasurementWrapping: 1
               MeasurementNoise: [4x4 double]
    HasAdditiveMeasurementNoise: 1

                EnableSmoothing: 0

Verify that the filter state produces the same measurement as above.

meas2 = ctmeas(ckf.State, measParams)

meas2 = 4×1

   30.0000
    5.0000
  100.0000
    4.0000