cvmeas
Measurement function for constant-velocity motion model
Syntax
Description
returns the expected measurement for a state based on the constant-velocity
motion model. You can also use it as a measurement function in a Kalman filter.
The measurement
= cvmeas(state
)state
argument specifies the current state.
also specifies the measurement coordinate system,
measurement
= cvmeas(state
,frame
)frame
.
also specifies the sensor position, measurement
= cvmeas(state
,frame
,sensorpos
)sensorpos
.
also specifies the sensor velocity, measurement
= cvmeas(state
,frame
,sensorpos
,sensorvel
)sensorvel
.
specifies the measurement parameters,
measurement
= cvmeas(state
,measurementParameters
)measurementParameters
.
[
returns the measurement bounds, used by a tracking filter (measurement
,bounds
] = cvmeas(___)trackingEKF
or trackingUKF
) in residual calculations. See the
HasMeasurementWrapping
of the filter object for more
details.
Examples
Create Measurement from Constant-Velocity Object in Rectangular Frame
Define the state of an object in 2-D constant-velocity motion. The state is the position and velocity in both dimensions. The measurements are in rectangular coordinates.
state = [1;10;2;20]; measurement = cvmeas(state)
measurement = 3×1
1
2
0
The z-component of the measurement is zero.
Create Measurement from Constant Velocity Object in Spherical Frame
Define the state of an object in 2-D constant-velocity motion. The state is the position and velocity in each spatial dimension. The measurements are in spherical coordinates.
state = [1;10;2;20];
measurement = cvmeas(state,'spherical')
measurement = 4×1
63.4349
0
2.2361
22.3607
The elevation of the measurement is zero and the range rate is positive. These results indicate that the object is moving away from the sensor.
Create Measurement from Constant-Velocity Object in Translated Spherical Frame
Define the state of an object in 2-D constant-velocity motion. The state consists of position and velocity in each spatial dimension. The measurements are in spherical coordinates with respect to a frame located at (20;40;0) meters.
state = [1;10;2;20];
measurement = cvmeas(state,'spherical',[20;40;0])
measurement = 4×1
-116.5651
0
42.4853
-22.3607
The elevation of the measurement is zero and the range rate is negative. These results indicate that the object is moving toward the sensor.
Create Measurement from Constant-Velocity Object Using Measurement Parameters
Define the state of an object in 2-D constant-velocity motion. The state consists of position and velocity in each spatial dimension. The measurements are in spherical coordinates with respect to a frame located at (20;40;0) meters.
state2d = [1;10;2;20];
frame = 'spherical';
sensorpos = [20;40;0];
sensorvel = [0;5;0];
laxes = eye(3);
measurement = cvmeas(state2d,frame,sensorpos,sensorvel,laxes)
measurement = 4×1
-116.5651
0
42.4853
-17.8885
The elevation of the measurement is zero and the range rate is negative. These results indicate that the object is moving toward the sensor.
Put the measurement parameters in a structure and use the alternative syntax.
measparm = struct('Frame',frame,'OriginPosition',sensorpos,'OriginVelocity',sensorvel, ... 'Orientation',laxes); measurement = cvmeas(state2d,measparm)
measurement = 4×1
-116.5651
0
42.4853
-17.8885
Display Residual Wrapping Bounds for cvmeas
Specify a 2-D state and specify a measurement structure such that the function outputs azimuth, range, and range-rate measurements.
state = [10 1 10 1]'; % [x vx y vy]' mp = struct("Frame","Spherical", ... "HasAzimuth",true, ... "HasElevation",false, ... "HasRange",true, ... "HasVelocity",false);
Output the measurement and wrapping bounds using the cvmeas
function.
[measure,bounds] = cvmeas(state,mp)
measure = 2×1
45.0000
14.1421
bounds = 2×2
-180 180
-Inf Inf
Input Arguments
state
— Current state
real-valued 2D-by-N matrix
Current state for constant-velocity motion, specified as a real-valued
2D-by-N matrix.
D is the number of spatial degrees of freedom of
motion and N is the number states. The
state
is expected to be Cartesian state. For each
spatial degree of motion, the state vector, as a column of the
state
matrix, takes the form shown in this
table.
Spatial Dimensions | State Vector Structure |
---|---|
1-D | [x;vx] |
2-D | [x;vx;y;vy] |
3-D | [x;vx;y;vy;z;vz] |
For example, x
represents the
x-coordinate and vx
represents the
velocity in the x-direction. If the motion model is 1-D,
values along the y and z axes are
assumed to be zero. If the motion model is 2-D, values along the
z axis are assumed to be zero. Position coordinates
are in meters and velocity coordinates are in meters/sec.
Example: [5;.1;0;-.2;-3;.05]
Data Types: single
| double
frame
— Frame to report measurements
'rectangular'
(default) | 'spherical'
Frame to report measurements, specified as 'rectangular'
or
'spherical'
. When you specify frame as
'rectangular'
, a measurement consists of x,
y, and z Cartesian coordinates. When you
specify frame as 'spherical'
, a measurement consists of azimuth,
elevation, range, and range rate.
Data Types: char
| string
sensorpos
— Sensor position
[0;0;0]
(default) | real-valued 3-by-1 column vector
Sensor position with respect to the navigation frame, specified as a real-valued 3-by-1 column vector. Units are in meters.
Data Types: single
| double
sensorvel
— Sensor velocity
[0;0;0]
(default) | real-valued 3-by-1 column vector
Sensor velocity with respect to the navigation frame, specified as a real-valued 3-by-1 column vector. Units are in m/s.
Data Types: single
| double
laxes
— Local sensor axes coordinates
[1,0,0;0,1,0;0,0,1]
(default) | 3-by-3 orthogonal matrix
Local sensor axes coordinates, specified as a 3-by-3 orthogonal matrix. Each column specifies the direction of the local x-, y-, and z-axes, respectively, with respect to the navigation frame. The matrix is the rotation matrix from the global frame to the sensor frame.
Data Types: single
| double
measurementParameters
— Measurement parameters
structure | array of structures
Measurement parameters, specified as a structure or an array of structures. This table lists the fields in the structure.
Field | Description | Example |
---|---|---|
Frame | Frame used to report measurements, specified as one of these values:
Tip In Simulink, when you create an object detection Bus, specify
| 'spherical' |
OriginPosition | Position offset of the origin of the frame relative to the parent frame, specified as an [x y z] real-valued vector. | [0 0 0] |
OriginVelocity | Velocity offset of the origin of the frame relative to the parent frame, specified as a [vx vy vz] real-valued vector. | [0 0 0] |
Orientation | Frame rotation matrix, specified as a 3-by-3 real-valued orthonormal matrix. | [1 0 0; 0 1 0; 0 0 1] |
HasAzimuth | Logical scalar indicating if azimuth is included in the measurement. This
field is not relevant when the | 1 |
HasElevation | Logical scalar indicating if elevation information 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 |
HasRange | Logical scalar indicating if range is included in the measurement. This
field is not relevant when the | 1 |
HasVelocity | Logical scalar indicating if the reported detections include velocity measurements. For a
measurement reported in the rectangular frame, if HasVelocity
is false , the measurements are reported as [x y
z] . If HasVelocity is true ,
the measurement is reported as [x y z vx vy vz] . For a
measurement reported in the spherical frame, if HasVelocity
is true , the measurement contains range-rate
information. | 1 |
IsParentToChild | Logical 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 |
If you want to perform only one coordinate transformation, such as a transformation from the body frame to the sensor frame, you must specify a measurement parameter structure. If you want to perform multiple coordinate transformations, you must specify an array of measurement parameter structures. To learn how to perform multiple transformations, see the Convert Detections to objectDetection Format (Sensor Fusion and Tracking Toolbox) example.
Data Types: struct
Output Arguments
measurement
— Measurement of state
real-valued N-element row vector | real-valued M-by-N matrix
Measurement vector, returned as an N-element real-valued row vector or an M-by-N real-valued matrix. M, the size of each measurement, can vary depending on the syntax. For more information, see the following table. N, the number of measurements, is the same as the number of states. The format of the measurement vector depends on the syntax.
When you do not specify the
measurementParameters
argument and set theframe
argument to'rectangular'
, the function outputs measurement vectors in the format of[x;y;z]
.When you do not specify the
measurementParameters
argument and set theframe
argument to'spherical'
, the function outputs measurement vectors in the format of[az;el;r;rr]
.When you specify the
measurementParameters
argument and set theframe
field to'rectangular'
, the size of the measurement vector depends on the value of theHasVelocity
field in themeasurementParameters
structure. The measurement vector includes the Cartesian position and velocity coordinates of the tracked object with respect to the ego vehicle coordinate system.Rectangular Measurements
HasVelocity
='false'
[x;y;z]
HasVelocity
='true'
[x;y;z;vx;vy;vz]
Position units are in meters and velocity units are in m/s.
When you specify the
measurementParameters
argument and set theframe
field to'spherical'
, the size of the measurement vector depends on the value of theHasVelocity
,HasRange
, andHasElevation
fields in themeasurementParameters
structure. The measurement vector includes the azimuth angle, az, elevation angle, el, range, r, and range rate, rr, of the object with respect to the local ego vehicle coordinate system. Positive values for range rate indicate that an object is moving away from the sensor.Spherical Measurements
HasRange
='true'
HasRange
='false'
HasElevation
='false'
HasElevation
='true'
HasElevation
='false'
HasElevation
='true'
HasVelocity
='false'
[az;r]
[az;el;r]
[az]
[az;el]
HasVelocity
='true'
[az;r;rr]
[az;el;r;rr]
[az]
[az;el]
Angle units are in degrees, range units are in meters, and range rate units are in m/s.
Data Types: double
bounds
— Measurement residual wrapping bounds
real-valued two-element row vector | M-by-2 real-valued matrix
Measurement residual wrapping bounds, returned as a two-element real-valued row vector or an
M-by-2 real-valued matrix, where M is the size of each
measurement. Each row of the matrix corresponds to the lower and upper bounds, respectively,
of each measurement in the measurement
output.
The function returns different bound values based on the frame
input.
If you specify
frame
as'Rectangular'
, each row of the matrix is[-Inf Inf]
, indicating that the filter did not wrap the measurement residual.
If you specify
frame
as'Spherical'
, the function returns bounds for each measurement based on the following:When
HasAzimuth
=true
, the matrix includes a row of[-180 180]
, indicating that the filter wrapped the azimuth residual in the range of[-180 180]
in degrees.When
HasElevation
=true
, the matrix includes a row of[-90 90]
, indicating that the filter wrapped the elevation residual in the range of[-90 90]
in degrees.When
HasRange
=true
, the matrix includes a row of[-Inf Inf]
, indicating that the filter did not wrap the range residual.When
HasVelocity
=true
, the matrix includes a row of[-Inf Inf]
, indicating that the filter did not wrap the range rate residual.
If you set any of the fields to false
, the returned
bounds
do not contain the corresponding row. For example, if
HasAzimuth
= true
, HasElevation
=
false
, HasRange
= true
,
HasVelocity
= true
, then the function returns the
bounds as:
-180 180 -Inf Inf -Inf Inf
The filter wraps the measuring residuals based on this equation:
where x is the residual to wrap, a is the lower bound, b is the upper bound, mod is the remainder after division, and xwrap is the wrapped residual.
Data Types: single
| double
More About
Azimuth and Elevation Angle Definitions
The azimuth angle of a vector is the angle between the x-axis and its orthogonal projection onto the xy-plane. The angle is positive when going from the x-axis toward the y-axis. Azimuth angles lie between –180 and 180 degrees. The elevation angle is the angle between the vector and its orthogonal projection onto the xy-plane. The angle is positive when going toward the positive z-axis from the xy-plane.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Version History
Introduced in R2017a
See Also
Functions
constvel
(Sensor Fusion and Tracking Toolbox) |constveljac
(Sensor Fusion and Tracking Toolbox) |cvmeasjac
(Sensor Fusion and Tracking Toolbox) |cameas
|ctmeas
(Sensor Fusion and Tracking Toolbox) |ctrvmeas
(Sensor Fusion and Tracking Toolbox) |singermeas
(Sensor Fusion and Tracking Toolbox) |initcvukf
(Sensor Fusion and Tracking Toolbox) |initcvekf
(Sensor Fusion and Tracking Toolbox)
Objects
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