CustomSensor

Custom sensor specification

Since R2025a

Description

A CustomSensor object contains a custom sensor specification. You can modify this specification by defining its measurement model, detectability model, clutter model, and birth model. Use this object as an input to the multiSensorTargetTracker function.

Creation

To create a CustomSensor object, use the trackerSensorSpec function with the input argument "custom". For example:

spec = trackerSensorSpec("custom")

Properties

Sensor Models

MeasurementModel — Measurement model for sensor

sensor measurement model object

Measurement model for the sensor, specified as a sensor measurement model object. You can use the sensorMeasurementModel function to generate the object. The model defines what the sensor measures and how it relates to the state of the target.

DetectabilityModel — Detectability model for sensor

sensor detectability model object

Detectability model for the sensor, specified as a sensor detectability model object. You can use the sensorDetectabilityModel function to generate the object. The model defines the sensor's fields of view and the probability of detecting a target at a given state within each field of view.

ClutterModel — Clutter model for sensor

sensor clutter model object

Clutter model for the sensor, specified as a sensor clutter model object. You can use the sensorClutterModel function to generate the object. The model defines the distribution of clutter in the measurement space.

BirthModel — Birth model for sensor

sensor birth model object

Birth model for the sensor, specified as a sensor birth model object. You can use the sensorBirthModel function to generate the object. The model defines the distribution of newly appearing targets in the measurement space.

General Properties

MaxNumMeasurements — Maximum number of measurements per update

32 (default) | positive integer

Maximum number of measurements per update, specified as a positive integer.

Example: 5

Data Types: single | double

UpdateModels — Option to enable updating sensor models with time and/or measurements

false (default) | true

Option to enable updating sensor models with time and measurements, specified as true or false. When you set this property to true, you can use the ModelUpdateFcn property to update the specification.

Example: true

Data Types: logical

MaxNumTimestamps — Maximum number of timestamps per update

32 (default) | positive integer

Maximum number of timestamps per update, specified as a positive integer. This property allows you to send time-varying data from the sensor to update the models.

To enable this property, set the UpdateModels property to true.

Example: 64

Data Types: single | double

ModelUpdateFcn — Model update function

function handle

Model update function, specified as a function handle. This property defines how to update the specification based on time and measurement. The function signature is spec = ModelUpdateFcn(spec,data).

data is a subset of the input data. You provide this subset as an input to the tracker. The tracker selects appropriate timestamps and measurements from the data and calls the function. Use the dataFormat function of the specification to understand the data format required by the sensor.

To enable this property, set the UpdateModels property to true.

Object Functions

dataFormat

Structure for data format required by task-oriented tracker

Examples

Create and Configure Specification for Marine Radar Using CustomSensor Specification

Create a specification for a marine radar. The radar of interest is on top of a stationary tower.

radarPosition = [0;0;35]; % radar's relative position to the tower origin.
towerPosition = [3800;15200;110]; % tower origin location in scenario coordinate.
radarOrientation = [0 1 0;-1 0 0;0 0 1]; % radar's relative orientation to the tower origin.
towerOrientation = [-0.2 0.6 0.7;0.9 0.3 0;-0.2 0.7 -0.6]; % tower orientation in scenario coordinate.
marineRadarSpec = trackerSensorSpec("custom")

marineRadarSpec = 
  CustomSensor with properties:

    MaxNumMeasurements: 32

      MeasurementModel: []
    DetectabilityModel: []
          ClutterModel: []
            BirthModel: []

          UpdateModels: 0

Define the measurement, detectability, clutter, and birth model of the marine radar specification. For measurement, specify that the radar of interest reports the position in the scenario coordinates.

measurementModel = sensorMeasurementModel("position");
measurementModel.OriginPosition = zeros(3,1);
measurementModel.Orientation = eye(3);

For detectability, specify that the radar detects targets within its field of view around a center beam.

detectabilityModel = sensorDetectabilityModel("field-of-view");
detectabilityModel.AzimuthLimits = [-10 10];
detectabilityModel.ElevationLimits = [-15 15];
detectabilityModel.RangeLimits = [0 10000];
detectabilityModel.OriginPosition = cat(2,radarPosition,towerPosition);
detectabilityModel.Orientation = cat(3,radarOrientation,towerOrientation);
detectabilityModel.DetectionProbability = 0.95;

For clutter, specify that the radar assumes a uniform Poisson clutter model, which assumes false measurements or noise (referred to as "clutter") in radar data are uniformly distributed across the observation space.

clutterModel = sensorClutterModel("uniform-poisson");
clutterModel.ClutterDensity = 5e-9;

For birth, specify that the radar assumes a uniform Poisson birth model, which assumes new targets can appear uniformly across the entire observation space.

birthModel = sensorBirthModel("uniform-poisson");
birthModel.BirthDensity = 5e-9;

Configure the marine radar specification using these models.

marineRadarSpec.MeasurementModel = measurementModel;
marineRadarSpec.DetectabilityModel = detectabilityModel;
marineRadarSpec.ClutterModel = clutterModel;
marineRadarSpec.BirthModel = birthModel;

To update the specification based on time or measurement, you can set the UpdateModels property to true and specify the ModelUpdateFcn function handle of the specification. For example, the following model update function allows you to update the radar center beam orientation with time, and update the position variance with measurement.

marineRadarSpec.UpdateModels = true;
marineRadarSpec.ModelUpdateFcn = @updateRadarSpec;
function spec = updateRadarSpec(spec, data)
if ~isempty(data.Time)
    spec.DetectabilityModel.Orientation(:,:,1) = data.TimeVaryingModelData.BeamOrientation;
end
if ~isempty(data.MeasurementTime)
    spec.MeasurementModel.PositionVariance = data.MeasurementVaryingModelData.PositionVariance;
end
end

More About

Data Format Required by Task-Oriented Tracker

When you initialize a tracker using this object, you need sensor data to update the tracker. For a full list of required sensor data and their descriptions, see the table below. See the dataFormat function for details on updating the tracker with sensor data.

Field Name	Description	Comment
MeasurementTime	A scalar or a 1-by-N array defining the timestamps of the measurements. N is the maximum number of measurements.	None
Measurements	An array representing measurements reported by the sensor concatenated along the columns.	None
Time	A 1-by-P array defining the timestamps of data reported by the sensor. P is the maximum number of timestamps.	Applies only when the UpdateModels property is set to true.
TimeVaryingModelData	A 1-by-P structure array defining the model data that changes with time. P is the maximum number of timestamps.	Applies only when the UpdateModels property is set to true.
MeasurementVaryingModelData	A 1-by-N structure array defining the model data that changes with measurements. N is the maximum number of measurements.	Applies only when the UpdateModels property is set to true.

Tip

To update the tracker at a timestamp when the sensor scan is not complete, specify "LookTime" as empty using zeros(0,1,dataType).

Version History

Introduced in R2025a