error_model¶
- error_model … end_error_model¶
error_model <derived-name> <base-name> ... Input for the error model ... end_error_model
Overview¶
error_model can be used to create configured error models that can be referenced in the definition of a Predefined Sensor Types. <derived-name> is the name by which the user wishes to refer to the configured error model. *<base-name>* is one of the Available Error Models:
Effective Use Of Error Models¶
An error model definition may be embedded directly in the definition of a radar. For example, assume you have a file called ‘ex_radar.txt’:
sensor EX_RADAR WSF_RADAR_SENSOR
transmitter
... transmitter commands ...
end_transmitter
receiver
... receiver commands ...
end_receiver
error_model <base-name>
... error model commands ...
end_error_model
end_sensor
The problem with this method is that one must modify the radar definition to change or eliminate the error model. In many production uses this is undesirable or infeasible. What would be more desirable is to provide a ‘default’ error model definition that can be overridden.
The new ‘ex_radar.txt’ would now contain:
# Define the 'default' error model
error_model EX_RADAR_ERROR <base-name>
... error model commands ...
end_error_model
sensor EX_RADAR WSF_RADAR_SENSOR
transmitter
... transmitter commands ...
end_transmitter
receiver
... receiver commands ...
end_receiver
error_model EX_RADAR_ERROR # References the error model symbolically
end_sensor
Then to override the error model:
#include ex_radar.txt
# Provide a new definition that overrides the existing definition.
# This example disables error calculations.
error_model EX_RADAR_ERROR none
end_error_model
The radar model will use the last definition of EX_RADAR_ERROR when it finally creates instances of the radar in the simulation.
Available Error Models¶
none¶
A ‘dummy’ error model that is the equivalent of no error.
error_model <derived-name> none
end_error_model
standard_sensor_error¶
A ‘standard’ error model that uses the azimuth_error_sigma, elevation_error_sigma, range_error_sigma and range_rate_error_sigma to calculate the error values.
error_model <derived-name> standard_sensor_error
end_error_model
radar_sensor_error¶
A ‘radar sensor’ error model that uses the beam errors specified by the receiver/transmitter data, e.g. beamwidths and bandwidths or the error_model_parameters block overrides.
Warning
Sensor type must be a WSF_RADAR_SENSOR.
error_model <derived-name> radar_sensor_error
end_error_model
absolute_sensor_error¶
An ‘absolute’ error model that defines a one standard deviation absolute position error measurement in two or three dimensions about the sensor detection target.
error_model <derived-name> absolute_sensor_error
end_error_model
- 2d_position_error_sigma <length-value>¶
Specify a one standard deviation position error to be applied to the track location in North and East directions about the sensor detection target. Applying this error will result in 68% of track position measurements being within a circle of radius <length-value> centered on the target’s truth position. Target altitude will be reported without error.
- 3d_position_error_sigma <length-value>¶
Specify a one standard deviation position error to the track in the NED (North, East, and Down) directions about the sensor detection target. Applying this error will result in 68% of track position measurements being within a sphere of radius <length-value> centered on the target’s truth position.
bistatic_error¶
This error model still uses the sensor mode’s azimuth_error_sigma and elevation_error_sigma. Its function is to use the instantaneous measurement to calculated the dynamic range sigma. This command is mutually exclusive with range_sigma, transmit_only, and compute_measurement_errors. The latter command would cause this model to be bypassed. This model requires a direct line of sight to both the transmitter (direct signal) and to the target (reflected signal) to get a successful detection.
The error model is based on paper “A Three-dimensional Bistatic Radar Target Position Measurement Error Model”, R. K. Lynn.
error_model <derived-name> bistatic_error realistic_blurring time_reflected_sigma ... time_direct_sigma ... transmitter_position_sigmas ... end_transmitter_position_sigmas end_error_model
- realistic_blurring¶
Specifies to apply a Gaussian distrubution to the range error based on the calculated dynamic range error sigma.
Default: disabled
- time_reflected_sigma <time-value>¶
Specifies the reflected time measurement sigma. The reflected time, or scatter time (ts), is the time of reception of a signal that travels from transmitter to target and then to receiver.
- time_direct_sigma <time-value>¶
Specifies the direct time measurement sigma. The direct time (tx) is the time of reception of a signal that travels from transmitter directly to the receiver.
- transmitter_position_sigmas <length-value> … end_transmitter_position_sigmas¶
Specifies a dual-key table of transmitter platform to the sigmas associated with their location measurement sigmas. Note that the transmitter in a bistatic transaction can be on the red/opposite team. The key is a pairing of the side and domain.
The format of the table is:
transmitter_position_sigmas <length-value> # side domain position_sigma_x position_sigma_y position_sigma_z * blue land 10 10 10* * blue air 20 20 20* * red land 5000 5000 5000* * red air 5000 5000 5000* end_transmitter_position_sigmas
trimsim_error¶
See also
WSF_TRIMSIM_PROCESSOR to fully implement and apply this error model’s errors.
This error model is a required companion to WSF_TRIMSIM_PROCESSOR to provide the parameters for error calculations. The commands for this error model define the various sources of error used in the TDOA algorithm. Establish TDOA parameters for master and slave TDOA ESM sensors, if applicable.
Note
Sensor mode errors are ignored when these are defined.
error_model <derived-name> trimsim_error north_position_error_sigma ... east_position_error_sigma ... down_position_error_sigma ... reference_time_error ... inter_system_time_delay ... sensor_timing_error ... atmospheric_refraction_residual ... ground_target_altitude_error ... end_error_model
- north_position_error_sigma <length-value>¶
Defines the sensing platform’s north target location error.
Default: 0 m
- east_position_error_sigma <length-value>¶
Defines the sensing platform’s east target location error.
Default: 0 m
- down_position_error_sigma <length-value>¶
Defines the sensing platform’s down target location errors.
Default: 0 m
- reference_time_error <time-value>¶
Needs description.
Default: 0 sec
- inter_system_time_delay <time-value>¶
Defines the relative timing error between the targeting sensor and the reference system (e.g., INS/GPS).
Default: 0 sec
- sensor_timing_error <time-value>¶
Defines the targeting sensor’s internal time measurement error.
Default: 0 sec
- atmospheric_refraction_residual <unitless>¶
Defines the atmospheric refraction compensation error, residual part.
Default: 0.0
- ground_target_altitude_error <length-value>¶
Defines the altitude error to use for the special case of 3 platforms detecting a “land” or “surface” target. The algorithm still requires a master node and at least 3 slave nodes detecting the target for all other types of targets (e.g., air, unknown) or if this value is not defined.
