Simulation Accelerometer 1 Bias (SIM_ACC1_BIAS)

Description

SIM_ACC1_BIAS allows you to test how ArduPilot handles a "Drifty" sensor.

Real accelerometers always have a slight offset (e.g. they might report 0.1 $m/s^2$ even when sitting perfectly level). ArduPilot calibrates this out during the "Accel Cal" process. By setting this parameter in SITL, you can intentionally introduce an error to verify that your calibration process or the EKF can handle it.

Tuning & Behavior

• Default Value: 0.
• Testing: Set to 0.5. If you haven't performed an Accel Cal in the simulation, the drone will think it is tilted and try to roll away.

Simulated Accelerometer 1 Noise (SIM_ACC1_RND)

Description

SIM_ACC1_RND allows you to test the robustness of the autopilot's navigation filters (EKF) by injecting artificial noise into the first simulated accelerometer.

In a real drone, motors and propellers create significant vibration. By increasing this parameter in SITL, you can see how much "shaking" your drone can tolerate before it loses its position estimate or becomes unstable.

The Engineer's View

Defined in SITL.cpp.
The simulation physics engine calculates the "True" acceleration of the vehicle. This parameter sets the standard deviation ($\sigma$) of a Gaussian distribution that is added to each sample:
$$ Accel\_{read} = Accel\_{true} + \mathcal{N}(0, \text{SIM\_ACC1\_RND}) $$

Tuning & Behavior

• Default Value: 0 (Perfect, noise-free sensor).
• Recommendation: Set to 0.5 or 1.0 to simulate a typical frame with some vibration. Set to 5.0+ to simulate a "Worst-case" high-vibration scenario.

Simulation Accelerometer 1 Scale (SIM_ACC1_SCAL)

Description

SIM_ACC1_SCAL simulates a "Sensitivity Error."

If an accelerometer is perfectly calibrated, it should report exactly 9.81 $m/s^2$ when facing down. A scale error means it might report 9.90 or 9.70 instead.

• 0 (Default): Perfect scale.
• 0.05: 5% scale error.

Tuning & Behavior

• Default Value: 0.
• Testing: Use to verify the effectiveness of the 6-point Accel Calibration routine.

Simulation Accelerometer 2 Bias (SIM_ACC2_BIAS)

Description

SIM_ACC2_BIAS simulates drift on the secondary accelerometer.

See SIM_ACC1_BIAS for details.

Accel 2 motor noise factor

Note: This parameter functions identically to SIM_ACC1_RND.

Simulation Accelerometer 2 Scale (SIM_ACC2_SCAL)

Description

SIM_ACC2_SCAL simulates sensitivity errors on the secondary accelerometer.

See SIM_ACC1_SCAL for details.

Simulation Accelerometer 3 Bias (SIM_ACC3_BIAS)

Description

SIM_ACC3_BIAS simulates drift on the tertiary IMU.

See SIM_ACC1_BIAS for details.

Accel 3 motor noise factor

Note: This parameter functions identically to SIM_ACC1_RND.

Accel 3 scaling factor

Note: This parameter configures instance 3. It functions identically to SIM_ACC1_SCAL.

Accel 4 bias

Note: This parameter configures instance 4. It functions identically to SIM_ACC1_BIAS.

Accel 4 motor noise factor

Note: This parameter functions identically to SIM_ACC1_RND.

Accel 4 scaling factor

Note: This parameter configures instance 4. It functions identically to SIM_ACC1_SCAL.

Accel 5 bias

Note: This parameter configures instance 5. It functions identically to SIM_ACC1_BIAS.

Accel 5 motor noise factor

Note: This parameter functions identically to SIM_ACC1_RND.

Accel 4 scaling factor

Note: This parameter configures instance 5. It functions identically to SIM_ACC1_SCAL.

Simulated Accelerometer 1 Failure (SIM_ACCEL1_FAIL)

Description

SIM_ACCEL1_FAIL allows you to simulate a catastrophic hardware failure of your primary accelerometer.

When set to 1, the sensor stops providing data. This is used by developers to verify that the "Lane Switching" logic in EKF3 correctly identifies the dead sensor and automatically switches the drone's control to Accelerometer 2 or 3 without crashing.

The Engineer's View

When this flag is set, the SITL backend for the IMU returns false on its read() calls or provides static/zero data. This triggers the EKF health monitoring system to mark the lane as unhealthy.

Tuning & Behavior

• Default Value: 0 (Sensor working normally).
• Recommendation: Only set to 1 while in flight in a safe simulation to verify your drone's redundant systems are working as expected.

ACCEL2 Failure

Note: This parameter functions identically to SIM_ACCEL1_FAIL.

ACCEL3 Failure

Note: This parameter functions identically to SIM_ACCEL1_FAIL.

ACCEL4 Failure

Note: This parameter functions identically to SIM_ACCEL1_FAIL.

ACCEL5 Failure

Note: This parameter functions identically to SIM_ACCEL1_FAIL.

Simulated Accelerometer Failure Mask (SIM_ACC_FAIL_MSK)

Description

SIM_ACC_FAIL_MSK allows you to "kill" specific accelerometers in the simulator.

ArduPilot typically runs 3 IMUs (Inertial Measurement Units). By disabling one or two, you can verify that the EKF (Extended Kalman Filter) correctly switches to the remaining healthy sensors.

• Bit 0 (1): Fail Accel 1
• Bit 1 (2): Fail Accel 2
• Bit 2 (4): Fail Accel 3

Tuning & Behavior

• Default Value: 0 (All sensors active).
• Testing: Set to 1 to kill Accel 1. Watch the EKF3.Lane messages in the GCS console to see the switch occur.

Simulated Accelerometer File Read/Write (SIM_ACC_FILE_RW)

Description

SIM_ACC_FILE_RW allows you to "record" the vibration and movement of a real flight and "replay" it in the simulator.

This is an incredibly powerful tool for tuning filters. You can fly your real drone, capture the raw accelerometer noise, and then feed that exact noise into the simulator to test if your notch filters or EKF settings can handle it.

• 0: Disabled (Standard simulation).
• 1: Read data from file (Replay).
• 2: Write data to file (Record).

Tuning & Behavior

• Default Value: 0.
• Recommendation: Use 2 during a short hover to capture a noise profile, then 1 to replay it while tuning INS_HNTCH_FREQ.

Simulation Accelerometer Trim (SIM_ACC_TRIM)

Description

SIM_ACC_TRIM simulates a drone where the flight controller isn't mounted perfectly level.

It injects a constant tilt into the accelerometer data. This is used to test how robust the EKF and flight controllers are to slight misalignments and to verify that "Accel Calibration" or "AHRS Trim" procedures work correctly in SITL.

Simulated ADSB Altitude (SIM_ADSB_ALT)

Description

SIM_ADSB_ALT sets the cruising altitude for the fake traffic generated by SIM_ADSB_COUNT.

Tuning & Behavior

• Default Value: 1000 m.
• Testing: Set this to your flying altitude (e.g., 50m) to force "Near Miss" events.

Simulated ADSB Aircraft Count (SIM_ADSB_COUNT)

Description

SIM_ADSB_COUNT populates the sky with fake airplanes.

This allows you to test the "ADSB Avoidance" logic (AVOID_ADSB) without needing a real ADSB receiver or real planes flying nearby.

• -1: Disabled.
• 0: Enabled but 0 planes.
• 1+: Generates X random aircraft flying near your home location.

Tuning & Behavior

• Default Value: -1 (Disabled).
• Testing: Set to 5 to see random traffic on your GCS map. Fly towards them to verify your drone triggers a failsafe or avoidance maneuver.

Simulated ADSB Radius (SIM_ADSB_RADIUS)

Description

SIM_ADSB_RADIUS sets the size of the "arena" for the simulated air traffic.

Simulated planes will spawn and fly within this distance from your home point.

Tuning & Behavior

• Default Value: 10000 m (10 km).
• Recommendation: Lower this to 1000 or 2000 if you want the traffic to be denser and closer to your drone for easier testing.

Simulated ADSB Transmission (SIM_ADSB_TX)

Description

SIM_ADSB_TX simulates the presence of an ADSB "Out" unit on your drone.

When enabled, the simulator will act as if it is broadcasting your position to the world. This is primarily for checking that the ADSB_RF_SELECT and other transponder settings are configured correctly in the GCS.

Tuning & Behavior

• Default Value: 0 (Disabled).
• 1: Enabled.

Simulated ADSB Emitter Types (SIM_ADSB_TYPES)

Description

SIM_ADSB_TYPES filters the kind of "Fake Planes" the simulator generates.

If you only want to test how your drone reacts to other drones (UAVs), you can disable the "747 Jumbo Jet" simulation.

• Bit 0: Light (Cessna)
• Bit 1: Small (Learjet)
• Bit 2: Large (747)
• Bit 14: UAV

Tuning & Behavior

• Default Value: 0 (All types).
• Recommendation: Leave at 0 to test against a realistic mix of air traffic.

Simulation AIS Radius (SIM_AIS_RADIUS)

Description

SIM_AIS_RADIUS enables the simulation of other ships for maritime operations.

When set to a positive value, ArduPilot will generate "Fake" ships (AIS targets) within this distance. This allows you to test obstacle avoidance and traffic monitoring systems on boats and autonomous ships.

Airspeed sensor failure

Note: This parameter functions identically to SIM_ARSPD_FAIL.

Airspeed sensor failure pressure

Note: This parameter functions identically to SIM_ARSPD_FAILP.

Compass offsets in milligauss on the Z axis

Note: This parameter functions identically to SIM_ARSPD_OFS.

Airspeed pitot tube failure pressure

Note: This parameter functions identically to SIM_ARSPD_PITOT.

Airspeed ratio

Note: This parameter functions identically to SIM_ARSPD_RATIO.

None

Note: This parameter functions identically to SIM_ARSPD_RND.

Airspeed signflip

Note: This parameter functions identically to SIM_ARSPD_SIGN.

Simulated Airspeed Failure Value (SIM_ARSPD_FAIL)

Description

SIM_ARSPD_FAIL allows you to simulate a "Stuck Sensor" or a "Clogged Pitot Tube."

By setting this to a static value (like 0 or 100), you can verify that the autopilot detects the failure and switches to "Synthetic Airspeed" (estimating speed from throttle and pitch) or triggers a failsafe.

The Engineer's View

If this value is non-zero (or if you toggle the failure flag in the SITL backend), the sensor driver will lock its output to this value.

• 0 m/s: Simulates a pitot tube cover left on.
• High Value: Simulates a sensor blowing out or water ingress.

Tuning & Behavior

• Default Value: 0 (Disabled/Normal Operation).
• Testing: Set to 0 while flying to simulate a blockage. Watch if the EKF declares the sensor "Unhealthy."

Simulated Airspeed Failure Pressure (SIM_ARSPD_FAILP)

Description

SIM_ARSPD_FAILP allows you to choose what "Broken" looks like for your Pitot tube.

If SIM_ARSPD_FAIL is active, the sensor will freeze at this pressure.

• 0 Pa: Simulates a clogged tube (Zero airspeed). Useful for testing stall warnings.
• High Value: Simulates a blocked static port (High airspeed).

Tuning & Behavior

• Default Value: 0 Pa.

Simulated Airspeed Offset (SIM_ARSPD_OFS)

Description

SIM_ARSPD_OFS simulates a calibration error.

Airspeed sensors measure minute pressure differences. If the sensor isn't zeroed correctly before flight (e.g., if it was windy when you plugged in the battery), it will report speed even when sitting still. This parameter allows you to simulate that error and test if your pre-flight checks catch it.

Tuning & Behavior

• Default Value: 0 Pa.
• Testing: Set to 100. You should see the HUD report an airspeed of 5-10 m/s even while the drone is on the ground.

Simulated Pitot Blockage Pressure (SIM_ARSPD_PITOT)

Description

SIM_ARSPD_PITOT simulates a blocked pitot tube (e.g., mud wasp nest).

If you set SIM_ARSPD_FAIL to enable failure, this is the pressure value the sensor will output.

Tuning & Behavior

• Default Value: 0 Pa.

Simulated Airspeed Ratio (SIM_ARSPD_RATIO)

Description

SIM_ARSPD_RATIO sets the sensitivity of the virtual pitot tube.

This corresponds to the ARSPD_RATIO parameter in the flight controller. If they don't match, your airspeed reading will be wrong.

Tuning & Behavior

• Default Value: 2.
• Testing: Change this to 3 and see if ARSPD_AUTOCAL can figure it out.

Simulated Airspeed Noise (SIM_ARSPD_RND)

Description

SIM_ARSPD_RND injects noise into the virtual pitot tube.

Airspeed sensors are notoriously noisy due to wind gusts and turbulence. This parameter helps you tune your TECS (Total Energy Control System) to ignore that noise.

• 0: Perfect, clean airspeed data.
• 2 (Default): Realistic turbulence.

Tuning & Behavior

• Default Value: 2.0 m/s.
• Recommendation: Keep at 2.0 to ensure your PID tuning is robust enough for real-world flight.

Simulated Airspeed Sign (SIM_ARSPD_SIGN)

Description

SIM_ARSPD_SIGN simulates a common plumbing error: swapping the Pitot and Static tubes.

If set to -1, the airspeed sensor will report negative pressure, which typically results in zero airspeed or an error message.

Tuning & Behavior

• Default Value: 1.

Pivot Delay

Note: This parameter functions identically to SIM_BARO_DELAY.

Barometer disable

Note: This parameter functions identically to SIM_BARO_DISABLE.

Barometer altitude drift

Note: This parameter functions identically to SIM_BARO_DRIFT.

Barometer freeze

Note: This parameter functions identically to SIM_BARO_FREEZE.

Barometer glitch

Note: This parameter functions identically to SIM_BARO_GLITCH.

None

Note: This parameter functions identically to SIM_BARO_RND.

Wind coefficient backward

Note: This parameter functions identically to SIM_BARO_WCF_BAK.

Pressure error coefficient in negative Z direction (down)

Note: This parameter functions identically to SIM_BARO_WCF_DN.

Pressure error coefficient in positive X direction (forward)

Note: This parameter functions identically to SIM_BARO_WCF_FWD.

Pressure error coefficient in negative Y direction (left)

Note: This parameter functions identically to SIM_BARO_WCF_LFT.

Pressure error coefficient in positive Y direction (right)

Note: This parameter functions identically to SIM_BARO_WCF_RGT.

Pressure error coefficient in positive Z direction (up)

Note: This parameter functions identically to SIM_BARO_WCF_UP.

Pivot Delay

Note: This parameter functions identically to SIM_BARO_DELAY.

Barometer disable

Note: This parameter functions identically to SIM_BARO_DISABLE.

Barometer altitude drift

Note: This parameter functions identically to SIM_BARO_DRIFT.

Barometer freeze

Note: This parameter functions identically to SIM_BARO_FREEZE.

Barometer glitch

Note: This parameter functions identically to SIM_BARO_GLITCH.

None

Note: This parameter functions identically to SIM_BARO_RND.

Wind coefficient backward

Note: This parameter functions identically to SIM_BARO_WCF_BAK.

Pressure error coefficient in negative Z direction (down)

Note: This parameter functions identically to SIM_BARO_WCF_DN.

Pressure error coefficient in positive X direction (forward)

Note: This parameter functions identically to SIM_BARO_WCF_FWD.

Pressure error coefficient in negative Y direction (left)

Note: This parameter functions identically to SIM_BARO_WCF_LFT.

Pressure error coefficient in positive Y direction (right)

Note: This parameter functions identically to SIM_BARO_WCF_RGT.

Pressure error coefficient in positive Z direction (up)

Note: This parameter functions identically to SIM_BARO_WCF_UP.

Simulated Barometer Count (SIM_BARO_COUNT)

Description

SIM_BARO_COUNT defines how many virtual atmospheric pressure sensors are available to the autopilot.

By increasing this to 2 or 3, you can test ArduPilot's multi-baro redundancy and health monitoring. You can then use other SIM_BARx_... parameters to fail one sensor and watch the EKF switch to the backup.

Tuning & Behavior

• Default Value: 1.
• Recommendation: Set to 2 for a realistic simulation of standard flight controller hardware (which often has two baros).
• Reboot Required: Yes.

Simulated Barometer Delay (SIM_BARO_DELAY)

Description

SIM_BARO_DELAY adds lag to the altitude reading. High lag can cause the drone to "bounce" in AltHold because the controller is reacting to where the drone was, not where it is.

Tuning & Behavior

• Default Value: 0
• Recommendation: Use to test controller stability.

Disable Simulated Barometer (SIM_BARO_DISABLE)

Description

SIM_BARO_DISABLE kills the primary barometer signal.

Use this to test your drone's ability to maintain altitude using ONLY the IMU (which will drift) or a secondary source (like a Rangefinder).

Tuning & Behavior

• Default Value: 0
• Recommendation: Use in flight to verify your "Secondary Altitude Source" logic.

Simulated Barometer Drift (SIM_BARO_DRIFT)

Description

SIM_BARO_DRIFT simulates a barometer that is slowly losing calibration or being affected by changing weather pressure.

Real barometers drift as the weather changes (e.g., a storm front moving in). This parameter adds a constant vertical velocity error to the sensor.

Tuning & Behavior

• Default Value: 0 m/s.
• Recommendation: Set to 0.1 m/s to test if the EKF can use GPS vertical velocity to correct the baro drift.

Simulated Barometer Freeze (SIM_BARO_FREEZE)

Description

SIM_BARO_FREEZE locks the barometer value.

This simulates a sensor driver crash or a clogged static port. If the drone climbs or descends, the barometer will report 0 vertical speed.

Tuning & Behavior

• Default Value: 0 (Disabled).
• 1: Freeze enabled.

Simulated Barometer Glitch (SIM_BARO_GLITCH)

Description

SIM_BARO_GLITCH applies an instant step-change to the altitude reading.

This simulates events like opening a window in a pressurized room or a sudden pressure wave from a passing truck.

Tuning & Behavior

• Default Value: 0 m.
• Testing: Set to 50 (meters) while hovering. Verify that the drone does NOT shoot up/down 50 meters instantly. The EKF should reject the jump or smooth it out.

Simulated Barometer Noise (SIM_BARO_RND)

Description

SIM_BARO_RND simulates atmospheric pressure noise. Since ArduPilot uses the barometer for altitude, this noise directly affects how "bouncy" the altitude hold is in flight.

The Engineer's View

Adds Gaussian noise to the simulated pressure reading. Because 1 Pascal is roughly 8cm of altitude at sea level, a noise value of 0.2 represents about 1.6cm of altitude jitter.

Tuning & Behavior

• Default Value: 0.2 Pa
• Effect of Increasing: The drone will struggle to maintain a precise altitude, and the climb rate estimate will become noisier.

Simulation Barometer Wind Coefficient Backward (SIM_BARO_WCF_BAK)

Description

SIM_BARO_WCF_BAK simulates pressure errors when the drone is flying backwards.

See SIM_BARO_WCF_FWD for more details.

Simulation Baro Wind Coeff (SIM_BARO_WCF_DN)

Description

SIM_BARO_WCF_DN simulates aerodynamic interference that makes the altitude reading glitch during a fast descent.

See BARO1_WCF_ENABLE for details on the real-world compensation model. This parameter allows you to inject those same errors into SITL to test your compensation tuning.

Simulation Barometer Wind Coefficient Forward (SIM_BARO_WCF_FWD)

Description

SIM_BARO_WCF_FWD simulates "Static Port Error."

On real planes, as the airspeed increases, the pressure around the fuselage drops (Bernoulli's principle). If your barometer isn't perfectly vented, this can cause the drone to think it is climbing when it is actually just speeding up. This parameter allows you to simulate that effect to test compensation algorithms (BARO_WCF_ENABLE).

The Mathematics

The pressure error ($\Delta P$) is calculated as:
$$ \Delta P = \text{WCF} \cdot \frac{1}{2} \cdot \rho \cdot V^2 $$

Where:

• $V$ is airspeed in the forward direction.
• $\rho$ is air density.

Tuning & Behavior

• Default Value: 0.
• Testing: Set to 0.02. Fly the drone fast in a straight line. If you see the reported altitude change while you are at a constant height, the simulation is working.

Simulated Baro Wind Comp Factor Left (SIM_BARO_WCF_LFT)

Description

Defines pressure change due to wind from the left. See SIM_BARO_WCF_UP.

Simulated Baro Wind Comp Factor Right (SIM_BARO_WCF_RGT)

Description

Defines pressure change due to wind from the right. See SIM_BARO_WCF_UP.

Simulated Baro Wind Comp Factor Up (SIM_BARO_WCF_UP)

Description

SIM_BARO_WCF_UP simulates the "Bernoulli Effect" on your static port.

When wind blows across a hole (static port), it creates a pressure drop (or rise), causing the drone to think it is at a different altitude. This parameter defines how much the reported pressure changes when wind hits the drone from the top.

The Mathematics

$$ \Delta P = C\_{up} \times V\_{up}^2 $$

Tuning & Behavior

• Default Value: 0.
• Recommendation: Use -0.05 to simulate a typical drone where propwash creates a low-pressure zone above the flight controller.

Simulation Battery Capacity (SIM_BATT_CAPACITY)

Description

SIM_BATT_CAPACITY defines the size of the virtual fuel tank.

SITL calculates current draw based on motor thrust. This parameter allows you to test battery failsafe logic by simulating a realistic discharge curve.

Tuning & Behavior

• Default Value: 10000 mAh.
• Testing: Set to a small value (e.g. 500) to quickly trigger a "Low Battery" failsafe during a test flight.

Simulated Battery Capacity (SIM_BATT_CAP_AH)

Description

SIM_BATT_CAP_AH defines how much "Fuel" the virtual battery has.

As you fly in SITL, the autopilot calculates current draw based on motor throttle. This parameter determines how fast the voltage drops. If set to 0, the battery is "Infinite" and will never drain.

Simulation Battery Voltage (SIM_BATT_VOLTAGE)

Description

SIM_BATT_VOLTAGE sets the initial charge state.

Tuning & Behavior

• Default Value: 12.6 V (3S Lipo).
• Testing: Set to 10.5 to test Battery Failsafe trigger on boot or takeoff.

Simulated Baud Rate Limiting Enable (SIM_BAUDLIMIT_EN)

Description

SIM_BAUDLIMIT_EN forces the simulator to respect the physics of serial data transfer speeds.

By default, SITL sends data as fast as the CPU allows. If you enable this, a simulated 57600 baud link will actually choke if you try to send too much data, causing packet loss and latency.

Tuning & Behavior

• Default Value: 0 (Unlimited speed).
• Recommendation: Enable this when testing telemetry radios or low-bandwidth links to verify your stream rates (SRx_params) are configured correctly.

Simulation Buoyancy (SIM_BUOYANCY)

Description

SIM_BUOYANCY defines how much the simulated submarine wants to float or sink.

• Positive Value: Net upwards force (Positive buoyancy). The sub floats to the surface.
• Negative Value: Net downwards force (Negative buoyancy). The sub sinks to the bottom.
• 0: Neutral buoyancy. The sub stays at its current depth (Ideal for ROVs).

Tuning & Behavior

• Testing: Essential for tuning the vertical depth controller on ArduSub.

Simulation Buzzer Enable (SIM_BZ_ENABLE)

Description

SIM_BZ_ENABLE activates a virtual beeper.

When enabled, SITL will log and potentially play sound for arming beeps, failsafe warnings, and other audio cues produced by the autopilot. Useful for debugging new melody patterns or verifying failsafe alerts.

Simulation Buzzer Pin (SIM_BZ_PIN)

Description

SIM_BZ_PIN tells the simulator which virtual pin is connected to the beeper.

Simulated CAN Servo Mask (SIM_CAN_SRV_MSK)

Description

SIM_CAN_SRV_MSK tells the simulator which motors or servos are "Digital" (CAN).

Normally, SITL simulates servos as direct wires. If you are developing or testing DroneCAN hardware (using AP_Periph), you can set this mask. Any bit set to 1 will cause the simulator to expect that channel's data to come from a virtual CAN node rather than the main flight controller's internal logic.

Tuning & Behavior

• 0: All servos simulated as direct internal connections.
• Bit 0 (1): Servo 1 is a CAN servo.
• Bit 3 (8): Servo 4 is a CAN servo.

Simulated CAN 1 Transport Type (SIM_CAN_TYPE1)

Description

SIM_CAN_TYPE1 tells the simulator how to send "CAN Messages" between SITL and other simulated devices (like a DroneCAN GPS).

• 0: None.
• 1: MulticastUDP (Default). Sends messages over your computer's local network. This is the standard way SITL talks to the "CANDevices" or "UAVCAN GUI Tool."
• 2: SocketCAN. Uses the Linux kernel's native CAN bus driver (Linux only).

Tuning & Behavior

• Default Value: 1.
• Recommendation: Leave at 1 for all standard DroneCAN testing.

transport type for second CAN interface

Note: This parameter functions identically to SIM_CAN_TYPE1.

Simulated Clamp Channel (SIM_CLAMP_CH)

Description

SIM_CLAMP_CH creates a virtual "Mag-Lock" on the landing gear.

When the selected RC channel is High (PWM > 1800), the drone is physically stuck to the ground, regardless of throttle. This is useful for testing "Ground Idle" vibration or tuning PID loops without the drone taking off.

Tuning & Behavior

• 0: Disabled.
• 1-16: RC Channel number.

Simulation GPS Drift Speed (SIM_DRIFT_SPEED)

Description

SIM_DRIFT_SPEED simulates the "Wandering" effect of GPS.

Real GPS position is never perfectly still; it slowly drifts around a central point due to atmospheric changes. This parameter controls how fast that drift moves.

Tuning & Behavior

• Default Value: 0.05 m/s.
• Testing: Increase to 0.2 to test if your Loiter PID tuning is tight enough to hold position against a "moving" GPS target.

Simulation GPS Drift Time (SIM_DRIFT_TIME)

Description

SIM_DRIFT_TIME controls how often the GPS drift changes direction.

See SIM_DRIFT_SPEED.

Simulated EFI Type (SIM_EFI_TYPE)

Description

SIM_EFI_TYPE adds a virtual engine to the simulation.

• 0: Disabled.
• 1: MegaSquirt.
• 2: Loweheiser.
• 8: Hirth.

Tuning & Behavior

• Default Value: 0.
• Usage: Enable this to test your EFI_* parameter configuration and OSD layout.

Simulated Engine Failure (SIM_ENGINE_FAIL)

Description

SIM_ENGINE_FAIL selects the victim motor for failure testing.

• -1 (Default): No failure.
• 0: Motor 1 fails.
• 1: Motor 2 fails.

Tuning & Behavior

• Default Value: -1.
• Procedure:
  1. Take off and hover.
  2. Set SIM_ENGINE_MUL to 0.
  3. Set SIM_ENGINE_FAIL to 0 (Motor 1).
  4. Observe if the drone crashes or spins.

Simulation Engine Multiplier (SIM_ENGINE_MUL)

Description

SIM_ENGINE_MUL allows you to kill or weaken a motor in flight.

This is the primary tool for testing multirotor motor redundancy (e.g. Octocopter failure) or plane engine-out handling.

• 1.0 (Default): Full power.
• 0.0: Complete motor failure.
• 0.5: 50% power loss (damaged prop or ESC).

Tuning & Behavior

• Usage: You must also set SIM_ENGINE_FAIL to the motor number (0-indexed) you want to affect.

Simulated ESC Armed RPM (SIM_ESC_ARM_RPM)

Description

SIM_ESC_ARM_RPM sets the "Idle Speed" for the virtual RPM feedback.

Tuning & Behavior

• Default Value: 0.
• Recommendation: Set to 500 or 1000 to simulate the low-end spinning of motors while the drone is on the ground but armed.

Simulated ESC Telemetry Type (SIM_ESC_TELEM)

Description

SIM_ESC_TELEM enables the virtual return path for motor data.

If you are testing DShot ESC Telemetry or RPM filtering, you need this enabled so the autopilot "sees" the RPM and voltage data coming back from the virtual ESCs.

• 0: Disabled.
• 1: Enabled (Standard RPM + Voltage).
• 2: Bidirectional DShot (RPM only, but high-speed).

Tuning & Behavior

• Default Value: 0.
• Recommendation: Set to 1 to verify your OSD battery display and motor fail detection.

Simulated Floating Point Exceptions (SIM_FLOAT_EXCEPT)

Description

SIM_FLOAT_EXCEPT is a developer safety tool.

If enabled, the simulator will immediately "Hard Crash" if any part of the code performs an illegal math operation (like dividing by zero or taking the square root of a negative number). This is vital for catching bugs before they are ever flown on real hardware.

Tuning & Behavior

• Default Value: 1 (Enabled).
• Recommendation: Keep at 1 at all times unless you are debugging a known math issue that you need the simulator to bypass.

Simulated Optical Flow Delay (SIM_FLOW_DELAY)

Description

SIM_FLOW_DELAY simulates the processing lag of a smart camera (like HereFlow or PX4Flow).

Tuning & Behavior

• Default Value: 0 ms.
• Recommendation: Set to 20 to match real hardware.

Simulated Optical Flow Enable (SIM_FLOW_ENABLE)

Description

SIM_FLOW_ENABLE adds a virtual Optical Flow camera to the drone.

This allows you to test non-GPS loiter modes (FlowHold) and indoor navigation logic.

Tuning & Behavior

• Default Value: 0 (Disabled).
• 1: Enabled.

Simulation Optical Flow Position (SIM_FLOW_POS)

Description

SIM_FLOW_POS defines where the optical flow sensor is mounted in the simulator.

Just like the IMU and GPS, if the optical flow sensor is away from the COG, it will experience extra movement during rotations. This parameter tests the flight controller's ability to use the FLOW_POS_X/Y/Z parameters to compensate for these "lever arm" effects.

Simulated Optical Flow Rate (SIM_FLOW_RATE)

Description

SIM_FLOW_RATE sets the data frequency of the virtual flow sensor.

Tuning & Behavior

• Default Value: 10 Hz.
• Recommendation: Match your hardware specs (e.g., 50Hz for high-end sensors).

Simulated Optical Flow Noise (SIM_FLOW_RND)

Description

SIM_FLOW_RND simulates the "jitter" of an optical flow sensor looking at a difficult surface (like grass or carpet).

Tuning & Behavior

• Default Value: 0.05 $rad/s$.
• Recommendation: Increase to 0.2 to test if your drone can hold position over low-contrast surfaces.

Simulation FETtec OneWire ESC Enable (SIM_FTOWESC_ENA)

Description

SIM_FTOWESC_ENA activates the virtual FETtec OneWire interface.

This allows you to test the SERVO_FTW_MASK configuration and RPM telemetry feedback without having a physical FETtec ESC board connected.

Simulated TOWESC Power (SIM_FTOWESC_POW)

Description

SIM_FTOWESC_POW defines the maximum power capacity of the heavy-lift motor simulation.

Simulation Balloon Burst (SIM_GLD_BLN_BRST)

Description

SIM_GLD_BLN_BRST triggers the "Release" phase of a balloon glider test.

For drones that are carried to high altitudes by balloons, this parameter allows you to simulate the moment the balloon pops or the drone is released, instantly transitioning the physics model from buoyant ascent to aerodynamic glide.

Simulated Glider/Balloon Rate (SIM_GLD_BLN_RATE)

Description

SIM_GLD_BLN_RATE sets the physics resolution for slow-moving airframes like gliders and weather balloons.

Simulated Ground Behavior (SIM_GND_BEHAV)

Description

SIM_GND_BEHAV modifies how the drone interacts with the virtual earth.

• -1: Automatic (standard).
• 0: Non-Tailsitter (stays flat).
• 1: Tailsitter (leans back onto its tail).
• 2: Stay on ground (locked position).

Tuning & Behavior

• Default Value: -1.
• Recommendation: Leave at -1 unless you are testing a tailsitter QuadPlane.

Simulated GPS 1 Altitude Offset (SIM_GPS1_ALT_OFS)

Description

SIM_GPS1_ALT_OFS adds a constant error to the GPS altitude.

This is used to verify that the EKF can handle a disagreement between the Barometer (which reports correct altitude) and the GPS (which reports offset altitude).

Tuning & Behavior

• Default Value: 0 m.
• Testing: Set to 20. The EKF should initially report a large height innovation (error), then slowly shift the GPS bias or reject the GPS.

Simulated GPS 1 Enable (SIM_GPS1_ENABLE)

Description

SIM_GPS1_ENABLE is the power switch for the virtual GPS.

If you want to test how your drone flies with ONLY the secondary GPS, or no GPS at all, you can use this parameter to turn off the primary unit.

Tuning & Behavior

• Default Value: 1 (Enabled).
• 0: Disabled.

Simulated GPS 1 Heading Offset (SIM_GPS1_HDG_OFS)

Description

SIM_GPS1_HDG_OFS adds a constant error to the heading reported by the GPS.

This is only relevant if SIM_GPS_HDG is enabled (simulating a Dual Antenna GPS). It tests the EKF's ability to handle Compass/GPS yaw disagreement.

Tuning & Behavior

• Default Value: 0 deg.
• Testing: Set to 90. The EKF should trigger a "Yaw Alignment" error.

Simulated GPS 1 Type (SIM_GPS1_TYPE)

Description

SIM_GPS1_TYPE tells the simulator which GPS language to speak to the autopilot.

• 1: UBlox (Default). The standard binary protocol used by M8N/F9P modules.
• 5: NMEA. The standard text-based protocol used by older or generic GPS units.
• 19: MSP. MultiWii Serial Protocol, used by DJI or Walksnail video systems to pass GPS data.

Tuning & Behavior

• Default Value: 1.
• Recommendation: Keep at 1 (UBlox) for the most realistic simulation of standard ArduPilot hardware.

GPS 2 Accuracy

Note: This parameter functions identically to SIM_GPS_ACC.

Compass offsets in milligauss on the Z axis

Note: This parameter configures instance 2. It functions identically to SIM_GPS_ALT_OFS.

Simulated GPS 2 Byte Loss (SIM_GPS2_BYTELOS)

Description

SIM_GPS2_BYTELOS degrades the connection to the secondary GPS.

By dropping random bytes, you can simulate a loose cable or electrical noise on the UART line. This tests the GPS driver's ability to re-sync and the EKF's ability to handle packet loss.

Tuning & Behavior

• Default Value: 0%.

GPS 2 disable

Note: This parameter functions identically to SIM_GPS_DISABLE.

Simulated GPS 2 Altitude Drift (SIM_GPS2_DRFTALT)

Description

SIM_GPS2_DRFTALT makes the secondary GPS "Float" vertically.

GPS altitude is notoriously unreliable. This parameter adds a slow, continuous change to the reported height, allowing you to verify that the EKF (which usually trusts the Barometer for height) ignores the bad GPS altitude data.

Tuning & Behavior

• Default Value: 0.

Enable pullup after altitude wait

Note: This parameter functions identically to SIM_GPS1_ENABLE.

Simulation GPS 2 Glitch (SIM_GPS2_GLTCH)

Description

SIM_GPS2_GLTCH allows you to test dual-GPS configurations by "breaking" the secondary receiver.

By injecting a glitch into only one GPS, you can verify that the EKF successfully switches to the healthy receiver (if configured for GPS_AUTO_SWITCH = 1).

Simulated GPS 2 Heading (SIM_GPS2_HDG)

Description

SIM_GPS2_HDG sets the "True North" for the secondary GPS if it is a "Moving Baseline" unit.

By setting this to a value different from the actual vehicle heading, you can test how the autopilot handles "GPS Yaw" errors or alignment issues.

Tuning & Behavior

• Default Value: 0 (Matches vehicle heading).

Compass offsets in milligauss on the Z axis

Note: This parameter functions identically to SIM_GPS1_HDG_OFS.

GPS 2 Hz

Note: This parameter functions identically to SIM_GPS_HZ.

GPS jamming enable

Note: This parameter configures instance 2. It functions identically to SIM_GPS_JAM.

GPS 2 Lag

Note: This parameter functions identically to SIM_GPS_LAG_MS.

Simulation GPS 2 Lock Time (SIM_GPS2_LCKTIME)

Description

SIM_GPS2_LCKTIME allows you to simulate a scenario where one GPS gets a fix much later than the other, testing the autopilot's primary/secondary switchover logic.

Simulated GPS 2 Noise (SIM_GPS2_NOISE)

Description

SIM_GPS2_NOISE adds jitter to the secondary GPS.

Use this to test GPS Blending (GPS_AUTO_SWITCH = 2). You can make GPS 2 noisier than GPS 1 and verify that the autopilot correctly weights GPS 1 higher.

Tuning & Behavior

• Default Value: 0.

GPS 2 Num Satellites

Note: This parameter functions identically to SIM_GPS_NUMSATS.

GPS 2 Position

Note: This parameter functions identically to SIM_GPS_POS.

Tiltrotor type

Note: This parameter configures instance 2. It functions identically to SIM_GPS_TYPE.

GPS 2 Velocity Error

Note: This parameter configures instance 2. It functions identically to SIM_GPS_VERR.

Compass offsets in milligauss on the Z axis

Note: This parameter configures instance 3. It functions identically to SIM_GPS_ALT_OFS.

Enable pullup after altitude wait

Note: This parameter functions identically to SIM_GPS1_ENABLE.

Compass offsets in milligauss on the Z axis

Note: This parameter functions identically to SIM_GPS1_HDG_OFS.

Tiltrotor type

Note: This parameter configures instance 3. It functions identically to SIM_GPS_TYPE.

Compass offsets in milligauss on the Z axis

Note: This parameter configures instance 4. It functions identically to SIM_GPS_ALT_OFS.

Enable pullup after altitude wait

Note: This parameter functions identically to SIM_GPS1_ENABLE.

Compass offsets in milligauss on the Z axis

Note: This parameter functions identically to SIM_GPS1_HDG_OFS.

Tiltrotor type

Note: This parameter configures instance 4. It functions identically to SIM_GPS_TYPE.

Simulated GPS Accuracy (SIM_GPS_ACC)

Description

SIM_GPS_ACC defines the "Radius of Confusion" for the virtual GPS.

It sets the value reported in the MAVLink GPS_RAW_INT.h_acc field. While it doesn't always add physical noise to the position (see SIM_GPS_NOISE), it tells the EKF how much to trust the position.

Tuning & Behavior

• Default Value: 0.3 m.
• Recommendation: Set to 0.1 for "Ideal" GPS or 2.0 to simulate poor signal conditions.

Simulation GPS Altitude Offset (SIM_GPS_ALT_OFS)

Description

SIM_GPS_ALT_OFS injects a constant error into the GPS altitude. This is used to test if the EKF can handle significant differences between its primary altitude source (usually Barometer) and the GPS.

Simulation GPS Byte Loss (SIM_GPS_BYTELOSS)

Description

SIM_GPS_BYTELOSS simulates a flaky or noisy serial cable.

By randomly dropping a percentage of the data packets coming from the GPS, you can test how ArduPilot handles "Checksum Errors" and "Intermittent GPS" failures.

Tuning & Behavior

• Default Value: 0.
• Testing: Set to 10. You should see "GPS Glitch" or "GPS 1: Checksum error" messages in your GCS.

Simulation GPS Delay (SIM_GPS_DELAY)

Description

SIM_GPS_DELAY simulates the processing lag of a real GPS module.

Real GPS units don't report position instantly; there is a calculation delay.

Tuning & Behavior

• Default Value: 1.
• Testing: Increasing this can stress-test the EKF's ability to handle delayed measurements.

Simulation GPS Disable (SIM_GPS_DISABLE)

Description

SIM_GPS_DISABLE kills the GPS signal.

• 0: GPS Enabled.
• 1: GPS Disabled (No Fix).

Tuning & Behavior

• Default Value: 0.
• Testing: Use to test Optical Flow, T265 Realsense, or just plain AltHold/Stabilize flight without GPS assistance.

Simulation GPS Altitude Drift (SIM_GPS_DRIFTALT)

Description

SIM_GPS_DRIFTALT simulates the atmospheric drift often seen in low-cost GPS modules.

If the GPS reports that the drone is slowly "climbing" or "sinking" while it is actually sitting on the ground, the EKF must decide whether to believe the GPS or the Barometer. This parameter allows you to test that weighting logic.

Simulated GPS Glitch Offset (SIM_GPS_GLITCH)

Description

SIM_GPS_GLITCH simulates a "GPS Jump."

It adds a sudden, constant offset to the GPS coordinates. This is the best way to test if your EKF_CHECK_SCALE and failsafe settings are tight enough to detect a position jump before the drone flies away.

Tuning & Behavior

• Default Value: 0.
• Testing: Set to 10 or 20 meters while in LOITER mode and verify the drone triggers a failsafe rather than banking hard to chase the glitched position.

Simulation GPS Glitch X (SIM_GPS_GLITCH_X)

Description

SIM_GPS_GLITCH_X allows you to inject a GPS failure mid-flight.

By changing this parameter via MAVLink while flying in SITL, you can instantly shift the reported GPS position.

Tuning & Behavior

• Default Value: 0.
• Testing: Set to 20 while Loitering. The drone should lean hard to "correct" its position (actually moving away from the true target), then EKF might reject the glitch. Useful for testing EKF failsafe logic.

Simulated GPS Heading Enable (SIM_GPS_HDG)

Description

SIM_GPS_HDG allows the virtual GPS to report a "Moving Base" heading.

This is used for testing GPS-for-Yaw (Dual Antenna) setups in SITL. It tells the simulator to generate the relative position and heading messages that a real U-Blox or NMEA GPS would send when acting as a heading source.

Tuning & Behavior

• 0: None.
• 1: NMEA HDT sentence.
• 2: U-Blox RELPOSNED.
• 3: NMEA THS sentence.

Simulation GPS Update Rate (SIM_GPS_HZ)

Description

SIM_GPS_HZ sets the "Refresh Rate" of the simulated GPS.

• 5 (Default): Standard for most consumer GPS modules.
• 10: High performance (u-blox M8N/M9N).
• 50: Industrial RTK systems.

Tuning & Behavior

• Default Value: 5 Hz.
• Testing: Use this to verify that your GPS_RATE_MS and EKF settings can handle higher data rates without CPU overload.

Simulated GPS Jamming (SIM_GPS_JAM)

Description

SIM_GPS_JAM simulates a "Denial of Service" attack on your GPS.

When enabled, the GPS continues to report a "3D Fix" (usually), but the signal quality degrades, and the position may drift or freeze, mimicking the behavior of a jammed receiver.

Tuning & Behavior

• 0: Disabled.
• 1: Jamming Active.

Simulation GPS Jamming (SIM_GPS_JAM)

Description

SIM_GPS_JAM simulates the drone flying into an area with a GPS jammer.

• 0: Normal. GPS works as expected.
• 1: Jammed. The autopilot instantly loses GPS fix, as if the antenna were disconnected. Use this to verify that your drone's EKF correctly fails over to dead-reckoning or triggers an immediate "Land" failsafe.

Simulated GPS Lag (SIM_GPS_LAG_MS)

Description

SIM_GPS_LAG_MS simulates the time it takes for a GPS module to calculate your position and send it over the wire.

Real GPS units always have a delay (latency). This parameter is critical for EKF tuning; the EKF needs to know how "Old" the GPS data is so it can align it with the high-speed IMU data.

Tuning & Behavior

• Default Value: 120 ms.
• Recommendation: Set to match your hardware (e.g., U-Blox M8N is typically around 200ms, M9N is closer to 80-120ms).

Simulation GPS Lock Time (SIM_GPS_LOCKTIME)

Description

SIM_GPS_LOCKTIME simulates a "Cold Start."

In SITL, the GPS usually gets a fix instantly. This parameter forces the autopilot to wait for a realistic duration before the GPS reports a valid position. Useful for testing pre-arm procedures.

Simulated GPS Log Number (SIM_GPS_LOG_NUM)

Description

SIM_GPS_LOG_NUM allows you to replay a specific GPS track from a previous flight log.

If you have a DataFlash log (e.g., 00000012.BIN) where the GPS glitched or behaved weirdly, you can feed that exact GPS data into the simulator to see if the EKF can handle it better with different settings.

Tuning & Behavior

• Default Value: 0 (Disabled).
• Usage: Set SIM_GPS_TYPE to 7 (File) and set this parameter to the log index you want to replay.

Simulated GPS Noise (SIM_GPS_NOISE)

Description

SIM_GPS_NOISE adds random position jitter to the virtual GPS.

Unlike SIM_GPS_ACC (which only reports accuracy), this parameter actually moves the reported latitude/longitude/altitude by a random amount in every frame. This is the primary tool for testing how much GPS "Fuzz" your EKF can handle before the drone starts to wander or failsafes.

Tuning & Behavior

• Default Value: 0 (Perfect GPS).
• Recommendation: Set to 0.5 or 1.0 to simulate a realistic low-cost GPS in an open field. Set to 3.0+ to simulate urban canyon environments.

Simulation GPS Satellite Count (SIM_GPS_NUMSATS)

Description

SIM_GPS_NUMSATS allows you to simulate "Signal Shading" or poor sky visibility.

ArduPilot's EKF requires a minimum number of satellites to maintain a high-quality position fix. By reducing this value in SITL, you can test how the drone behaves when it enters a "Degraded GPS" state.

• 10 (Default): Healthy fix.
• 5: Poor fix. EKF may report warnings.
• 3: Fix lost. Drone will switch to non-GPS modes.

Simulation GPS Position Offset (SIM_GPS_POS)

Description

SIM_GPS_POS defines the mounting location of the virtual GPS antenna.

See GPS_POS for details on why antenna offsets are critical for flight stability.

Simulation GPS Type (SIM_GPS_TYPE)

Description

SIM_GPS_TYPE tells the simulator which "Language" to use when sending data to the autopilot.

• 1: u-blox (Standard). The most common GPS type.
• 5: NMEA. Generic serial data.
• 9: DroneCAN. Simulates a CAN-bus GPS.
• 14: MAVLink.

Simulation GPS Velocity Error (SIM_GPS_VERR)

Description

SIM_GPS_VERR simulates a GPS receiver that reports incorrect speeds.

This is a common failure mode in real-world "Urban Canyons," where signal multipath can cause the GPS to think the drone is moving at 2 m/s even when it is perfectly still. This parameter helps you test the EKF's ability to reject bad velocity data and rely more on the accelerometers.

Simulation Gripper Enable (SIM_GRPE_ENABLE)

Description

SIM_GRPE_ENABLE activates a virtual robotic gripper.

This allows you to test "Pick and Place" missions in SITL. When enabled, the drone can physically attach to objects (like a virtual package) and carry them through the air, accounting for the added weight and inertia in the physics model.

Simulated EPM Gripper Pin (SIM_GRPE_PIN)

Description

SIM_GRPE_PIN links the virtual EPM magnet to an output channel.

Gripper Servo Sim Enable (SIM_GRPS_ENABLE)

Description

SIM_GRPS_ENABLE adds a functional virtual gripper to the drone.

This allows you to test "Cargo Hold" operations. The simulator models a servo-driven jaw that can pick up and drop a 1kg load when on the ground.

Tuning & Behavior

• 0: Disabled.
• 1: Enabled.

Gripper Grab PWM (SIM_GRPS_GRAB)

Description

SIM_GRPS_GRAB sets the "Closed" position for the virtual gripper.

Gripper Servo Pin (SIM_GRPS_PIN)

Description

SIM_GRPS_PIN connects the virtual gripper to a flight controller output.

Set this to match your SERVOx_FUNCTION = 28 (Gripper) channel. When ArduPilot moves that servo, the simulator will open or close the virtual jaws.

Tuning & Behavior

• Default Value: -1 (Disabled).

Gripper Release PWM (SIM_GRPS_RELEASE)

Description

SIM_GRPS_RELEASE sets the "Open" position for the virtual gripper.

Gripper Reverse (SIM_GRPS_REVERSE)

Description

SIM_GRPS_REVERSE swaps the open and closed states of the virtual jaws.

Simulation Gyro 1 Bias (SIM_GYR1_BIAS)

Description

SIM_GYR1_BIAS simulates "Gyro Drift."

Real-world gyroscopes are sensitive to temperature and time. If you leave a drone sitting on a table, the reported rotation rate might not be exactly zero. This drift is the primary cause of "Horizon Tilt" in flight. ArduPilot's EKF is designed to learn and cancel this drift.

Tuning & Behavior

• Default Value: 0.
• Testing: Set to 1.0 (1 degree per second). You can watch the EKF "innovations" in your logs as the autopilot detects and attempts to compensate for this fake drift.

Simulated Gyroscope 1 Noise (SIM_GYR1_RND)

Description

SIM_GYR1_RND injects artificial noise into the simulated primary gyroscope.

This is used to test how "twitchy" or unstable the drone's attitude control becomes when the gyro data is imperfect. High noise levels can cause the drone to oscillate or lose orientation entirely.

The Engineer's View

Adds Gaussian noise (σ) to the body-frame rotational rate:
$$ \omega\_{read} = \omega\_{true} + \mathcal{N}(0, \text{SIM\_GYR1\_RND}) $$

Tuning & Behavior

• Default Value: 0
• Effect of Increasing: The drone's attitude (roll/pitch/yaw) will appear to vibrate or "jitter" in the GCS HUD, and the EKF may trigger "high gyro noise" warnings.

Simulation Gyro 1 Scale (SIM_GYR1_SCALE)

Description

SIM_GYR1_SCALE simulates a sensitivity error on the rotation axis.

If you rotate the drone by exactly 360 degrees, a sensor with a scale error might report 365 or 355 degrees. This is important for verifying high-rate aerobatic performance.

Simulation Gyro 2 Bias (SIM_GYR2_BIAS)

Description

SIM_GYR2_BIAS simulates drift on the secondary IMU.

See SIM_GYR1_BIAS for details.

Gyro 2 motor noise factor

Note: This parameter functions identically to SIM_GYR1_RND.

Simulation Gyro 2 Scale (SIM_GYR2_SCALE)

Description

SIM_GYR2_SCALE simulates sensitivity errors on the secondary IMU.

See SIM_GYR1_SCALE for details.

Simulation Gyro 3 Bias (SIM_GYR3_BIAS)

Description

SIM_GYR3_BIAS simulates drift on the tertiary IMU.

See SIM_GYR1_BIAS for details.

Gyro 3 motor noise factor

Note: This parameter functions identically to SIM_GYR1_RND.

Gyro 3 scaling factor

Note: This parameter configures instance 3. It functions identically to SIM_GYR1_SCALE.

Fourth Gyro bias on Z axis

Note: This parameter configures instance 4. It functions identically to SIM_GYR1_BIAS.

Gyro 4 motor noise factor

Note: This parameter functions identically to SIM_GYR1_RND.

Gyro 4 scaling factor

Note: This parameter configures instance 4. It functions identically to SIM_GYR1_SCALE.

Fifth Gyro bias on Z axis

Note: This parameter configures instance 5. It functions identically to SIM_GYR1_BIAS.

Gyro 5 motor noise factor

Note: This parameter functions identically to SIM_GYR1_RND.

Gyro 5 scaling factor

Note: This parameter configures instance 5. It functions identically to SIM_GYR1_SCALE.

Simulated Gyroscope Failure Mask (SIM_GYR_FAIL_MSK)

Description

SIM_GYR_FAIL_MSK kills specific gyroscopes in the simulator.

This is critical for testing the "vibration failsafe" and EKF lane switching logic.

• Bit 0 (1): Fail Gyro 1
• Bit 1 (2): Fail Gyro 2
• Bit 2 (4): Fail Gyro 3

Tuning & Behavior

• Default Value: 0
• Recommendation: Use in conjunction with SIM_ACC_FAIL_MSK to simulate a complete IMU failure.

Simulated Gyroscope File Read/Write (SIM_GYR_FILE_RW)

Description

SIM_GYR_FILE_RW works exactly like SIM_ACC_FILE_RW but for the gyroscope.

Use this to replay real-world gyro noise (propeller vibration) into the simulator. This is the gold standard for testing Harmonic Notch Filter settings without risking a crash.

Tuning & Behavior

• Default Value: 0.
• Procedure:
  1. Set to 2 (Write).
  2. Fly/Hover for 1 minute.
  3. Copy the generated file to your SITL directory.
  4. Set to 1 (Read) and run SITL.

Simulated IE24 Fuel Cell Enable (SIM_IE24_ENABLE)

Description

SIM_IE24_ENABLE adds a virtual Hydrogen Fuel Cell to the simulation.

This allows you to test the telemetry feedback (tank pressure, stack voltage, error states) of an Intelligent Energy 2.4kW unit without needing the expensive hardware.

Tuning & Behavior

• 0: Disabled.
• 1: Enabled.

Simulated IE24 Error Code (SIM_IE24_ERROR)

Description

SIM_IE24_ERROR simulates a hardware failure.

By setting this to a valid IE24 error bitmask, you can verify that the GCS displays the correct warning message (e.g. "Low Hydrogen Pressure" or "Stack Over-temp").

Tuning & Behavior

• Default Value: 0.

Simulated IE24 State (SIM_IE24_STATE)

Description

SIM_IE24_STATE overrides the fuel cell logic.

• 0: Auto (Normal operation).
• 1: Starting.
• 2: Running.
• 4: Fault.

Tuning & Behavior

• Default Value: 0.

Simulated IMU 1 Thermal Enable (SIM_IMUT1_ENABLE)

Description

SIM_IMUT1_ENABLE activates the simulated heat-up process for the first IMU.

When enabled, the IMU's reported temperature will follow the curve defined by SIM_IMUT_START, END, and TCONST. This is useful for verifying that your INS_TCAL1_ parameters (learned during a real temp cal) correctly remove the bias drift in the simulator.

Tuning & Behavior

• 0: Disabled (IMU stays at constant temperature).
• 1: Enabled.

Simulation IMU Temperature Max (SIM_IMUT1_TMAX)

Description

SIM_IMUT1_TMAX defines the upper bound for the IMU thermal model.

Simulation IMU Temperature Min (SIM_IMUT1_TMIN)

Description

SIM_IMUT1_TMIN defines the lower bound for simulating IMU thermal noise and bias shifts.

Enable pullup after altitude wait

Note: This parameter functions identically to SIM_IMUT1_ENABLE.

Temperature calibration max

Note: This parameter functions identically to SIM_IMUT1_TMAX.

Temperature calibration min

Note: This parameter functions identically to SIM_IMUT1_TMIN.

Enable pullup after altitude wait

Note: This parameter functions identically to SIM_IMUT1_ENABLE.

Temperature calibration max

Note: This parameter functions identically to SIM_IMUT1_TMAX.

Temperature calibration min

Note: This parameter functions identically to SIM_IMUT1_TMIN.

Enable pullup after altitude wait

Note: This parameter functions identically to SIM_IMUT1_ENABLE.

Temperature calibration max

Note: This parameter functions identically to SIM_IMUT1_TMAX.

Temperature calibration min

Note: This parameter functions identically to SIM_IMUT1_TMIN.

Enable pullup after altitude wait

Note: This parameter functions identically to SIM_IMUT1_ENABLE.

Temperature calibration max

Note: This parameter functions identically to SIM_IMUT1_TMAX.

Temperature calibration min

Note: This parameter functions identically to SIM_IMUT1_TMIN.

Simulated IMU Final Temperature (SIM_IMUT_END)

Description

SIM_IMUT_END sets the target temperature that the flight controller will eventually reach after it has been running for a while (due to CPU heat and internal electronics).

Tuning & Behavior

• Default Value: 45 °C.

Simulated IMU Fixed Temperature (SIM_IMUT_FIXED)

Description

SIM_IMUT_FIXED forces the virtual IMU to stay at a specific temperature.

If set to a non-zero value, the IMU temperature will not follow the curve defined by SIM_IMUT_START and SIM_IMUT_END. This is useful for testing sensor bias at a specific operating point without waiting for the heat-up cycle.

Tuning & Behavior

• 0: Disabled (Use dynamic thermal curve).
• Non-Zero: Fixed temperature in Celsius.

Simulated IMU Start Temperature (SIM_IMUT_START)

Description

SIM_IMUT_START defines the "Ambient Temperature" when the simulator starts.

SITL can simulate the heating of the flight controller over time. This parameter sets the baseline. If you want to test how your drone handles a sub-zero cold start, you can set this to -10.

Tuning & Behavior

• Default Value: 25 °C.
• Usage: Use this in conjunction with SIM_IMUT_END and SIM_IMUT_TCONST to create a thermal warm-up profile.

Simulated IMU Thermal Time Constant (SIM_IMUT_TCONST)

Description

SIM_IMUT_TCONST determines how fast the flight controller heats up.

It defines the "Slope" of the temperature curve. A value of 300 seconds (5 minutes) means the drone will reach its steady-state temperature fairly slowly, mimicking a real flight controller on a workbench.

The Mathematics

The temperature $T(t)$ at time $t$ is modeled as an exponential approach:

$$ T(t) = T\_{start} + (T\_{end} - T\_{start}) \times (1 - e^{-t / \tau}) $$

Where $\tau$ is the SIM_IMUT_TCONST.

Simulated IMU Count (SIM_IMU_COUNT)

Description

SIM_IMU_COUNT sets the number of virtual internal sensors.

Modern flight controllers often have 2 or 3 IMUs for safety. This parameter allows SITL to mimic that redundancy. You can then use SIM_ACCELx_FAIL to kill one sensor and see how the autopilot handles it.

Tuning & Behavior

• Default Value: 2.
• Recommendation: Set to 2 or 3 to test EKF lane switching logic.
• Reboot Required: Yes.

Simulated IMU Orientation (SIM_IMU_ORIENT)

Description

SIM_IMU_ORIENT sets the physical "Heading" of the virtual sensors.

By default (0), the IMU is aligned with the drone's nose. If you want to test how ArduPilot handles an IMU that is mounted upside down or rotated 90 degrees, you can change this parameter and then verify that you can still calibrate and fly successfully using AHRS_ORIENTATION.

Tuning & Behavior

• Default Value: 0 (None).
• Recommendation: Leave at 0 for standard tests. Use values like 8 (Roll 180) to test an inverted flight controller.

Simulation IMU Position Offset (SIM_IMU_POS)

Description

SIM_IMU_POS simulates an IMU that is not mounted exactly at the center of gravity (COG).

When a drone rotates, any sensor away from the COG experiences "Centripetal Acceleration." If ArduPilot doesn't know about this offset (configured via INS_POS_X/Y/Z), the EKF will get confused and report incorrect velocity. This parameter allows you to test the compensation for these "Lever Arm" effects.

Simulation Initial Alt Offset (SIM_INIT_ALT_OFS)

Description

SIM_INIT_ALT_OFS allows you to start the simulation with the drone at a specific height above the ground. Useful for testing in-air resets or high-altitude drop launches.

Simulated Initial Latitude Offset (SIM_INIT_LAT_OFS)

Description

SIM_INIT_LAT_OFS allows you to test what happens if the "map" shifts under the drone.

It adds a constant offset to the GPS position reported by the simulator, effectively moving the world origin.

Tuning & Behavior

• Default Value: 0.

Simulated Initial Longitude Offset (SIM_INIT_LON_OFS)

Description

SIM_INIT_LON_OFS shifts the GPS longitude origin. See SIM_INIT_LAT_OFS.

Tuning & Behavior

• Default Value: 0.

Simulated INS Noise Throttle Min (SIM_INS_THR_MIN)

Description

SIM_INS_THR_MIN defines when the "Shaking" starts.

Real drones vibrate more when the motors are spinning fast. This parameter tells SITL to only add motor-induced noise when the throttle is above a certain percentage (e.g. 10%). On the ground at zero throttle, the IMUs will remain clean.

Tuning & Behavior

• Default Value: 0.1 (10% throttle).

Simulated JSON Master (SIM_JSON_MASTER)

Description

SIM_JSON_MASTER enables the "External Physics" bridge.

Instead of SITL calculating the drone's movements, it can send the motor outputs to a high-fidelity simulator (like Gazebo, AirSim, or Webots) and get the position/sensor data back over a JSON socket. This parameter sets the IP address of that external simulator.

Tuning & Behavior

• Default Value: 127.0.0.1 (Localhost).
• Usage: Only active if the SITL build includes the JSON backend.

Simulation LED Layout (SIM_LED_LAYOUT)

Description

SIM_LED_LAYOUT defines the number and position of virtual status LEDs in SITL. This is primarily used for verifying LED driver logic and patterns (like those for the SkyViper or ProfiLED) in a simulated environment.

Simulated Loop Delay (SIM_LOOP_DELAY)

Description

SIM_LOOP_DELAY simulates a "Slow Processor."

If you set this to 5ms, every single logic loop in the autopilot will take 5ms longer than usual. This is a great way to test the safety margins of your loop rate and see at what point the drone becomes unflyable due to latency.

Simulated Magnetometer 1 Device ID (SIM_MAG1_DEVID)

Description

SIM_MAG1_DEVID sets the unique hardware identifier for the virtual compass.

This is usually read-only or managed by SIM_MAG_SAVE_IDS. However, developers can manually set this to test how the OS handles specific sensor types (e.g. simulating a specific I2C address conflict).

Tuning & Behavior

• Default Value: 0 (Auto-generated).

Simulation Magnetometer 1 Diagonal (SIM_MAG1_DIA)

Description

SIM_MAG1_DIA simulates "Soft Iron" interference.

Soft iron effects are caused by materials that distort magnetic fields but are not themselves magnets (like iron or nickel). This distorts the magnetic "sphere" into an "ellipsoid." ArduPilot's advanced calibration routine calculates these diagonal scaling factors to fix this distortion.

Simulation Compass 1 Failure (SIM_MAG1_FAIL)

Description

SIM_MAG1_FAIL kills the first compass sensor.

• 0: Healthy.
• 1: Failed. The sensor stops reporting data.

Tuning & Behavior

• Testing: Use this to verify that your drone successfully fails over to the second compass (if available) or switches to GSF (GPS-based yaw) without crashing.

Simulation Magnetometer 1 Off-Diagonal (SIM_MAG1_ODI)

Description

SIM_MAG1_ODI simulates complex magnetic distortions.

While SIM_MAG1_DIA scales the X, Y, and Z axes independently, ODI (Off-Diagonal) terms simulate how a magnetic field in one axis (e.g. X) can bleed into another axis (e.g. Y). This represents a highly non-linear or asymmetric magnetic environment.

Simulation Magnetometer 1 Offset (SIM_MAG1_OFS)

Description

SIM_MAG1_OFS simulates "Hard Iron" interference.

Hard iron effects are caused by static magnetic fields on the drone (like a magnetized screw or the metal frame). This offsets the magnetic reading in a constant direction. This is what you are calibrating when you perform the "Compass Dance."

Tuning & Behavior

• Default Value: 0.
• Testing: Set to 50. The drone will report "Compass Variance" until you perform a compass calibration in SITL.

Simulated Magnetometer 1 Orientation (SIM_MAG1_ORIENT)

Description

SIM_MAG1_ORIENT sets the physical rotation of the virtual compass.

If you simulate a GPS/Compass module mounted with the arrow pointing backwards (Yaw 180), you must set this parameter to match.

Tuning & Behavior

• Default Value: 0 (None).

Simulated Magnetometer 1 Scaling (SIM_MAG1_SCALING)

Description

SIM_MAG1_SCALING simulates a mis-calibrated compass.

By setting this to 1.1 or 0.9, you can test if the "Compass Motel" (onboard calibration) or the EKF can learn and correct for the scale factor error.

Tuning & Behavior

• Default Value: 1.0.

Airspeed ID

Note: This parameter functions identically to SIM_MAG1_DEVID.

Simulation Magnetometer 2 Diagonal (SIM_MAG2_DIA)

Description

SIM_MAG2_DIA simulates a distorted magnetic field on the secondary compass.

See SIM_MAG1_DIA for details.

MAG2 Failure

Note: This parameter functions identically to SIM_MAG1_FAIL.

Simulation Magnetometer 2 Off-Diagonal (SIM_MAG2_ODI)

Description

SIM_MAG2_ODI simulates complex magnetic twisting on the secondary compass.

See SIM_MAG1_ODI for details.

Simulation Magnetometer 2 Offset (SIM_MAG2_OFS)

Description

SIM_MAG2_OFS simulates hard-iron interference on the secondary compass.

This is useful for testing the EKF's ability to handle inconsistent compass data. If Compass 1 is perfect and Compass 2 has a massive offset, the EKF should (ideally) reject Compass 2 or learn the offset.

Tuning & Behavior

• Default Value: 0.
• Testing: Set to 100 to simulate a magnetized screw near the second GPS puck.

Camera Orientation

Note: This parameter functions identically to SIM_MAG1_ORIENT.

RPM scaling

Note: This parameter functions identically to SIM_MAG1_SCALING.

Airspeed ID

Note: This parameter functions identically to SIM_MAG1_DEVID.

Note: This parameter configures instance 3. It functions identically to SIM_MAG1_DIA.

MAG3 Failure

Note: This parameter functions identically to SIM_MAG1_FAIL.

Note: This parameter configures instance 3. It functions identically to SIM_MAG1_ODI.

Simulation Magnetometer 3 Offset (SIM_MAG3_OFS)

Description

SIM_MAG3_OFS simulates hard-iron interference on the third compass.

See SIM_MAG1_OFS for details.

Camera Orientation

Note: This parameter functions identically to SIM_MAG1_ORIENT.

RPM scaling

Note: This parameter functions identically to SIM_MAG1_SCALING.

Airspeed ID

Note: This parameter functions identically to SIM_MAG1_DEVID.

Airspeed ID

Note: This parameter functions identically to SIM_MAG1_DEVID.

Airspeed ID

Note: This parameter functions identically to SIM_MAG1_DEVID.

Airspeed ID

Note: This parameter functions identically to SIM_MAG1_DEVID.

Airspeed ID

Note: This parameter functions identically to SIM_MAG1_DEVID.

Simulation Magnetic Anomaly (SIM_MAG_ALY)

Description

SIM_MAG_ALY simulates flying over a large iron object (like a bridge or underground pipe).

Unlike MAG_OFS, which is attached to the drone, MAG_ALY is a disturbance in the "World" that only affects the drone when it is in a specific location. Useful for testing the EKF's resilience to sudden, external heading shifts.

Simulated Magnetic Anomaly Height (SIM_MAG_ALY_HGT)

Description

SIM_MAG_ALY_HGT creates a virtual "Magnetic Distortion Field" at a specific altitude.

This is useful for simulating flying near a large steel structure (like a bridge or tower). You can test if the EKF correctly rejects the bad compass data or if the drone starts to toilet-bowl.

Tuning & Behavior

• Default Value: 0.

Simulation Compass Delay (SIM_MAG_DELAY)

Description

SIM_MAG_DELAY simulates slow compass updates or high-latency I2C buses.

Real compasses often sample slower than the EKF's loop rate. This parameter tests if the EKF can correctly align delayed compass samples with the corresponding IMU poses.

Simulation Compass Motor Interference (SIM_MAG_MOT)

Description

SIM_MAG_MOT simulates "CompassMot" effects.

In real drones, the high-current wires going to the motors produce magnetic fields that can bias the compass. As you increase throttle, the compass heading "twists." This parameter allows you to simulate this effect to test the efficacy of the CompassMot calibration.

Tuning & Behavior

• Default Value: 0.
• Testing: Set to 0.5. Perform a full throttle punch in Loiter. The drone will likely rotate (yaw) unintentionally as the compass drifts under load.

Simulated Magnetometer Noise (SIM_MAG_NOISE)

Description

SIM_MAG_NOISE adds random jitter to the compass readings.

Real compasses are very clean sensors, but they are affected by surrounding electronics. This parameter simulates that background electromagnetic noise.

Tuning & Behavior

• Default Value: 0.
• Recommendation: Set to 5-10 mGauss for realistic testing.

Simulated Magnetometer Noise (SIM_MAG_RND)

Description

SIM_MAG_RND adds static fuzz to the compass readings.

Tuning & Behavior

• Default Value: 0.
• Testing: Increase this to see how much noise the EKF can tolerate before triggering a "Compass Variance" error.

Simulated Magnetometer Save IDs (SIM_MAG_SAVE_IDS)

Description

SIM_MAG_SAVE_IDS makes the virtual compasses persistent.

Normally, every time you restart SITL, it generates new random "Device IDs" for the sensors. This forces you to re-calibrate the compass every time. If you enable this, the simulator saves the IDs, allowing you to keep your calibration data.

Tuning & Behavior

• 0: Disabled (New IDs on boot).
• 1: Enabled (Save IDs).

Simulation Odometry Enable (SIM_ODOM_ENABLE)

Description

SIM_ODOM_ENABLE activates a virtual Visual Odometry (VO) sensor.

This simulates a camera-based system (like an Intel Realsense) that tracks the drone's position by looking at the ground. Useful for testing autonomous navigation in GPS-denied environments without needing a full Vicon setup.

SIM-on-Hardware Output Mask (SIM_OH_MASK)

Description

SIM_OH_MASK allows "Hardware-in-the-Loop" behavior without external software.

If you flash the SITL binary onto a real Pixhawk ("Sim on Hardware"), the physics run on the CPU, but the servo outputs are normally disabled. This mask enables specific physical pins so you can drive real servos or motors while flying a virtual drone.

Tuning & Behavior

• Default Value: 0 (All outputs disabled).
• Bit 0 (1): Enable Servo 1.
• Bit 1 (2): Enable Servo 2.

SIM-on-Hardware Relay Mask (SIM_OH_RELAY_MSK)

Description

SIM_OH_RELAY_MSK enables physical relay pins during "Sim on Hardware."

Tuning & Behavior

• Default Value: 0.

Simulated Original Position (Altitude) (SIM_OPOS_ALT)

Description

SIM_OPOS_ALT sets the spawn height Above Mean Sea Level (AMSL).

Tuning & Behavior

• Default Value: 584.0 m (Canberra elevation).
• Important: If you change Lat/Lng to a coastal city but leave this at 584m, your drone will spawn 584m in the air!

Simulated Original Position (Heading) (SIM_OPOS_HDG)

Description

SIM_OPOS_HDG sets the direction the vehicle faces when it spawns.

• 0: North
• 90: East
• 180: South
• 270: West

Tuning & Behavior

• Default Value: 353.0 degrees.
• Recommendation: Align this with the "virtual runway" at your test site to make takeoff easier.

Simulated Original Position (Latitude) (SIM_OPOS_LAT)

Description

SIM_OPOS_LAT sets the home location where your drone spawns in the simulator.

• Default: CMAC (Canberra Model Aircraft Club) in Australia.
• Usage: Change this to your local flying field's coordinates to test missions in a familiar environment.

Tuning & Behavior

• Default Value: -35.363261 (Canberra).
• Recommendation: Use a tool like Mission Planner's "Set Home" feature, which updates this parameter automatically.

Simulated Original Position (Longitude) (SIM_OPOS_LNG)

Description

SIM_OPOS_LNG sets the starting longitude for the simulation.

Tuning & Behavior

• Default Value: 149.165230 (Canberra).

Simulated OSD Columns (SIM_OSD_COLUMNS)

Description

SIM_OSD_COLUMNS defines the width of the virtual OSD screen.

Tuning & Behavior

• Default Value: 30 columns.

Simulated OSD Rows (SIM_OSD_ROWS)

Description

SIM_OSD_ROWS defines the height of the virtual OSD screen.

This is used for testing MSP (MultiWii Serial Protocol) OSD layouts in SITL. By changing this, you can simulate different goggle resolutions or display types.

Tuning & Behavior

• Default Value: 16 rows.
• Common Settings: 13 or 16 rows for standard analog/digital systems.