Sensor Calibrations

Speed Sensor Calibration

The ANELLO Maritime INS uses input from paddle wheels, ultrasonic sensors, or doppler velocity logs as a speed aiding source. These sensors typically have a speed-dependent scale factor which needs to be accounted for, and this can vary from boat-to-boat.

Each time the ANELLO Maritime INS is installed on a new boat model, the boat’s speed sensor needs to be calibrated relative to the boat’s motor percentage. To calibrate the speed sensor:

  1. Launch boat into water with as little currents as possible

  2. Power on the ANELLO Maritime INS while boat is stationary and allow ~30s to gain GPS

  3. Enable Speed Sensor Auto-Calibration Control with either the NMEA0183 message detailed here or the NMEA2000 message detailed here

  4. Perform “out and back” mission of at least 30 second duration per leg at each of the following percentages of the vehicle’s max speed: 20%, 40%, 60%, 80%, 100%

    1. If there are constant currents, performing the “out and backs” with and against the current is ideal

    2. Ensure there are no other major sources of currents (e.g. other boats) during the “out and backs” as this will alter the calculation.

    3. Increasing the number of out-and-back data points across the full speed range improves calibration accuracy.

  5. Once “out and backs” are complete, disable the auto calibration mode through the NMEA0183 message detailed here or the NMEA2000 message detailed here

  6. For any questions or assistance with the calibration procedure, please download the logs from the ANELLO Maritime INS (using the instructions under Data Collection and Visualization ) and send to ANELLO along with your inquiry.

Re-calibration of the speed sensor is necessary if any of the following conditions are met:

  • The boat type/model is changed.

  • The location of the speed sensor is changed.

  • The speed sensor type/model is changed.

  • The motor type/model is changed.

  • The loaded weight of the boat is significantly changed (e.g. the weight of the boat is doubled due to a payload).

  • Otherwise, the calibration does not need to be redone for boats of the same model, with the same sensor models and similar installation positions.

Note

Reach out to support@anellophotonics.com for speed sensor recommendations

(Optional) External Magnetometer Calibration

In the case that you will be supplying the ANELLO Maritime INS with data from an external magnetometer via NMEA0183 VHW input or the ANELLO Proprietary Auxiliary RPH messages in NMEA0183 or NMEA2000 you may conduct an optional external magnetometer calibration procedure to improve the accuracy of the reported heading.

Calibration procedures will seek to gain visibility into all potential headings and motor percentages during operation. If you will be using an electric motor, it is recommended to limit the amount of ramping of the motor during the data collection period, to minimize abrupt changes in the induced magnetic field of the motor.

To calibrate the external magnetometer:

  1. Launch boat into water.

  2. Power on the ANELLO Maritime INS while boat is stationary and allow ~30s to gain GPS.

  3. Perform a “figure-eight” or “flower” shaped mission at a series of increasing motor percentages, maintaining a constant motor percentage per each figure-eight or flower.

  4. Once the calibration mission is complete, power off the ANELLO Maritime INS.

  5. After you finish other water missions, download the logs from the ANELLO Maritime INS (using the instructions under Data Collection and Visualization ) and send to ANELLO.

  6. ANELLO will instruct on updating the external magnetometer calibration values.

Re-calibration of the external magnetometer is necessary if any of the following conditions are met:

  • The boat type/model is changed.

  • The external magnetometer type/model is changed.

  • The location of the external magnetometer is changed.

  • The motor type/model is changed.

  • The magnetic components of the boat are significantly changed.