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  • ROV Locator
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  • General Specifications Mk III
  • System Variants
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    • Sound Reflection and Absorption
    • Multipath
    • Ping Length
    • What to Do About Multipath and Other Issues
    • Clock Drift Expectations
    • Accuracy Expectations
      • Accuracy Test: Topside GPS
      • Accuracy Test: 110 Meter Slant Range
      • Accuracy Test: 295 Meter Slant Range
    • Operation in a Pool
  • Autosync Option (Mk II Only)
    • Autosync Mission Scenarios and Mission Suitability
    • Autosync Availability
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  • ROVL Channels (Autosync only; Operating Multiple Units in Proximity)
  • ROVL Coordinate Systems and Angles
    • Definitions
    • NED or “Compass” vs. ENU or “Math” Angles
    • Math to Compass Frame Conversions
    • Transducer Down Orientation
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    • Receiver/Transceiver Orientation Frames
    • Best Operating Envelope
  • Communicating With the ROVL
    • Serial Parameters
    • Packet Format
    • Messages from ROVL to Host
      • $USRTH Receiver-Transmitter Relative Angles Message
      • $USINF Information Message
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    • Messages from Host to ROVL
      • NMEA-Format Messages to Receiver
      • Valid Commands from Host to ROVL
  • Inertial Measurement Unit (IMU)
    • How To Tell Which IMU is Active
    • Mk II IMU Modes and Calibration
      • Mk II IMU Calibration Background
      • Mk II IMU Calibration General Procedures
    • CIMU Calibration Background
      • CIMU Magnetometer Calibration
      • CIMU Accelerometer Calibration
      • CIMU Gyro Calibration
  • Operating and Accuracy Considerations
  • Multi-Unit Operation (Swarms)
    • Multi-Unit 1:1
    • Multi-Unit 1:2
    • Multi-Unit 2x1:1
    • Multi-Unit n:1 (fixed transmitter)
    • Multi-Unit n:1 (mobile transmitter)
  • ROVL Mounting and Wiring
    • ROV/Deepside Mounting
    • Topside Mounting
    • Simple Topside Deployment Fixture
    • Wiring Notes
    • Electrical Noise
    • USB Interface using Blue Robotics BLUART Board
  • Mechanical Drawings
    • Mounting Footprint and Envelope, "S" Package
    • Mounting Footprint ("P" Package Mk II and Mk III)
    • Envelope Drawing. "P" Package ROVL Mk II Transmitter and Receiver, Mk III Transponder
  • Appendix: Math for Computing Remote Latitude/Longitude
    • Receiver & GPS at Topside and Transmitter Deepside
    • Transmitter & GPS Topside and Receiver Deepside
  • Appendix: Factory Usage Command Set
  • Troubleshooting
    • How to Tell if Your Mk II Receiver is Working
    • How to tell if your Mk II Transmitter is working
    • What to do when you find an unresolvable problem when troubleshooting
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  1. Inertial Measurement Unit (IMU)

CIMU Calibration Background

PreviousMk II IMU Calibration General ProceduresNextCIMU Magnetometer Calibration

Last updated 6 months ago

The Mk III Transceiver contains an IMU (called the "Cerulean IMU") that has internal magnetometers, accelerometers and gyros. These sensors are imperfect and can have manufacturing bias and linearity errors. Additionally, external magnetic disturbances can cause the magnetometers to make a bad estimate of magnetic north. Calibration mitigates the effect of these factors.

The gyros and accelerometers are subject to slight aging effects, and to temperature effects. Generally, you really only need to calibrate these every three to six months.

The magnetometers are subject to variations in the Earth's magnetic field strength and to magnetic disturbances due to electrical currents and and nearby soft iron or other ferrous objects. The closer a disturbance source, the smaller it can be and still affect north-finding. Generally, you should calibrate the magnetometers when you move the system a geographically significant distance (e.g., 50 km or more), or to an magnetically different location.

See the following sections on CIMU calibration procedures.

CIMU Calibration is started by clicking the "CIMU Calibrator" button (highlighted). This button is only enabled if the currently connected device has a CIMU.