Inertial Measurement Unit (IMU)

Learn more about MarFac’s IMUs:

• POS MV WaveMaster II
• POS MV OceanMaster
• POS MV Elite
• Dynamic Inclinometer

POS MV

Sources/Usage: Public Domain. View Media Details

The POS MV combines data from Global Navigation Satellite System (GNSS), angular rate and acceleration data from an IMU, and heading data from GNSS Azimuth Measurement System (GAMS). These systems provide robust and accurate positioning and orientation with a full 6 degrees of freedom.

The POS MV is used in conjunction with shipboard mapping systems, such as multibeam sonar and interferometric sonar, to provide high-resolution acceleration and orientation information along with the associated geospatial location information.

WaveMaster II with Small Form Factor POS Computer System (PCS)

Currently, this system is dedicated to the PCMSC personal watercraft mapping system “Kelp Fly”

Specifications

• Manufacturer -  Applanix
• Model - POS MV WaveMaster II with Small Form Factor POS Computer System (PCS)
• Weight - PCS 2.5 kg; IMU 2.5 kg
• Dimensions -
  
  PCS (Small Form Factor): L = 167 mm, W = 185 mm, H = 68 mm
  
  IMU: L = 158 mm, W = 158 mm, H = 124 mm
• Power Requirements - DC 10-34 V, 35 W (peak)

Sources/Usage: Public Domain. View Media Details

Operational Characteristics

Maximum real-time data output of 200 Hz over ethernet

Accuracy specifications with Inertially Aided Real-Time Kinematic (IARTK) corrections

• Roll, Pitch accuracy: 0.02° (1 sigma)
• Heading Accuracy: 0.03° (1 sigma) with 2 m antenna baseline, 0.015° (1 sigma) with 4 m baseline
• Positioning Accuracy:
  
  Horizontal: ±(8 mm + 1 ppm x baseline length)
  
  Vertical: ±(15 mm + 1 ppm x baseline length)
  
  Note: IAPPK accuracies assume 1 m IMU-GNSS antenna offset 
• Heave Accuracy: 5 cm or 5% (whichever is greater) for periods of 20 s or less 

Additional Equipment required

Two GNSS antennas rigidly mounted so that they have more than 1 m (greater than 2 m recommended) but less than 5 m horizontal separation distance between them.

POS MV OceanMaster with Submersible Inertial Measurement Unit (Type 45 IMU)

Sources/Usage: Public Domain. View Media Details

The submersible enables the sensor to be located near or directly on the sonar transducer head to reduce errors caused by relative motion between IMU and sonar head or by inaccuracies of lever-arm measurements.

Specifications

• Manufacturer -  Applanix
• Model - POS MV V5 POS Computer System (PCS) with type 45 submersible IMU
• Weight - PCS 3.9 k; IMU 3.4 kg
• Dimensions -
  
  PCS: 19-inch rack mount chassis, 1U high (442 mm X 46 mm X 356 mm)
  
  IMU:  Ø100 mm (base plate Ø132 mm), height 105 mm
• Power Requirements - AC 120/230 V, 50/60 Hz, auto-switching 40 W

Operational Characteristics

Maximum real-time data output of 200 Hz over ethernet

Accuracy specifications with Inertially Aided Real-Time Kinematic (IARTK) corrections

• Roll, Pitch accuracy: 0.01° (1 sigma )
• Heading Accuracy: 0.02° (1 sigma) with 2 m antenna baseline, 0.01° (1 sigma) with 4 m baseline
• Positioning Accuracy:
  
  Horizontal: ±(8 mm + 1 ppm x baseline length)
  
  Vertical: ±(15 mm + 1 ppm x baseline length)
  
  Note: IAPPK accuracies assume 1 m IMU-GNSS antenna offset 
• Heave Accuracy: 5 cm or 5% (whichever is greater) for periods of 20 s or less 

Additional Equipment required

Two GNSS antennas rigidly mounted so that they have more than 1 m ( greater than 2 m recommended) but less than 5 m  horizontal separation distance between them.

POS MV Elite

Sources/Usage: Public Domain. View Media Details

The POS MV Elite is the highest resolution system for marine survey applications available from the manufacturer at this time (July 2020).

Specifications

• Manufacturer -  Applanix  
• Model - POS MV V5 POS Computer System (PCS) with type 33 IMU
• Weight  - PCS 3.9 kg; IMU 4.5 kg
• Dimensions -
  
  PCS 19-inch rack mount chassis, 1U high (442 mm X 46 mm X 356 mm)
  
  IMU 229 mm X 315 mm X 196 mm
• Power Requirements - AC 120/230 V, 50/60 Hz, auto-switching 40 W

Operational Characteristics

Maximum real-time data output of 200 Hz over ethernet

Accuracy specifications with Inertially Aided Real-Time Kinematic (IARTK) corrections

• Roll, Pitch accuracy: 0.003° (1 sigma)
• Heading Accuracy: 0.015° (1 sigma) with 2 m antenna baseline, 0.008° (1 sigma) with 4 m baseline
• Positioning Accuracy:
  
  Horizontal: ±(8 mm + 1 ppm x baseline length)
  
  Vertical: ±(15 mm + 1 ppm x baseline length)
  
  Note: IAPPK accuracies assume 1 m IMU-GNSS antenna offset
• Heave Accuracy: 5 cm or 5% (whichever is greater) for periods of 14 s or less

Additional Equipment required

Two GNSS antennas rigidly mounted so that they have more than 1 m (greater than 2 m recommended) but less than 5 m  horizontal separation distance between them.

Dynamic inclinometer

Sources/Usage: Public Domain. View Media Details

The dynamic inclinometer allows tilt measurements relative to the gravity field (g) regardless of the dynamic loading being experienced. That is, horizontal accelerations are not included in the measurement, only that of gravity. Can be used on watercraft to measure attitude relative to earth normal.

Specifications

• Manufacturer: Signal Quest
• Model: SQ-GIX-0200
• Weight: 2lbs
• Dimensions: 2.7”x 2.5”x 1.2”
• Power Requirements: 9 – 36 VDC @ 40 mA
• Data rate up to 250 Hz
• Tilt accuracy to 0.5° dynamic or 0.1° static

Operational Characteristics

• Package is only meant to be splash-proof (i.e., for use on a personal watercraft)
• Output stream is sent via CAN bus data convention
• Range of values is from +90 to -90 degrees from vertical
• Rugged to 100 g of shock loading
• Data rates can be decimated to a more tolerable rate

Additional Equipment required

• Waterproof microcontroller, developed by PCMSC MarFac, to read the CAN bus stream and convert to a useable form of data such as RS232
• Power Source