Specialty Devices Inc.

Hydrographic Survey Systems

Motion Reference Unit

Motion Reference Unit

The MRU uses 3 axis accelerometers, 3 axis gyros and 3 axis magnetic sensors integrated with dual embedded micro-processors to produce accurate pitch, roll and heave information in an industry stand- ard format. The MRU 333GI adds an internal GPS receiver and integrates GPS position with heading and speed to correct acceleration for heading changes. This improves settling following turns and removes errors in heave due to heading changes. A built in true north world magnetic map is used to produce a true north output. A “learning” software routine adjusts the MRU series to the boat characteristics to further im- prove overall accuracy.

Pitch – Roll – Heave
  • Single Beam Surveying
  • Multi-beam Surveying
  • Motion Stabilization
  • USBL Navigation
  • Hull Mounted ADCP
Pitch – Roll – Heave
  • GPS Aided—Course Changes
  • Single Beam Surveying
  • Multi-beam Surveying
  • USBL Navigation
  • ADCP Stabilization
Pitch – Roll – Heave
  • ROV Attitude
  • Diver Tracking Systems
  • Under-water Construction
  • Dredging Operations
  • Directional Drilling
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Options

Pitch – Roll – Heave
  • Single Beam Surveying
  • Multi-beam Surveying
  • Motion Stabilization
  • USBL Navigation
  • Hull Mounted ADCP
Pitch – Roll – Heave
  • GPS Aided—Course Changes
  • Single Beam Surveying
  • Multi-beam Surveying
  • USBL Navigation
  • ADCP Stabilization
Pitch – Roll – Heave
  • ROV Attitude
  • Diver Tracking Systems
  • Under-water Construction
  • Dredging Operations
  • Directional Drilling

MRU Mechanical Specs

Material T6061 T6 Anodized Marine AL
Diameter 7.6cm (3in.)
Length 25.5cm (10in.)
Weight 1.1kg. (2.5lbs.)
Depth Rating (MRU333) 450m (1500ft.) or 1800m (6000ft.) optional

MRU Performance Specs

PitchRollHeading ResolutionDegrees AccuracyDegreesStatic RangeDegrees RepeatabilityDegrees
Pitch 0.02 0.2 +/-180 0.05
Roll 0.02 0.2 +/-180 0.05
Heading 0.10 0.3 360 0.10
Update Rate All Parameters 30 per second
Heave HeaveAmplitudeAccuracy MaximumUpdate RateSamples/Sec. RangeMeters Drift(T=10s)
MRU333 5cm 0-10 sec.+/-5% 30 5 <5cm(uncorrected)

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Motion Reference Unit (MRU)