Watson Compass

Watson Industries, Inc., Eau Claire, Wisconsin, USA

The Watson compass is a high precision reference system that was developed to overcome difficulties in obtaining headings when measuring vector data in areas where there exists potential for contamination of direction data. An example of such contamination occurs in the high Arctic where there is a small horizontal component to the earth's magnetic field. The compasses in commercially available current meters are useless in this case. The weak horizontal field also increases the potential for contamination of direction measurements by magnetic mooring hardware. The compass (SHR-360) is manufactured by Watson Industries, Inc.

In Ottawa, Natural Resources Canada Geomagnetic Laboratory tested the performance of an Acoustic Doppler Current Profiler (ADCP) compass against that of the Watson compass. The test simulated a field deployment in the Arctic.

The extent to which tilt inaccuracies impact on heading are not completely reflected in these results since tilts were held constant. Tilts are not constant when the instruments are used in the field.

SUBS unit

The compass is the metal cyclinder at the rear of the SUBS unit.

The Watson compass combines a high precision 3-axis fluxgate compass with precision pitch and roll sensors to resolve the magnetic field vector in order to determine direction. More detailed information can be found at the Watson Industries, Inc. web site in the manual for Strapdown Heading Reference compass.

In the field the compass was used with an ADCP to record velocities over an 80 m depth in Barrow Strait. The Watson compass measured the orientation of the ADCP relative to the magnetic pole. Both the compass and the ADCP were housed in a SUBS A2 buoyancy module.

Related Publications

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  • Hamilton, J. M. 2001. "Accurate Ocean Current Direction Measurements Near the Magnetic Poles"
  • Hamilton, J. M. 2004. "Accurate Ocean Current Direction Measurements from Instrumented Arctic Moorings"