Analysis of bottom-track and compass error in a self-contained acoustic doppler diver navigation console
The Cobra-Tac (Teledyne RD Instruments) is a self-contained diver navigation system based on acoustic Doppler velocity log (DVL) technology that uses dead reckoning to compute displacements from a known starting point. The navigational accuracy of the system was evaluated using a series of field tests with known solutions. Initial test data had an obvious directional bias in the navigation measurements, with positional errors as large as 5% of the track length. An analysis of this error showed that the DVL speed measurements were extremely accurate and that most of the position error could be explained by heading-dependent compass error. Compass error versus heading curves were different depending on whether a given route was mapped in a clockwise or counterclockwise direction, and further testing indicated that this was due to a combination of local magnetic field anomalies at the test site and instrument tilt. A postprocessing correction procedure, based on a one-cycle compass error model, was derived that significantly improves Cobra-Tac position estimates. After correction, position errors were well within manufacturer specifications. Further tests using new firmware that permitted in situ underwater compass calibration gave position errors of less than 1% of the track length. This level of accuracy should be sufficient for a wide range of scientific applications. Collectively, the test results and analyses indicate that Cobra-Tac can give very accurate navigation results, but the accuracy depends strongly on compass calibration and diver skill with the system. © 2010 American Meteorological Society.
Duke Scholars
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Related Subject Headings
- Meteorology & Atmospheric Sciences
- 3708 Oceanography
- 3701 Atmospheric sciences
- 0911 Maritime Engineering
- 0405 Oceanography
- 0401 Atmospheric Sciences
Citation
Published In
DOI
ISSN
Publication Date
Volume
Issue
Start / End Page
Related Subject Headings
- Meteorology & Atmospheric Sciences
- 3708 Oceanography
- 3701 Atmospheric sciences
- 0911 Maritime Engineering
- 0405 Oceanography
- 0401 Atmospheric Sciences