12/07/2017 — admin
We installed four Kongsberg EM2040 multibeam echo sounders, one on each of Fairweather’s hydrographic survey launches during the spring of 2017 in Newport, OR. We accomplished the test and qualification of these systems on Puget Sound from May 22 through May 26. Conditions were generally agreeable for testing with some wind driven chop potentially affecting a limited set of noise tests. All systems were successfully integrated and measured performance was in compliance with vendor specifications and suitable for conducting NOAA hydrographic surveys.
Significant Findings and Recommendations:
- Four systems were installed and integrated according to HSTB recommendations and performed as expected.
- Sounding quality and object detection of these multibeams is significantly higher inside 65° from nadir. We recommend limiting the operational swath to 65° in most cases.
- The Fairweather hydrographic launches appear to have a relatively high noise floor dominated by bottom-bounce radiated noise from the propulsion.
- The acceptance testing schedule was compressed so the ship could begin a delayed field season. The schedule left limited time for processing and analysis on-site.
- The Shilshole reference surface, while valuable for its historical data, can have significant freshwater input from the Ballard locks and thereby experience oceanographic variability that is not ideal for calibration work.
- We have established a series of areas for future calibration and testing in Puget Sound.
- We recommend entering a 7 millisecond value for motion time delay into SIS for the Fairweather EM2040s.