NOAA Ship Fairweather 2015 SAT

Multibeam System: 
EM710

Executive Summary
A Kongsberg EM710 multibeam echosounder was installed on the NOAA Ship Fairweather by Bay Ship and Yacht Co. of Alameda, CA in December, 2014. This mapping sonar replaced a Reson 8160 and a Reson 7111.

The performance of the EM710 was evaluated during sea‐trials from 9 February to 13 February, 2015. The performance of this system as installed and integrated meets the manufacturer specification and is adequate to meet the intended charting mission. All modes of operation were tested between 50 and 500 meters.

This analysis and report follows the Office of Coast Survey Multibeam Sonar Test Procedures [1]. Section numbers of the test procedures are reference in the headings thus: (MSPT 1.1).

Significant Findings

  1. Relative to the internal noise of the system, the installation has low flow noise and imperceptible direct‐path propulsion noise. The radiated, bottom‐bounce propulsion noise is noticeable in shallow water, but is not speed dependent and can be minimized with shaft speed and pitch combinations.
  2. The swath width as a function of depth meets or exceeds specifications.
  3. The system bathymetry meets or exceeds specifications in all modes tested.

Recommendations

  1. We recommend the ship consider draft variation from typical fuel burn and launch‐load and both derive a nominal draft condition and determine how often, if at all, this draft value should be updated through the field season. The nominal draft condition should be updated in SIS and the HVF. Periodic updates to this draft value to account for loading condition, if warranted, should be made in the HVF alone.
  2. Absolute accuracy was not tested during these trials. We recommend comparisons of the EM710 bathymetric data with other systems.
  3. A latency value of 14 milliseconds was derived for the attitude and updated in the configuration. This should be retained and the post‐processed motion correction process should be modified as discussed in this report.
  4. The CARIS license enabling use of the Kongsberg SVC module should be used for all computers used to process data from this system.
  5. Typical survey configuration should be with dual swath, pitch and yaw stabilization on. The typical survey speed for Complete Coverage Surveys may be increased to 10 knots.
  6. Raw data should be carried over on conversion to allow the proper functioning of the Kongsberg SVC correction. This guidance may be revised for CARIS 9.0.
  7. An updated BsCorr file should be uploaded as soon as developed by HSTP to ensure the best possible backscatter.

AttachmentSize
FA EM710 Gondola Alignment Survey Report.pdf1009.35 KB
FA_EM710_acceptance.pdf4.95 MB