11/19/2014 — admin
The transducer impedances are similar to baseline measurements in 2012 and with those taken in 2013. Transducer conditions, based on these tests, are acceptable and there is no sign of degradation of the transducer arrays.
Noise levels for the EM710 remain unchanged and very low. Noise levels for the EM302 have increased at higher speeds though they remain low when the ship is stationary in the water, suggesting that the increase is associated with flow noise and/or the propulsion system.
The systems were successfully calibrated with a second confirmation calibration indicating that the results are acceptable. Angular offsets are small and very similar to those found in previous evaluations. The systems have been updated with the
new calibration results.
Both multibeam systems provide bathymetric measurements that are in agreement with the expected performances of the systems and that are consistent with previous examinations. There is no evidence of degradation of ancillary sensor performance since the previous accuracy tests.
Seabed imagery quality is good and is generally artifact free. There are residual inter-sector imbalances with the EM302 despite the signal balancing routines undertaken in 2012. The EM710 has slight signal imbalances, however, it is not currently possible to correct for this using the same mechanism that is used for the EM302 (though this would be possible in the latest release of SIS). In both cases, the residual offsets are easily corrected in commercial processing software.
At SOI request, verification testing of the Mammal Protection Mode functionality was undertaken. The source level reduction features are confirmed to work as expected. The “Soft Startup” works as expected with the EM302 but a software error affects the EM710 and a workaround procedure to ensure the correction functionality of the EM710 soft start must be followed. The workaround procedure is not particularly onerous and can be addressed through an upgrade to SIS and the firmware for the EM710.
As a whole, the two multibeam systems are in satisfactory working condition and we do not anticipate any problems with either system for the 2014 mapping season with the caveat that the increased noise levels will reduce the coverage efficiency of the EM302 sensor in deeper water.