Fig. 11
From: Sounding out life in the deep using acoustic data from ships of opportunity
Another example of compromised quality data comparing unfiltered and filtered echograms with metrics of data quality. The 38 kHz data was collected by FV Isla Eden transiting from Mauritius to Heard Island and McDonald Islands in Southern Indian Ocean. (a) Displays calibrated and motion correction applied echogram before the application data processing filters outlined in Fig. 5. Panels (b,c) show SNR and ‘smoothed’ background noise level calculated after background noise removal filter used in the filtering stage. Note that the triangle wave error present in background noise level was smoothed for comparison purposes. For this transect, the error was not averaged to zero over the 1 km horizontal distance, possibly due to slow ping rate achieved. (d) Depicts percentage of data retained after the filtering process. (e) Filtered data before applying secondary corrections for sound speed and absorption variation.
