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Deployment ru29-20200908T1623
Pilot Notes
UPGRADE FW Yes, this is a know issue. It caused me some grief recently, I only identified and fixed this bug just before Christmas. The anomalies in the pulse compressed echogram originates from a normalization bug in the processing. The normalization shift was not accounted for after the convolution, hence the steps in ~6dB corresponding to the normalization bit shift. We aim to release a new firmware version in January The good news is that this can be corrected since the complete echogram profile shall be shifted. It should work well to use the noise level in each profile as a measure of which shift that should be applied to that specific profile. I can send you some Matlab code later today that shows how this can be done. Regards, Sven Something to ponder… Looking at David’s cool echogram animation, I noticed that in many bursts there were vertical lines of lower (blue) or higher (yellow) EA than the background intensity. I was processing one cast – a ~ 500 m downcast on 23 Sept – for instance, running it through a computation to calculate exact pressure at each range based on tilt and beam angle – and noticed the same jumps, and their effect on trying to evaluate the data, see attached image. This is one downward profile, x axis is depth, y is echo amplitude, about 5800 pts (8 pings/burst x 4 sec / burst * 49 minutes). The three plots show mean EA at distance of ~ 3, 15, and 27 m range from xducer. I immediately didn’t like the multimodal nature – but now that I see animation, it seems like these are the result of those ‘vertical stripes’ – and that they occur in multiples of ~6 db, and in clusters in time/depth. The variability seems to track, it appears to be an offset. If anyone understands what might cause this, it would be great to think that we might correct to a standard ‘base level , or worst case remove outliers – can we assume the most populated level is the ‘correct’ one? But don’t want to do that without understanding the cause.
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