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Eco (bin) cell sizes during sampling and in webapp


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    Lila Johnson

    Hi Cynthia,

    Sorry for the delay in getting back to you. I understand your confusion with the bin sizes, hopefully this can help clarify. 

    The stated depths below the surface or above the Eco represent the center of the depth layer, not the beginning / end of it. So, for the example of the demo data, the three bins that are automatically created are centered at 7.1m, 8.6m and 10m depth; or, if you prefer to look at it another way, they are centered at 1.8m above the Eco, 3.3m above the Eco, and 4.8m above the Eco. 

    There will always be a bit of data loss close to the transducers of the Eco (the blanking distance, stemming from the time required for the transducers to stop vibrating and start listening for a returned signal) and closer to the surface (from lack of a strong return signal, sidelobe interference, etc). So, even though it may appear as though the depth layers are different sizes, in this particular example each "true" layer will be approximately 1.5m. The easiest way to figure this out would be to look at the differences between the centered depths-- i.e. 8.6m - 7.1m = 1.5m, even though that's technically measuring from the center of one cell to the center of the next cell. However, this bin size will vary with each deployment and with each time you wish to process the data using different depth layers, as will the amount of data lost near the surface. 

    To achieve this, the Eco does sample in smaller 0.5m cells, but the processing to generate the data for each of the three output layers isn't as simple as taking e.g. three 0.5m bins and averaging them. The same goes for changing the depth layers; the Eco will process the raw data differently to output new numbers.

    The Eco does use information on pressure to determine where the three equal layers should be and also references the maximum depth it experiences throughout the deployment based on pressure.

    In theory you would be able to export different depth layers at a higher resolution, but this would take a lot of time and processing at which point an Aquadopp Profiler would be more suitable for your application. Hope this helps!

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