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How are the depth layers in the Eco determined? Are they equally spaced?


1 comment

  • Official comment
    David Velasco

    The three depth layers in the Eco are NOT equally distributed over the entire water column.  In fact, as with any ADCP, they cannot be equally distributed due to sidelobe interference, which is a region near the surface where the acoustic pulses interfere with actual surface itself and therefore the data becomes unusable.

    To determine the default location for the three layers, the Eco first determines the maximum water level for the entire data set.  See the "What is the reference position for the three depth layers shown on the WebApp?" FAQ for more details.  The Eco's automated quality control algorithm then evaluates the quality of the acoustic data below this level, invalidating any data that does not pass quality control. Please see the paper "Development of a low cost, self-configuring ADCP and integrated deployment and recovery system”, D. Velasco, M. Jørgensen, A. Nesheim, S. Nylund, Proceedings of Global Oceans Virtual Conference, Oct. 2020" for details on the algorithm. One aspect that the algorithm must consider is the instrument's tilt. As tilt increases, the region near the surface that cannot be measured also increases, because each beam will have a different range to the surface. After all quality control measures are applied, the Eco then takes the usable profiling range for the beam with shortest range to the surface and divides this range into three depth layers.

    You may also wish to review the below FAQs on the Eco App for more information:

    • "How close to the bottom or top of the water column can I measure currents?"
    • "Why are some measurements periodically missing from some of the depth layers?"
    • "I see the depth layers are at a fixed depth, but my site has a large tidal range. How does that work?"
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