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TOPIC: E1 and E2 algorithms/corrections

E1 and E2 algorithms/corrections 2 months 1 week ago #12581

  • Ignacio Pereyra
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Hi!
I did a whole bathymetry of a reservoir with a Lowrance single beam echosounder HDS 7. The depths vary between 2m and 60m approximately.

When I try to map values of E1 and E2 in reef, I notice I high dependency on depths. Which brings me to the question if this values should be corrected, and how.

From what I saw in the forum and software manual, this values are unitless and highly dependant on weather/frequency/device.
My question is then, if there is a way to traduce them to power units (ex. W dB), any coefficient that may relate them, or how is the algorithm itself to calculate E1 and E2.
My first thought is to apply the sonar equation (Hamilton 1999, Kloser 2001, Buscombe 2014), to try to consider transmission losses and aperture of beam. Maybe this will improve the results.
Or does the software do any kind of correction already?

I have have 25 sediment samples with tested density and grain size distribution, which will be really interesting to correlate with this parameters.

Any help/info will be much appreciated!
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E1 and E2 algorithms/corrections 2 months 1 week ago #12582

  • Matt
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Hi,
Good question.
All units correct returns for depth to some extent, either through TVG or post processing, otherwise the intensity drop off is so great that there would be little left to display at higher depths. The issue is how they are corrected, and by how much.
It is true that hardness values show a strong correlation to depth for many units/transducers, and we did originally try correcting for this using various methods (including the the sonar equation that you mentioned), and also (in early beta versions) a user configurable depth compensation function.
The truth is that since consumer sonar units vary so much in how much dpeth is compensated, and cannot be calibrated, it wasn't possible to come up with a satisfactory solution to this.
It's definitely something that might be worth looking at again, and your data sounds very interesting - I'd be keen to see if if you can share (via This email address is being protected from spambots. You need JavaScript enabled to view it. ).
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E1 and E2 algorithms/corrections 3 weeks 7 hours ago #12656

  • Benji
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I'd be very interested - perhaps an advanced tuning option for the algorithm with depth windows e.g we could add a list of preferred gains 0-5M=1 5-10m=1.2 10-20=1.5 20-50=2.0 . even better if we could tell the algorithm known points in our data to say 'this is rubble, that is sand, that is mud' and have the algorithm calculate gains based upon our own units recordings (assuming all our recordings come from the same unit) I get it's a bit "hand wavy" but would be a brilliant addition
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