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TOPIC: Depth Grid Resolution

Depth Grid Resolution 8 years 3 weeks ago #10463

  • athtest800
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Hello!
I have a lowrance elite ti sonar.
When I import the sl2 to Reefmaster I get grid with ~1 meter canvas per measuring. Can I make smaller gaps of this grid?
Is it limitation of the sonar and how it is calculated?
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Depth Grid Resolution 8 years 3 weeks ago #10465

  • Matt
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This is a limitation of the Lowrance recording format, which only provides a resolution of approximately one metre.
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Depth Grid Resolution 8 years 3 weeks ago #10468

  • athtest800
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Thank you!
I found that "Bytes per sounding"increase resolution on the lowrance unit. Do you know if that decreases the distance between sampling?
Do you have any recommendation?
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Depth Grid Resolution 8 years 3 weeks ago #10469

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Bytes per sounding increases the sonar image resolution for each ping and has nothing to do with position resolution. Lowrance uses a position format that cannot provide a better resolution than you show in your image. In practice, this is unlikely to cause any issues when mapping since 1m is likely as good or better than the GPS accuracy in any case.
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Depth Grid Resolution 8 years 1 week ago #10567

  • athtest800
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Do you think that if I feed the ReefMaster Software with external (live) GPS data via Serial port, and depth data from NMEA (from the Elite Ti) I will get better resolution?
Is this solution? I ask because I do not have the NMEA cable right now in order to check depth data rate of the Lowrance.
Thank you.
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Depth Grid Resolution 8 years 6 days ago #10568

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Yes, this could give a higher positional resolution to the data points but it is very unlikely that this will result in a significantly better map. Firstly, your GPS positional accuracy would need to be significantly better than the 1m resolution you can already get from your Lowrance, so you'd need to running an RTK GPS system, and secondly there are many other factors during map making (cone angle, interpolation effects, grid resolution used during map generation etc) that would likely render any marginal improvement in the accuracy of individual data points rather moot.
Sidescan mosaics are slightly different, where precise position and heading can make a significant improvement but this wouldn't be possible using the method you suggest.
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Depth Grid Resolution 8 years 6 days ago #10571

  • athtest800
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Thank you for the reply.
I plan using an RTK GPS (20Hz). The depths will be shallow so I do not think the cone will be problem. Later I will compute the roll,pitch,yaw with an IMU so to calibrate the depth with the wave movement of the boat.
About your second answer, about improvement of mosaic, do you have some more info to look into? I am programmer with mapping and mathematics background so will be challenge for me. The last belongs to methods outside the ReefMaster features?
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Depth Grid Resolution 8 years 6 days ago #10572

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From a quick research in this forum I think that you talk about heading of the sonar in addition to the RTK position?
Is it true? My RTK GPS has also heading with dual antennas. Will ReefMaster work with accurate position and Heading for better sidescans? Will I feed them with the LiveData feature of the software?
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