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Thread: Laser or Sonar Bathymetric Data Gathering / Marine Surveying

  1. #1
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    Default Laser or Sonar Bathymetric Data Gathering / Marine Surveying

    Hi All,

    Anyone had any experience in marine surveying with laser or multibeam sonar?

    I would like to map the depth around a lake (0.5-20m<) onto a map and or 3D render.

    Seems to be a few open source software options to process the data but trying to find the best method to capture the depth + accurate GPS cords to do this, hardware wise.

    It's just a little hobby work so limited budget / non commercial / self funded.

    Chuck me a PM if you may be able to help or post details here!

    Thanks in advance.
    Regards,

    Aidan

  2. #2
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    Whatís wrong with the usual fish finder? The show the depth and map rather well. Those depths are reasonable. Garmin makes nice units. Not sure whatís out your way. Expect to pay couple grand. Maybe you can rent one.

    cheap way is lead and a rope. Mark off the rope. Drop in till on bottom. If you want to get fancy put a switch on the end on the lead weight that trips when you touch bottom. Use your phone for gps and plot.

  3. #3
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    Not sure fish finder will work on its own, GPS and sensor need to be positioned together and constantly stream data to a recorder.

    One may be part of the answer but from what I've read so far not all of it.

    Resolution of the sensor, GPS accuracy etc
    Regards,

    Aidan

  4. #4
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    I did a survey of Lake Erie. Well not all of it but a part and we used a towed sonar array. That was from nasa however. If you can rent on itís the right device.

    https://www.subseatechnologies.com/rentals/

    i expect it it will be expensive. If the lake is not huge.....rope and lead weight....

  5. #5
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    Former submariner here: if you're mapping the bottom of a lake you'll want to use sonar, not a laser. Far too many things will interfere with the laser!


    Sonar mapping of underwater contours is a solved problem with numerous commercial products to choose from depending on the level of detail you need. Towed sonar arrays are the cat's meow for this sort of thing, and as Marc mentioned you can probably rent this equipment. (Pay particular attention to side-scanning arrays, as they can *greatly* speed up the mapping process.)

    If you are on a budget and can't afford to rent commercial-grade mapping equipment you could do this yourself with off-the-shelf gear and some extra work. You'll likely need to record the GPS data and bottom contour data separately and then combine them after the fact using a time-stamp. But you would be amazed at the resolution provided by even a consumer grade depth finder / bottom plotter that can be purchased for around $400 from your local boating store. Pair that with a cheap GPS receiver that supports NMEA output and some free GPS logging software and you're off to the races.

    Adam

  6. #6
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    Thanks guys.

    I was thinking something along the lines of that, you can seem to get data records for NMEA its just getting the 2 right devices to get the data out.

    GPS is a tricky one as the "cheap" ones only seem to be accurate to 0-9m, which isn't of much use.

    Ill want to make a tow able thing with the sonar & GPS on to get it as accurate as possible.

    I could use a string and weight but im an IT guy, I want pretty 3D modules of the bottom mapped over google maps satellite image etc.

    Its mostly for fun so I just dont want to pay a lot for it, building the system is half the fun!

    Was hoping for some pointers of models of fish finders / GPS and general experience in the process.

    The lake is about a mile in circumference, nothing huge, 0.5-20m max depth, its an old quarry.
    Regards,

    Aidan

  7. #7
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    Smile

    Google is your friend. You want a depth finder that supports a NMEA interface.

    I found this unit in less than a minute that appears to do everything you need (GPS and depth finder combined - with NMEA output, data logging, and basic cartography software built-in) all in a single package for $550. I'm sure there are other options though.

    Adam

  8. #8
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    Thanks.

    I've found similar but think I will need to contact vendors.

    Having the features is easy, knowing they have the resolution desired is another.

    Just googling dosnt quite give the full picture.

    I'll make some calls and see what I can do.

    Thanks for the guidance.

    Yes it may have GPS but if it's +/-5m accuracy it's useless.
    Regards,

    Aidan

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