Thursday, July 31, 2014

Low cost sidescan for eelgrass mapping?

We're trying to map eelgrass in shallow water.  This has been an instrument challenge for years (decades?) that has required experimentation.  Aerial methods are great, but costly.  Remote control aerial is something we're interested in, but we don't have the proper licensing yet.  Processing might still be a real hurdle with aerial photographs too.  So we're focusing on vessel-mounted systems that can be deployed rapidly with data collection tools that result in data that needs minimal processing, or at least a workflow that can be standardized and result in maps in a matter of a day or two.

Most recently we've been using a Biosonics DT-X on a small boat.  Vessel draft and maneuverability is still a concern in shallow waters that frequently have obstructions, especially rocks.  So now we're testing a jet ski, on loan from colleagues in Maine.  Our plan was to mount the Biosonics on that, but our trial run with the jet ski made us realize just how wet it is.  To use the Biosonics, we would have to do some pretty involved retrofitting to have the necessary ruggedness.  If the jet ski proves to be a reliable platform, we might put the effort into the retrofit since we like the almost non-existent processing required of the Biosonics data.  In the meantime, a colleague here at DMF, Mike Bednarski, showed me his Humminbird 698SI.  So we'll take that out and see what sort of eelgrass mapping we can do with it mounted on the jetski.

Here's the whole unit -- transducer, processing unit, and storage (SD card).

Color Palette
Here's an image from the Humminbird website.

We'll be out in a couple of weeks to see if we can image eelgrass and mooring scars in eelgrass.  Some folks at the USFWS have put together some great descriptions and details about how they use their Humminbird for habitat mapping here.

Thanks Mike!

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