Spotting thermoclines with Humminbird Side Imaging

  • jhalfen
    Posts: 4179
    August 18, 2009 at 9:35 pm #1294853

    Some of the questions I receive on a regular basis have to do with the performance of Humminbird’s traditional, down-looking sonar. How well does it spot fish? How sensitive is it? How does it compare with other down-looking sonars on the market?

    As we all know, a picture is worth a thousand words. Here’s a picture that, I think, speaks directly to the questions about Humminbird’s down-looking sonar. This is the thermocline in one of my local lakes, set up at about 24 feet over 40-45 feet of water.

    As you probably know, the thermocline is that portion of the water column where temperature changes rapidly, with warmer water above and cooler water below. The densities of water above and below the thermocline are distinct (less dense above, more dense below), and it is this difference in water density that is identified by sonar.

    Not only will Humminbird’s down-looking sonar spot fish and structure, but it will also pick out differences in the density of water below the transducer…and that’s plenty sensitive, as far as I’m concerned!

    bigcrappie
    Blaine
    Posts: 4296
    August 18, 2009 at 9:39 pm #798416

    Where are the fish in a down looking shot? Or do you have one looking down with fish?

    jhalfen
    Posts: 4179
    August 18, 2009 at 9:43 pm #798418

    Now here’s what surprised me….the thermocline is also clearly identified by Humminbird’s Side Imaging sonar, and not only by the down-looking sonar returns.

    You can see the thermocline as a change in color of the water column, within that dark stripe running down the middle of the side imaging view. The upper portion of the water column (closer to the center) is darker than lower portion; that change in color corresponds to a change in the density of the water. The junction of those two colors is the thermocline (marked with red lines in the second image; cursor between the two pics for help in identifying it).

    Humminbird’s industry-leading Side Imaging technology spots structure and fish….and thermoclines as well. And for mid-summer suspended fish, finding that thermocline can make all the difference in the world.

    jhalfen
    Posts: 4179
    August 18, 2009 at 9:55 pm #798419

    Quote:

    Where are the fish in a down looking shot? Or do you have one looking down with fish?

    My 1197 spots fish without any trouble….in fact, that’s so routine that I had to dig just a bit to find a down-looking screen capture with some fish on it.

    Here’s one of a group of walleyes that I was spinner fishing in 25+ fow. They show up just like they’re supposed to on the down-looking view, and they even appear in the Side Imaging view….look for the white returns just above the bottom (marked by the red arrow).

    KirtH
    Lakeville
    Posts: 4063
    August 19, 2009 at 1:42 am #798476

    whittsend
    Posts: 2389
    August 19, 2009 at 2:15 pm #798586

    Jason –

    What sort of settings was the unit on? Mostly factory default stuff, or did you have to tweak anything? TVG on/off, sensitivity, etc??

    Finding the thermocline can be huge, especially if you have the trollers bible and/or know how deep your cranks are running…

    Thanks, sweet post!

    Mike

    jhalfen
    Posts: 4179
    August 19, 2009 at 6:17 pm #798676

    Mike, I’m still running an older software version on the 1197….I’ve updated my 997 but keep forgetting to do the 1197.

    The only thing of any consequence that I noticed in my settings is that I’m running down-looking sensitivity of 12. I collected those images at 5-6 mph, so there’s no need to creep around to find the thermocline.

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