Fish finder technology has improved dramatically over the past 15 years, giving rise to a wide range of types of fish finders that provide many different ways to see the underwater world.
But the availability of all this sonar technology can also make it hard for beginners to get an accurate overview of the different types of fish finders, and what they can be used for.
Explanation of Different Types of Fish Finders
Now let's take a closer look at each of the main fish finder types, to get a better understanding of what they are capable of.
However, most marine fish finders nowadays combine many of the above-mentioned sonar technologies into one unit, and it is rare to get a fish finder equipped with only one type of sonar.
2D Sonar
2D sonar is the oldest type of fish finding technology, and is therefore often called traditional sonar. 2D sonar uses a circular transducer that launches a sonar cone into the water that expands as it travels through the water.
While 2D sonar has lower resolution than other types of sonar, it does come with the advantage that it penetrates the water deeper than side imaging or down imaging, and is also the main type of sonar used by deep water anglers targeting water deeper than 150 feet deep.
Down Imaging Fish Finder
Similar to 2D sonar, a down imaging fish finder also works with a sonar beam shot directly into the water, but unlike 2D sonar, its sonar beam is very thin, and does not expand as it travels through the water.
Due to the narrow sonar beam, down imaging shows a narrow cross-section of the water and bottom directly below your boat, thus generating a very high level of accuracy.
Bottom photography is great when you're fishing above structure, as it allows you to see every detail in high definition, including any fish in the area.
Side Imaging Fish Finder
As the name suggests, a side imaging fish finder uses a transducer that fires two sonar cones sideways on each side of the boat.
As a result of this setup, side imaging can cover areas of water as large as 240 feet on each side of the boat.
As in bottom imaging, side imaging uses short wavelengths of 455, 800, or even 1200 kHz. These high frequencies are great for generating high-resolution images, but they don't penetrate deep water very well.
Side imaging is ideal for scanning large areas of a lake in order to find fish-holding structure, which is why it is also often referred to as structure scanning.
3D Fish Finder
The 3D Fish Finder uses a software algorithm to combine data from the side imaging transducer into a 3D image, making it easy to get a clear image of how fish relate to structure.
This is different from other types of fish finders, which generate a 2D image that then needs to be interpreted in order to extrapolate 3D information.
However, while the 3D fish finder certainly creates very nice images, it doesn't give you as many advantages as most people think, and in my opinion it doesn't really justify the extra cost. In general, I always recommend live sonar rather than 3D sonogram.
Castable Fish Finder
Castable fish finders are wireless fish finders that can be thrown from the shore, and float on top of the water, with their sonar scanning what's underneath them in the water.
In most cases, castable fish finders communicate via Bluetooth with a smartphone or tablet, and provide a cost-effective way for inshore anglers to take advantage of fish finder technology.
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