Down imaging vs Side imaging: Which one to use? (2024 Guide)

If you’re looking to buy a fish finder chances are you’re wondering whether it’s worth investing in a side imaging fish finder or a down imaging fish finder. It’s a tough call, especially if you’re new to the world of fish finders and don’t know all that much about them or even how to read them.

I never used to understand the different sonar technology in fish finders but once I got my head around down and side imaging technology, I could determine which one was worth having and why based on the fishing situations I usually find myself in.

Depending on your fishing style, the right fish finder can amplify your game by helping you see the sea (or really any fishing spot) from a whole new perspective.

Join me as I run through everything about down imaging vs side imaging technology so you have all the tools to make the right choice when buying your new fish finder.

What does down imaging sonar and side imaging sonar mean?

Before we really dig into the details about the side imaging and down imaging systems, let’s first get a bigger picture view of down imaging vs side imaging and what it really means.

It’s pretty much common sense as to how down imaging vs side imaging differ as it says it in their names.

Down imaging gives you vertical images of what is directly beneath (down) your boat and side imaging sonar gives you images of what is to the side, the left and right of your boat.

It’s quite simple when you think of down imaging vs side imaging like this but what does it mean on the water?

Down Imaging Fish Finders

Humminbird Down Imaging
Humminbird Down Imaging

Down imaging sonar is traditional sonar and it uses a single transducer to scan what is directly beneath your boat.

These down imaging scanners send out CHIRP sonar waves straight down to depths of up to 3000ft (model dependent) which are then reflected off any underwater objects they hit in the water column such as bait fish or underwater structures and the reflected sonar waves are then built into an image of what’s below you.

This is very useful information to have especially in deep waters as it allows you to know the exact depth, detect fish, plus see the bottom contours and depth changes.

Advantages Of Down Imaging Fishing Finders

  • Down imaging fish finders are great when fishing in deep water and/or using a deep water fishing style such as bottom fishing. This is because down imaging sonar shows you a vertical point of view using a razor thin beam allowing you to tailor your fishing tactics to depth, depth changes, and to target areas with more fish
  • Down imaging fish finders work at high speeds making them ideal for trolling for certain species that require more speed than others to bite, such as marlin or wahoo. This also helps you cover more water quickly so you can find the right depth or area you want to be fishing in without wasting any time
  • Down imaging units are also a lot more affordable than side imaging finders and therefore you’ll save a bunch of cash but opting for one

Disadvantages Of Down Imaging Sonar

  • Down imaging only scans what is directly under your boat and this is a lot less info than the 600ft of horizontal information that you’d get from a side imaging finder. You might be able to drive faster with down imaging but to cover an area of 600ft horizontally will take a lot of time
  • Most down imaging finders use standard sonar and a single transducer meaning you will have a lower quality image – this is dependent on the fish finder you buy though as some use multiple low and high frequency waves to give you a great image

When is down imaging worth it?

  • Down imaging is worth it when you are fishing for species that require you to be trolling at a high speed of 5 knots or over, such as wahoo, sailfish, tuna, marlin and most other pelagics too
  • Down imaging is also perfect for when you’re bottom fishing as it shows what it under your boat which is where your baits will be
  • If you’re fishing in deep water and looking for depth changes, down imaging is the best for that
  • Down imaging is also worth it when you’re on a budget, as it’s better to have down imaging than no imaging

When is down imaging not worth it?

  • When you are always shallow water fishing and/or at a low speed of under 5 knots
  • If you are never trolling or bottom fishing

Side Imaging Fish Finders

Humminbird Side Imaging
Humminbird Side Imaging

Side imaging sonar can use more than one transducer, depending on the model and side imaging transducers, or side imaging scanners, send out sonar waves to the left and right of your boat on a horizontal plane up to 300ft (model dependent) instead of straight down.

Like with a down imaging system, these sonar waves are then reflected by anything in the underwater marine environment from fish to rock piles and then created into a clearer picture for you to see.


Side imaging is very helpful for finding fish as you can see clear pictures of what is 300ft on either side of you allowing you to effectively cover a lot of water very quickly.

Advantages of Side Imaging Fish Finders

  • Side imaging fish finders are capable of showing you a larger proportional range of what is under the water up to 300ft on either side of your vessel. This means you are scanning a lot more water with every step you take than only knowing what is under your boat, which makes fish finding a lot more efficient
  • Side Imaging fish finders almost always come with down imaging, so you can choose to use either one when you want to depending on where and how you’re fishing 
  • Side imaging works very well at a slower speed and in shallow water such as shallow bays and shallow rivers allowing you to see almost what’s under water in an entire river from side to side, for example
  • A side imaging fish finder usually shows better image quality as they use high frequency waves that pick up a lot of detail

Disadvantages of Side Imaging Sonar

  • A side imaging fish finder will only give you a clear image when you are fishing or cruising at a slow speed of under 5 knots. This means it’s useless when you’re trolling at high speeds for the species already mentioned
  • Side imaging does not show you what is under your boat as it misses this as part of it’s scan meaning you won’t see any structure, fish, or depth changes that are directly under you vessel
  • Side imaging only works in shallow water as when it’s too deep, the sonar unit can not read the bottom
  • A side imaging fish finder is a lot more expensive than a down imaging fish finder
  • You will need to drive in a quite a straight line to be able to get clear images with side imaging

When is side imaging worth it?

  • When you fish in shallow water and want to scan a large area to find and catch fish quickly
  • When you want to have down imaging and side imaging at your fingertips as side imaging fish finders almost always come with down imaging too
  • When fishing at low speeds and want a better point of view to help you find fish
  • When you want to see detailed pictures of structure and how fish lie around them

When is side imaging not worth it?

  • If you tend to go bottom fishing or trolling at speeds of 5 knots
  • When you are fishing in deep water over 50 feet most of the time
  • When your budget won’t allow for it
  • When all you want to see what’s directly under your boat and not to the side
  • If you need to travel at speed want to see a sonar image at the same time


Lowrance Overlay Display
Lowrance Overlay Display

Can you get down imaging and side imaging?

Yes, as I mentioned above, most side imaging fish finders come with both sonar types for fish finding which allows you to switch between each sonar type depending on your fishing situation.

This is incredibly useful as it means you can see what you want when you want it and it guarantees to enhance your fishing experience as you will literally be able to see everything.

Can you see fish on down imaging?

Yes you can see anything that is below your boat with down imaging whether it’s a single big fish, a shoal of small fish, underwater structures that hold fish, and even underwater vegetation too.

Can you use side imaging sonar to pick up on structure?

As long as you’re in shallow water, side imaging will pick up on any structure on either side of your boat as long as it’s within the sonar range which is usually around 300 feet.

You’ll need to learn how to use the side imaging settings to see structure in perfect detail though as one you spot structure at maximum range you can hone it on it by changing the range and frequencies to get a better look at it and even see if there are fish holding on the structure too.

Can you use down imaging and/or side on a trolling motor?

Trolling Rods

You can add either down imaging and side imaging transducer to trolling motors but it’s best just to stick with down imaging on a trolling motor and here is why.

A down imaging transducer only scans straight down.

When you use a trolling motor, you’re going to be turning it left and right and this will not affect the down scan from down imaging as it still points vertically regardless of how you turn your trolling motor.

Scan Direction

A side imaging transducer scans left and right, now imagine what happens to the sonar beam when you turn your trolling motor, it’s going to move and end up giving you a very distorted image.

When you turn the trolling motor, the transducer will also turn and it will start picking up parts of your vessel when turned one way or the other, and will not be allowed to pick up reflections properly either.

So, with a trolling motor, stitch with down imaging and mount the side imaging transducer to the bottom of your vessel’s hull where it’s meant to go.

Is down imaging or side imaging better for kayak fishing?

Most kayak anglers struggle with side imaging as paddling in a straight line isn’t so easy on a kayak which may give you a distorted picture to work with instead of a clear one.

This issue isn’t something you have to worry about with down imaging, as no matter how straight you drive your kayak, it will give you a clear image.


That being said, it depends on your kayak angling setup. If you have a pedal powered kayak with a rudder you’ll be able to keep a straight course, and the same goes if you use a trolling motor.

Since kayak fishing takes place in shallower waters most of the time and you go at slow speeds, I’d suggest that side imaging would be best, as you’ll be able see an image of a much larger area, but only if you can maintain a straight course with ease.

Down Imaging vs Side Imaging – Which is best?

In all honesty, choosing between down vs side imaging actually comes down to one thing, budget, as you’ll get down imaging with a side imaging fish finder.

If you can afford it, it’s always better to be able to see what’s under the water beneath and to either side of your vessel whenever you like.

This way you can fish at high speeds and in deep water and see everything you need to at lower speeds and in shallow areas too.

Thanks very much for reading my article, I hope you enjoyed it and can now make a confident decision on the fish finder you should buy.

Please share this with your fishing friends too as picking the right fish finder can make or break a day on the water, and we all want good ones of those.

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