Down Imaging vs. Side Imaging: Differences and Similarities

While many anglers believe one is “better” than the other, down imaging and side imaging are actually two different types of sonar to help you detect fish under the water.

As someone who has used both, let me break down exactly how each one works.

Last updated: January 7th, 2025

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What is Down Imaging? 

Down imaging is like having an underwater flashlight pointing straight beneath your boat. The transducer sends sonar waves directly downward, creating clear images of fish and structure in a cone-shaped area below you.

A majority of fish finders in the market use down imaging (sometimes labeled as “DownVu,” “DownScan,” or “DI”) because it’s cheaper and popular for targeting smaller species like bass and panfish.

Since it shows what’s directly under your boat, it’s also easier to interpret than other sonar types.

What is Side Imaging?

Side imaging scans the water horizontally on both sides of your boat, creating a wide search pattern that covers more area. It helps you quickly scan the water because you’re capable of looking in two places at once.

Side imaging fish finders aren’t always the best choice for locating smaller fish because most people use them with trolling motors which makes it easier to cruise by schools without noticing them.

In my experience, they really shine in shallow water environments like rivers and creeks, because you can effectively scan both shorelines at once.

Down Imaging vs Side Imaging

This difference might not seem like a big deal or a difference at all. However, I firmly believe that knowing how to read your fish finder correctly can increase your chances of success on the water.

Down Imaging: Pros and Cons

Pros

• Scanning Deep Waters: More useful for deeper waters since its vertical scanning provides clear images of fish and structure directly below your boat.
  
• Speed and Efficiency: Typically produces higher quality images when traveling at high speeds. If you’re trying to cover a lot of water in a short amount of time, down imaging is the way to go. 
  
• More Affordable: As someone who watches their fishing budget carefully, I appreciate that down imaging often costs less than other options (not always though), especially through GPS fish finder combos.

Cons

• Limited Coverage Area: The single transducer setup means you’ll only see what’s directly under your boat. This can also result in lower-quality images with less resolution. 
  
• More Time Searching: Even though the imaging works at higher speeds, you’ll need to drive over every spot you want to check. In other words, since it’s vertical images, you won’t get horizontal information like a side imaging fish finder, leading to the need to cover more water.
  
• Quality Concerns: Since down imaging is often marketed as the budget option compared to side imaging, some manufacturers may cut corners. This increases the chances of you purchasing a bad product and having to send it back. 
  

Side Imaging: Pros and Cons

Pros

• Wider Coverage: Using two transducers, side imaging lets you scan in both directions simultaneously, giving you a full view of what’s happening on each side of your boat.
  
• Complete Package: Side imaging units typically come as premium models that include down imaging capability as well. This means you can switch between views to get the most complete picture of your surroundings without missing anything.
  
• Better Image Quality: The dual transducer setup combined with slower boat speeds often results in clearer, more detailed images compared to down imaging.
  
• Shallow Water Excellence: I think side imaging is the best choice in shallow waters or rivers because it picks up a better reading since it can’t go as deep as down imaging scanners. In smaller rivers, you might even cover the entire width with a single pass.
  

Cons

• Higher Cost: Side imaging systems come at a premium price since they include both side and down imaging capabilities. While some units allow you to upgrade from down to side imaging later, the initial investment is typically higher.
  
• Limited Depth Performance: I find side imaging’s main drawback to be its reduced effectiveness in deeper water. It works best in shallow waters under 10 feet – beyond that, image quality can start to suffer.
  
• Speed Restrictions: These units require you to travel at a slower speed for developing proper images. This could be a good or bad thing.
  While this slower pace might help you spot things you’d otherwise miss, it does mean covering water takes more time. It all depends on the range of your model. 

Is One “Better” Than The Other?

Both of these fish finders have their purpose with pros and cons. They operate differently and I find that they work best when put together.

That’s the reason why I recommend buying a down imaging and side imaging combo if your budget allows. You’ll often see these marketed as “dual scan” or “triple threat” on Amazon by major brands like Garmin, Humminbird, and Lowrance HDS.

You’ll often see the term “Chirp” mentioned with both types. This refers to the 2D sonar technology that provides a continuous flow of data from the unit to help you spot fish.

Choosing the right technology really comes down to your fishing style:

• Shallow River Fishing: If you primarily fish shallow rivers, side imaging is your best bet. Down imaging will do you no good.
• Deep Water Fishing: If you’re the type who anchors in deeper spots and waits for fish to come to you, a down imaging unit will serve you well.
• Ice Fishing: Down imaging is the clear winner here. You need to see what’s directly below your fishing hole, and side imaging won’t function properly through ice anyway.

The best choice depends on where and how you plan to fish. For many anglers who fish various waters, a combo unit offering both technologies provides the most versatility.

Frequently Asked Questions

Final Thoughts 

By this point, you should clearly understand the differences and similarities between these two types of sonar. In reality, you could easily get by with either of these. Side imaging is an upgrade but it’s not necessarily “better.” 

Think of it more as, “in addition to.” Side imaging is beneficial because it provides you with more flexibility in terms of your imaging but that doesn’t make it “better.” 

It’s like comparing apples to oranges. I hope this squashes the down imaging vs. side imaging debate and helps shed a little light for you. Good luck and happy casting!