A Guide To Selecting Your Next Fishfinder / GPS Chartplotter

Sonar, or “Fish Finding” technology has made incredible advances over the past few years, and innovations keep coming at an escalating pace.

Not too long ago, it seemed like manufacturers were getting complacent with fishfinder technology; technological advances were slow and incremental and it felt as if fishermen were getting left behind. But over the past few years, these same manufacturers have grabbed our attention again with advancements like multi-touch screens, WiFi, picture-like images of the bottom, and even 3D and 360-degree sonar. Things have been changing so rapidly that it’s easy to become overwhelmed with all of the different features that are available on even the most basic of fishfinders and chartplotters available today.

Before you tackle the buying decision for your next electronics purchase, take a few moments to understand how this technology works and to get up to speed on the latest in marine electronics technology.

Understanding Fishfinder Technology


Sonar or fishfinder power is measured in watts RMS (root mean squared). Higher power means a better picture in deeper water, better visibility in dirty water, and a better ability to separate targets from the bottom. Most units have enough power for inshore/coastal applications, but serious deep water anglers may want to look for something that supports 1,000 watts or more. In the case of power, higher is always better, just be sure to use a compatible transducer that can maximize the power of your fishfinder.

Transducers and Frequency

Fishfinders utilize transducers to send out soundings and receive back echoes from whatever the waves bounced off of on their way to the bottom. These transducers can typically operate in different frequencies, depending on the depth in which you are using them.

Higher frequencies give the best detail, return the least noise on screen, and work best on a fast moving boat, but they don’t work as well in deep water. Lower frequencies penetrate the deepest, but do so in exchange for slightly less detail and a little more noise. If you’re a coastal or inland boater fishing in depths up to 200’, it’s likely you’ll choose higher frequencies of 200kHz, 455kHz, or 800kHz. Offshore blue water boaters are likely to get more use out of frequencies in the range of 80kHz to 50kHz.

But What About CHIRP?

While traditional sonar only utilizes a single frequency to send out sonar “waves”, CHIRP continuously sends a range of both low and high frequencies, and then interprets each frequency individually upon its return. Because CHIRP sonar receives a much wider array of information, the fishfinder is able to distinguish targets better, and provide a much higher resolution image with much more clarity than traditional sonar. This all ads up to a much better sonar experience, allowing anglers to actually distinguish individual baitfish and fish within a school like never before.

A fishfinder operating at high chirp. Note the clear definition of each individual fish represented as an arch.

Do I need Structurescan / Side Scanning / DownVu / SideVu / Side Imaging?

If you look at the various manufacturers units and feel a bit confused about whether you need StructureScan, DownVu, SideVu, or the like, then you’re not alone. Each manufacturer has developed their own marketing lingo to talk about the same exact set of features. When referring to these features, Navico (Simrad & Lowrance) uses the term StructureScan, referring to both down and side scanning, Garmin has coined the names DownVü and SideVü, Raymarine uses Downvision and Sidevision, and Humminbird calls this Side Imagine and Down Imaging.

Side Scanning and Down Scanning sonar enables you to see incredibly detailed, picture-like images of anything in the water below or to the side of your boat. This type of sonar utilizes a narrow beam at a much higher frequency to produce a low-distortion, super high quality image of both structure and fish beneath and to each side of your boat.

StructureScan showing a down imaging view of trees underwater.

What transducer do I need?

The transducer is an essential part of the sonar system and choosing the right one is an important decision. Most lower and mid-grade fishfinders come bundled with a transom-mount transducer that will be perfectly adequate for most lake and inshore applications. However, if you’re serious about getting the absolute best image from below your boat, you may want to consider upgrading to a thru-hull style transducer. Thru-hull transducers are install “through the hull”, meaning you’ll have to drill a hole in the bottom of your boat, but these types of transducers offer superior imagery.

For higher end units, the transducer is often sold separately. This is done so that the angler can make their own decision on the frequency of transducer, and the style of installation whether it be transom-mount, thru-hull, or in-hull.

The Navico TotalScan All-in-one transducer featuring Broadband, CHIRP, StructureScan HD and DownScan Imaging™

What Type of Unit Should You Buy?

Now that you have a basic understanding of fishfinding technology, you should feel more confident when looking at the various units available on the market. But before you make your decision, you need to understand the different types of units that are out there.

Standalone Fishfinders

Furuno FCV-588 standalone fishfinder

The standalone fishfinder only includes sonar capabilities and none of the extra features like GPS and Mapping. These units have a wide variety of applications from the small lake angler with no need for mapping, to the serious offshore fisherman who desires the best in fishfinding technology and wants a dedicated screen just for that.

For a standalone fishfinder on a budget, we recommend looking at the Lowrance Hook-7x. If you’re looking for one of the best consumer standalone fishfinders available today, check out the Furuno FCV588.

Fishfinders With Basic GPS Capabilities (No mapping)

Manufacturers have recently come out with fishfinder units that also have basic gps functions. Consumers often fall into a trap thinking that these cheaper units will do the same things as a more feature-rich chartplotter, but these basic GPS units lack the ability to display charts. Anglers can still enter waypoints and navigate between them, but they will not be able to see where the waypoint is in relationship to a map. While this is a welcome addition and a useful feature on what were once typically standalone fishfinders, do not fall into the trap of thinking these units will work as an aid to navigating your inland or coastal waterways.

In this category, one of the units we recommend is the Garmin Striker 7cv.

Garmin Striker 7CV Fishfinder with basic GPS capabilities

Chartplotter (GPS) / Fishfinder

Gone are the days where you needed to buy two separate units in order to have sonar and chartplotting capabilities. Today, the most common of the types of fishfinders you will see on the market today feature a combination of these functions. These units combine sonar capabilities alongside mapping/chart functionality in a single, often very affordable, standalone unit.

Lowrance Elite-5 Ti combination chartplotter / fishfinder

All of the combination units available today provide traditional sonar, most are now including advanced features like down imaging, and a select few are even including side scanning functionality. This all adds up to an incredible amount of technology packed into these units. But buyer beware, while these units pack a big punch, they are restrictive in that you cannot build an advanced network that will include features like sharing charts and data across multiple screens, or radar integrations. This is due to the fact that these units lack the ethernet port that is required to build the network.

Although all of these combination units feature some sort of mapping/chart solution, it’s important to know that all maps are not created equal. When looking at the various manufacturers, it can be easy to become confused with all the different terminology. Add the fact that most chartplotter/fishfinder units support 3rd party mapping solutions, and the waters just got even more muddy.

At the very least, your chart plotter should come with a base map. The exact features of the base map vary by manufacturer, but these maps are often not very useful for navigation purposes.

Garmin echoMAP CHIRP 94sv combination chartplotter / fishfinder

Beyond the base map, some units come with preloaded maps provided by the manufacturer. For Garmin they are called Bluechart, Simrad/Lowrance named them Insight, Raymarine calls them LightHouse charts, and the list goes on. In addition to manufacturer charts, there are various 3rd party charts from companies such as Navionics and C-Maps. Choosing a map is really just a matter of preference, so do your research and pick the best maps for you.

There are many units that fall into this category, but some of them that we recommend looking at are the Lowrance Elite-5 Ti, Garmin echoMAP CHIRP 94sv, Raymarine Dragonfly 7PRO, and the Furuno GP1870F.

Multifunction Networkable System

Moving a step up in price and functionality are the multifunction displays. These units typically offer all of the functionality of their lesser brethren, with the addition of full networkability, multiple transducer ports for more complex sonar needs, and much more. These devices are the foundation on which you can build a complex network that can include multiple screens sharing data and installations which require additional equipment such as radar.

Though there are many units in this category, some of the more popular ones are the Simrad NSS12 EVO3, Lowrance HDS-9 Gen3 / Lowrance HDS-7 Carbon, Garmin 7610xsv, Raymarine Axiom 12, and the Furuno NavNet TZT9.

Simrad NSS12 Evo3 Multifunction Display

The Hybrid

Simrad GO9 XSE – A hybrid charplotter / fishfinder with radar capabilities

To make things even more confusing, some manufacturers have started releasing chartplotter fishfinders with limited networkability. These are not able to fully network like a multifunction display would, however they are able to take advantage of some advanced functionality like radar and autopilot.

In this category, there is a clear winner in the Simrad GO9XSE from Navico. This unit packs a big punch with a multi-touch 9” screen, medium/high frequency CHIRP sonar, StructureScan HD imaging, Radar compatibility, Wifi, and the list goes on.

Glass Helms / Monitor Installations

Finally there are the biggest and baddest of them all. The latest in “Glass Helm” technology features large 16-24”+ touchscreen monitors that function similar to regular television sets. These are to be purchased as the platform on which to build an extremely complex control system for the biggest of center consoles and yachts. We won’t go into too much detail, but if you’ve got a big budget for electronics you can look into items like the Garmin 8624, which starts at $11,999.

Garmin 8624 Glass Helm Display

What Size Unit Should You Buy?

The simple piece of advice we can give here is to buy the biggest screen that you can afford. Today’s units typically come in 5”, 7”, 9” and 12” sizes. With the ability to split the screen and show multiple sonar and charts on almost all of these devices, it’s handy to have the bigger screen sizes so you aren’t squinting to see each part of the screen. So if you’re planning to use one of these for both sonar and gps, consider buying a unit with a screen size of at least 7”. If you can’t afford the larger 9” or 12” screens, you can also start with one smaller screen, say a 7” screen, and later on add another 7” screen to effectively double your screen real estate. Often times you can purchase two 7” screens for a marginally higher price than just purchasing a single 9” screen.

Other Technology To Consider

What is NMEA2000?

We briefly discussed the ability to network multifunction displays via ethernet, but there is another networking protocol that most units support called NMEA2000. N2K (NMEA2000 abbreviated) is a largely standardized protocol used to create a network of electronic devices on a boat. Manufacturers have come out with a wide array of instruments and sensors that meet the NMEA 2000 standard and can be connected directly to your N2K capable display. These instruments are all connected to one central cable, known as a backbone, which effectly creates a network where all of the devices can talk to each other. The effective result is that your one display unit can display information from other instruments, sensors, and even other sonar and chartplotter displays.

With this technology you can display your engine gauges directly on your N2K compatible chartplotter/fishfinder display, share waypoints across multiple chartplotters, send GPS information to your VHF radio for distress signals, and much more.


Most of the mid-to-high end units coming out today support some sort of WiFi out of the box. This is extremely exciting technology for gear heads like ourselves and it opens up a whole new world of features to boaters. With a unit like the smaller Simrad GO7XSE, you can connect an iPad to the Simrad via WiFi and actually view and control your chartplotter directly from the iPad! WiFi also enables you to do things like purchase charts, upgrade software, and migrate data.

Wrapping Up

We hope this article was helpful in educating you about your next fishfinder or chartplotter purchase. While we touched on a lot of features and technical information, we just scratched the surface on all of the amazing technology that is available today. Buying electronics for your boat is a large investment, and being educated about the technology that is available today will help you to confidently make your purchase.

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