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GPS & Basic Sonar Fish Finders: Our Buying Guide

Fishfinders come in various layouts and sizes and can include a wide range of both sonar and navigation features. Needless to say, each and every additional feature in a fish finder, whether it’s GPS or sonar-related, will increase its price.

Now, if you’re on a budget, or you don’t really want to spend an extra buck for a Side Imaging, Down Imaging or CHIRP fish finder, you can still get a pretty decent unit, which includes standard sonar, and a more or less extensive array of navigation features. A unit such as this can still get the job done, pointing out where the fish are, and of course, providing more or less information regarding your positioning, route, points of interest etc.

Nonetheless, there are several aspects to be aware of, if you opt for a unit with only standard sonar and GPS. So, especially if you haven’t used a fishing sonar before, here are a few pointers on how it works.

What Is Standard Sonar and How Does It Work?

First of all, your fish finder includes two main components: the transmitter (which is the operational unit, the monitor, or the head unit) and the transducer (which is the device that goes into the water, typically mounted on the transom of the boat). The head unit sends an electrical impulse to the transducer, and the transducer converts it into a sound wave and releases it into the water. When the sound wave hits a piece of structure, a fish or the bottom, it will be reflected back as an echo. The transducer picks up the echo, sends it back to the head unit, which interprets the data, materializes it on screen, and you get the information of the bottom, fish, structure and basically what’s under the boat.

The sonar beam emitted by the transducer has the shape of a cone and is typically directed to the water column directly under the transducer. The opening of the cone may vary depending on the transducer model, the frequency and the power of the pulse. In general, the more advanced the head unit of a fish finder, the more frequencies it can work it. But evidently, in order to operate at a certain frequency, a fish finder requires the appropriate transducer that can support that particular frequency.

Sonar and GPS in Split Screen

The most common frequencies that standard sonar fish finders use, are 50 kHz, 83 kHz, and 200 kHz. The middle range may vary, but in general, it’s 83 kHz. The lower, 50 kHz frequency is meant for deep water scanning, and fish finders with this type of transducer typically can scan depths of minimum 1200 ft (365 m), and up to 3000 ft (914 m), depending on power output. The higher, 200 kHz frequency, offers more detail, and typically supports narrower sonar cone beams, usually between 10°-20° depending on the transducer. Also, this frequency is meant for shallow water use, for up to 600 ft (183 m). Finally, the 83 kHz frequency is for mid-range use, for depths up to 1200 ft (365 m), and the angle of the beam may vary between 35° and 60°.

As you set your boat in motion, for most fish finders, the sonar image scrolls from right to left, becoming a record of the echoes picked up by the transducer. In standard sonar mode, fish usually appear as arches, or lines, while baitfish appear like bigger concentrations of noise. Vegetation typically appears as a sequence of irregular, continuous shapes, reaching from the bottom towards the surface. There are certain fish finders that can display the bottom in different colors, depending on its structure and hardness. For example, the Furuno GP1870F can distinguish between rock, gravel, sand or mud, due to its Bottom Discrimination function. The top line, i.e. the water surface, can appear very pixelated sometimes, as the transducer may pick up the turbulence generated by the boat’s motor.

Now, there are other types of sonar technology, such as CHIRP, side view sonar, or down view sonar. These offer better imaging than standard sonar, but nonetheless, they’re more expensive.

Choosing Your GPS / Sonar Combo

One of the main indicators of the price, value, and quality of a fish finder & GPS combo, is the size of the head unit, or the display. Usually, the larger this is, the more expensive and more capable the unit is. However, you may not need all the fancy features in a larger model. And since all units in this category feature just standard sonar, it goes without saying that the most extra features and capabilities of a larger unit are navigation oriented.

In terms of frequency, many units offer dual frequency sonar. However, not all of them are capable of 50 kHz frequency, for deep water fishing. Therefore, if you’re an offshore angler, and you might want some power with your depth finder, it’s best to opt for a unit that supports this frequency, and of course, includes the transducer for it.

If you don’t really fish offshore, chances are you may not need a unit with that depth capability. Thus, opting for a fish finder with 200/83 kHz, or something similar should do just fine. Evidently, if a GPS / fish finder combo covers the whole spectrum of frequencies, and can support various types of transducers, its price should be a little bit higher.

There are several fishfinding features that some of these units offer, which aren’t necessarily reflected by their final price. Most of them have a function that displays the fish arches as fish symbols, providing details about their size and depth. For Lowrance, this function is called Fish ID, for Humminbird is called Selective FishID+, while Furuno calls it Accu-Fish. Of course, for each brand, the function has slight differences.

Various fish finders that offer only basic sonar, also offer the circular flasher view. This is a sonar function which many anglers prefer for ice fishing or stationary fishing. In case you’ve used such a unit with this function before, and you’re familiar with it, it’s not a bad idea to opt for a fish finder which also has it.

On the other hand, there are functions offered only by the more advanced units. Two of them are sonar recording and temperature graph. The first one, as terminology suggests, allows you to record sonar, to review later, or import on an SD card to use on your computer. The second one displays the temperature fluctuations from a spot to another, data which may be quite valuable when fishing for certain fish. These functions, although pretty useful, they’re not really necessary, therefore it’s up to you if you would like to have them or not.

When it comes to navigation features and capabilities, there are several aspects to consider. First, if you really need a decent navigation tool, it’s a good idea to opt for a unit with a higher number of GPS channels. These provide superior sensitivity, positioning, and accuracy. GPS augmentation via WAAS or SBAS systems is a plus.

Next on the list is mapping. Each unit comes with a built-in, more or less advanced chart package. You will find units which come with only a “basemap” pack, which provides basic detail for navigation, but sufficient enough for an optimal navigation setting. Evidently, a unit with only a basemap chart package will be cheaper. Some units, on the other hand, are compatible with various, more advanced charts, such as Navionics Platinum+, C-MAP etc. Better charts are usually available on micro SD platforms, which can be purchased additionally. But for certain units, an SD card with superior charts may be included. This being said, it’s never a bad idea to opt for a unit that’s compatible with at least a few chart packs. Thus, even if the unit comes with only a base map pack, you’ll always have the possibility to upgrade.

Medium range and above fish finder & GPS combos, usually beginning with the 7″ display units, typically include navigation functions such as waypoints, routes and tracks. Waypoints give you the possibility to mark on your maps your favorite fishing spots, or any other points of interests. The routes function allows you to connect waypoints and set a course for better navigation. Some units also have route optimization functions, pointing out which are the safest routes connecting several waypoints. The track function allows you to record your course, in a breadcrumb (point by point) manner, for later use of view.

Nonetheless, if you’re going for one of the most advanced units, you should probably look for one that has at least a few functions such as weather and tide information, radar (or at least to be radar capable), AIS, NMEA2000 connectivity, autopilot functions etc.

Other Aspects to Consider

Transducer Availability

Before purchasing a fish finder of any kind, you should know that not all units come with a transducer. That’s why you must look carefully for the product you choose. It pretty much sucks to get the unit, and realize you have to go throughout the whole trouble of ordering a transducer as well, in order to be able to use it as a fish finder. Most of the units reviewed here though, do come with a transducer.

Also, the length of the transducer’s cable may be a good idea to check. Most come with 19 feet (6 m) of cable, but there are differences. This length should be enough for most bass boats, but in case you own a bigger boat, opting for a cable extension as you order the unit, may turn out to be a good idea.

Your Type of Boat

Most sonar and GPS combos come with a standard transducer to install on the boat’s transom. Now, depending on your boat, you may or may not be able to install such a transducer. Also, not all units may be appropriate for just any type of boat. For example, and expensive unit such as the Humminbird ION 10, may not exactly be the best choice for a kayak.


As I mentioned above, the size of a fish finder / chart plotter is an indicator of its price, usually the bigger, the more expensive. The bigger the screen, the more information can provide at once. But this is not the only aspect why size matters here. For example, you may want to install your unit directly into the dashboard of your boat.

SD Card Slot(s)

If a unit has an SD card slot, that’s quite a plus, because it most definitely accepts better chart packages, or you can use a blank SD card in order to save your waypoints, tracks, sonar etc. Some units feature two SD card slots, which is great, as you can use one for your charts, and one for saving data, without having to swap cards all the time.

Upgrade Possibilities

If a unit has an SD card slot, its map database can probably be upgraded. However, when it comes to upgrading, that’s not all you should be looking for. First of all, it is best to go with a unit that has upgradable software.

A Few Recommendations…

Under $200
Lowrance HOOK2-4x Bullet

In December 2017 Lowrance has released a new series of HOOK units, the HOOK2 series. Therefore, the Lowrance HOOK2-4x Bullet is one of the newest units for 2018. It’s actually a unit that aims to eliminate any unnecessary features in a simple fish finder, offering a single-beam broadband wide-angle sonar and a basic GPS plotter. The sonar can reach depths up to 500 feet (152 m), which can suffice for both in-land and off-shore fishing. The Bullet-type transducer is included with the unit. The GPS plotter, although it doesn’t use any charts, it allows you to mark waypoints for the best fishing spots with coordinates, suggestive icons, etc… Read Full Review.

HELIX 5 Fish Finder and GPS Combo - Humminbird$200 – $300
Humminbird HELIX 5 CHIRP GPS G2

The Humminbird HELIX 5 CHIRP GPS G2 is a re-designed HELIX 5 Sonar GPS. As its name suggests, it’s a unit that offers CHIRP sonar, featuring dual-frequency capabilities. It comes with the XNT 9 20 T transom transducer, which allows the system to use High CHIRP (175-225 kHz) and Med CHIRP (75-95 kHz). It has the Humminbird precision GPS, and in terms of charts it has the Humminbird UniMap, or the upgraded Humminbird Basemap. As opposed to the older unit, this one is also AutoChart Live capable… Read Full Review.

echoMAP 50s GPS Fish Finder from Garmin$450 – $600
Garmin echoMAP GPS 50s

Although this is also a 5″ display GPS and fish finder, its display has a different pixel matrix than the HELIX 5 GPS, 480H x 640V, with a vertical layout. It also provides dual frequency sonar, 200/77 kHz, and has a maximum depth capability of 1900 ft. Two of the plus features that this unit has over others, are dual SD card slot, and wireless connectivity. This makes saving data, and import/export of waypoints, tracks or routes much easier. It supports various Global Navigation Satellite Systems such as GPS, Galileo2, GLONASS, QZSS2. It also offers… Read Full Review.

Furuno GP1870F GPS Fish Finder$600 – $1,000
Furuno GP1870F

Although the Furuno GP1870F is a medium size unit, with boasting only a 7-inch display, it actually is quite an advanced chartplotter. The actual unit only comes with basic charts, but they can be upgraded to C-Map by Jeppesen, including 3D charts and satellite images. It’s a unit that offers quite a few extremely useful navigation and fishing functions, such as Tide Info, and C-Weather. It’s quite a precise marine GPS, which also uses SBAS for correction. In terms of sonar, it offers dual frequency 200/50 kHz, which makes it a great unit for deepwater fishing. Bottom discrimination is a function specific to the Furuno units, and this one comes with it, along with… Read Full Review.

Over $2000
Humminbird SOLIX 12 CHIRP GPS

The SOLIX 12 CHIRP GPS is one of the largest units sold by Humminbird. It doesn’t have Side Imaging or Down Imaging but does offer DualBeam Plus CHIRP Sonar. With the included XNT 14 20 T transducer, it can use the High and Medium Range CHIRP, with a frequency modulation between 75-95 kHz and respectively 175-225 kHz. The unit is equipped with a fast and accurate internal GPS, and comes with two built-in chart bundles – Humminbird Mapping and a Navionics-based charts database. It also has the AutoChart Live feature which allows you to map the contours of your lake as you go… Read Full Review.