GPS sounder handset

Choosing a GPS fishing sounder !

Some fishfinders have a GPS locator to record your favorite waypoints, tracks and fishing spots.

The main difference is that the GPS Echosounder combo will allow you to add an optional navigation chart that will provide all the details such as sounding lines, harbor entrances, buoys and beacons, wreck positions... and for the most advanced devices like Garmin GPS: an automatic "autoguiding" route creation function. Or Lowrance echo sounders like the Lowrance HDS 12.

Touch screen or button for my boat GPS?

The definition will give better quality details. The more pixels you have, the better the quality. A large screen, expressed in inches, allows for better readability but especially a split view of the different information: one side sonar, one side map. Ideal for having all the information at a glance.

Then there is the question of a touch screen, a screen with buttons... or now a hybrid GPS: touch + buttons! Despite what you might think, touchscreen GPS are very robust and resistant to sea water. No buttons = no risk of water infiltration. However, remember to have a cloth nearby to wipe off fingerprints.

For your information, however, we do not recommend choosing a GPS plotter/depth finder handset that is smaller than 7 inches.

Which function for my GPS Plotter and Fishfinder handset?

It is important to define your needs and the evolution of the product before purchasing a boat GPS. In addition to the main GPS Plotter and Fishfinder functions, some units offer additional connectivity:

• Radar boat to visualize the surrounding vessels 
• Reversing camera for maneuvering in port
• Connection AIS for anti-collision safety
• Remote WIFi referral on tablet 
• Probe on the front anti-washout
• Bathymetric survey

For example, if you are equipped with a radar, you will need to turn to a multifunction radar display such as: Helix G4N or HDS, GPSmap XSV. But if you need a powerful GPS plotter sounder but no extra tricks, you can count on a Garmin Echomap, Lowrance sounder Hook Reveal ...

What technology do I need?

Sounder technologies are similar for the different brands offered on the market.

First of all, the CHIRP, basic technology that scans the bottom with a wide frequency spectrum allowing to have a clear image of the bottom with a correct fish discrimination. 

Let's go one level further with the Down Vu technology, this denomination at Garmin taken over by Humminbird in Down Imaging allows to see under the boat with an almost photographic quality. This technology is declined for the higher models in Side Vu (or Side Imaging) which allows this time to see what happens under water on the sides of the boat. The devices equipped with the SIDE, are also equipped with the DOWN, and the CHIRP.

Finally, the UHD technology from Garmin is an evolution of the previous technology, with even better quality, and unmatched sharpness. Humminbird offers the equivalent with the Mega Side Imaging+ available on the following devices: Helix 8G4N Chirp Mega Si+, Helix 9G4N Chirp Mega Si+, Helix 10G4N Chirp Mega Si+, Helix 12G4N Chirp Mega Si+, or Solix 10G3 Megasi+, Solix 12G3 Megasi+

Material of the probe:

• Plastic probe: recommended for polyester and metal hulls.
• Stainless steel probe: recommended for steel or aluminum shells.
• Bronze probe: recommended for polyester or wooden hulls.

Installation option:

• Transom Sensor: recommended for outboard motor boats and Z-Drive base.

Easy to assemble, its installation still requires some precautions:

• The probe is always immersed.
• Perfectly horizontal mounting.
• The location is not behind the propeller, which would interfere with the signal.
• The probe is positioned a little lower than the hull, avoiding disturbances to the hull.

• Thru-hull sensor: recommended for inboard motorboats, IPS pods, or Zeppelins

A through-hole transducer works well at high speeds. It is the preferred type of transducer for experienced anglers. Installation requires drilling into the hull, and the location must be chosen carefully: An easily accessible place to tighten the nut inside the hull. At the beginning of the last third of the hull, ideally near the centerline and in front of the engine. Never near intakes, valves, anodes, speedo sensors, keels, propellers, shafts or hull strakes. Internal mounting probe: for any polyester boat, not laminated (direct access to the strat)

No hull drilling is required for this type of transducer. The transducer is simply glued to the bottom of the hull, in an oil bath, and the signal passes through the hull. Disadvantage: 

• reduced performance due to transmission through the hull. 
• degraded fish detection (except 1000w model)
• limited depth detection
• No water temperature.

Power:

Power is the force at which the probe emits electroacoustic pulses. This power is expressed in watts RMS. Increasing the transmitting power increases the chance of receiving a return echo at greater depths or in water with poor propagation conditions. It also allows more detail to be displayed, such as bait and structure features. Generally, the higher the power, the greater the depth available and the better the discrimination detected from real echoes such as fish and bottom structure.

Probe frequency:

The higher frequencies (200 kHz) use narrow beams and are most effective in depths less than 60 meters. Even at high speeds, the display is accurate and usable. The higher frequencies create a more detailed image, and better target definition allows detection of very small objects.

Lower frequencies (50 kHz) use wider beams, allowing anglers to find more targets, but with reduced definition and target separation. Although lower frequencies allow you to reach greater depths, they do not always provide a clear picture of the bottom.

Good practice is to use the 200 kHz frequency for a detailed image down to 60 meters and the 50 kHz frequency at greater depths. Even better is to display both frequencies side by side on a split screen.

A CHIRP sounder continuously scans the bottom over a range of low, medium and high frequencies (depending on the sounder) in a single sweep. The returns from each frequency are then interpreted and displayed on the screen. The continuous sweep of various frequencies allows CHIRP technology to provide denser information and generate a sharper, higher resolution image, much better target separation and sharper fish arches than a traditional sonar. If several fish are grouped together, a conventional sonar unit will show only a single echo, whereas a CHIRP can differentiate between them. The same is true for fish that are close to the bottom. The sonar can "break them up".