What is sonar and how does it work?
The word 'Sonar' is an acronym: SOund Navigation And Ranging. Using sonar, objects can be detected by emitting sound pulses. The sound emitted by these objects themselves is used to determine their distance. This technology can be used not only to measure water depths, but also to detect fish.
What frequency for my sonar device?
Sonar devices work with different frequencies. With traditional sonar these are between 50 kHz and 200 kHz.
Low frequency signals are less absorbed and are thus able to travel further distances before becoming too weak. Measuring therefore reaches deeper depths. With a large beam angle, low frequencies can be used to monitor a large area. A low frequency range (low CHIRP) of 50 kHz or 80 kHz is suitable for measuring greater water depths of more than 60 meters. Low frequency transducers have lower resolution and definition than high frequency transducers and are less susceptible to interference.
Mid-range frequencies of 80-160 kHz or 83 kHz are ideal for detecting fish in shallow waters.
The higher the frequency, the wider the cone of transmission and the flatter the measurement. Image resolution is better at high frequencies than at low frequencies. It is recommended to use a transducer with a higher frequency if you are travelling at higher speeds. For water depths up to 60 meters, we recommend a frequency of 200 kHz. Frequencies of 455 kHz show the seabed structure in detail, and at 800 kHz a near photo-realistic image is produced.
What is a CHIRP fish finder?
CHIRP stands for Compressed High-Intensity Radiated Pulse. CHIRP sonar is the most modern type of fish finder system. Highly compressed energy pulses or sound waves can be transmitted and received simultaneously at higher and lower frequencies. CHIRP Fish finder usually has the frequencies 83/200 kHz (Med / High) and 50/200 kHz (Low / High).
Higher frequencies produce detailed echoes and lower frequencies reach further distances. In this way, the CHIRP sonar receives several pieces of information and can create a detailed sonar image from this. Targets can be better identified due to the different frequencies. This means that even fish that are swimming close to each other or on top of each other can be clearly distinguished. Good echo separation makes it easier to identify living organisms from the surrounding structure.
Conventional fish finder without CHIRP technology can only transmit and process one pulse in succession at a fixed frequency. The resulting image is much less detailed than a modern CHIRP fish finder image. CHIRP sonar devices are also much less prone to interference. A separate frequency range is created for receiving echoes, which makes it possible to distinguish between true sonar echoes and interference.
Above image: conventional fish finder
Below: CHIRP fish finder
Generally speaking, CHIRP fish finders feature a crescent-shaped fish finder view. CHIRP fish finder transducers detect sound waves reflected from the swim bladders of fish and other objects directly under your boat. The display shows you these echoes depending on the distance to the transducer. The colouring of the received echoes varies from manufacturer to manufacturer and becomes correspondingly more vivid as the intensity of the echo increases.
Sonar technology from Raymarine, Garmin, Lowrance, B&G and Simrad
Fish Finder with DownScan / DownVision / ClearVü
DownScan, DownVision or ClearVü technology photo-realistically maps the seabed structure with the aid of high-frequency sonar sensors. Thanks to high frequencies of 455 and 800 kHz, more information is picked up by the transducer and this can be then be displayed in correspondingly high detail. This means there is hardly any need for interpretation when reading the displayed sonar images, so you can easily distinguish between fish and rocks or other objects.
The corresponding transducers operate with a wide cone of transmission of up to 45° and thus cover a wide area.
This representation makes it possible to detect previously undiscovered underwater structures and to identify new fishing hotspots.
However, their range is limited due to the high frequency of the transducers, which lies between about 40 and 70 metres. This range is perfectly adequate in many European fishing waters.
Thanks to new technologies, such as Raymarine HyperVision or Garmin LiveScope, it is possible to display even more detail faster with frequencies of up to 1200 kHz.
Depending on the manufacturer, the technology is named differently:
- Raymarine = DownVision
- Lowrance, B&G, Simrad = DownScan
- Garmin = ClearVü
Depending on the manufacturer, the technology is named differently:
- Raymarine = SideVision
- Lowrance, B&G, Simrad = SideScan
- Garmin = SideVü
Fish Finder with SideScan / SideVision / SideVü
With SideScan, SideVision or SideVü the echo is beamed out on both sides of the boat. Similar to DownScan, DownVision or ClearVü technology, photo-realistic underwater images are shown on the display unit thanks to high frequencies of 455/800 kHz. Due to further developments, such as Raymarine HyperVision or Garmin LiveScope, the performance of the transducer is even higher and the bottom structure is shown in much more detail.
Unlike DownScan technology, with SideScan the sonar image travels from top to bottom and not from right to left. The further down you look at the image, the further away the spot is from the boat. The mostly dark strip in the middle of the SideScan image is the water column directly under the boat. The SideScan image extends outwards along the water column.
SideScan, SideVision and SideVü technology has the advantage of covering a wider area of up to 75 m on each side of the boat at once. Therefore, it is possible to find good fishing hotspots much faster. To get the best results, it is important to keep the boat moving as straight as possible during scanning and as slow as possible at a speed of max. 15 km/h.
FIG (water column opened out)
RAYMARINE Sonar Technology
HyperVision down (DownVision)
HyperVision side (SideVision)
Transducers with Raymarine Hypervision Technology
The Raymarine Hypervision technology combines the following functions in only one transducer or thru-hull transducer pair:
- CHIRP fish finder
- DownVision (bottom structure view directly under the boat)
- RealVision (3D view)
The special feature of Hypervision technology is the very high frequency of 1.2 megahertz, which delivers crystal clear down, side and RealVision images to a depth of 30 meters (100 feet). By switching to the 350 kHz standard CHIRP sonar, you can increase the range to 180 m (600 feet). When using the 200 kHz sonar type, ranges of up to 270 m (900 feet) can be achieved.
Compatible transducers & chart plotters
Raymarine RealVision Sonar
RealVision view provides a 3D representation of the subsurface. This view makes it much easier to interpret echoes and gives a quick, detailed overview of what is under your boat. The lifelike display of underwater structures makes it much easier to identify hotspots and shoals of fish.
Like Hypervision Sonar, RealVision supports both DownVision, SideVison and CHIRP Fish finder frequencies.
FIG: RealVision, Down-, SideVision
and CHIRP split screen
Realvision with Overlay
Compatible transducers, plotter & transducer sets
GARMIN sonar technology
Garmin Panoptix Forward Sonar Technology
Depending on the transducer, Panoptix Forward technology combines a three-dimensional forward view (RealVü 3D Forward) with fish finder data, a fish finder forward view (LiveVü Forward) with which you can see the fish in front of you and a pure 2D forward view (FrontVü) with a range of 90 meters (300 feet).
FIG: RealVü 3D Forward
Garmin Panoptix Down Sonar Technology
Depending on the connected transducer, Panoptix Down provides a real time fish finder view (LiveVü Down), a 3D view of the bottom structure under your boat (RealVü 3D Down) and a 3D gradient view of the bottom structure along your route (RealVü 3D Historical).
FIG: LiveVü Down
RealVü 3D Down
RealVü 3D Historical
Panoptix transducer compatibility
|RealVü 3-D Down|
|RealVü 3-D Historical|
|RealVü 3-D Forward|
Garmin LiveScope Sonar Transducer
Garmin LiveScope technology delivers high resolution, easy to understand live sonar images, even when you are not on the move. The transducer can be adapted to your respective fishing technique by adjusting the alignment. Tilt the transducer forward to see what is to the side of you or point the transducer downwards to analyse what is happening directly under your boat.
Furthermore, the new LiveScope Perspective view lets you choose a predictive LiveScope Down view (separate transducer mount required).
These images show the clarity of LiveScope Down technology:
A bridge and a piece of road
A shoal being chased by bigger fish
The remains of a fundament
The remains of a fundament and a second building
LiveScope allows you to view down to a depth of 60 metres under your boat and 60 meters to port and starboard.
NAVICO Sonar Technology
Navico Fish Finder with ForwardScan
The Navico ForwardScan transducer provides a clear 2D image of the subsurface in front of you. The maximum forward view depends on the present water depth. The ForwardScan-transducer can "look ahead" by a maximum of 8 times the current depth. Example: With a water depth of 5m, you can look up to 40m ahead. In this way you will always have an overview of the real depth even in poorly charted waters. This technology is particularly useful when looking for a suitable place to anchor and to avoid running aground in shallow waters.
Navico LiveSight Transducer
With LiveSight sonar technology from Navico you can see fish movements in real time, similar to Garmin LiveScope-technology. This allows you to see how fish react to bait dropped and makes it a lot easier to interpret the sonar image. In addition to LiveSight view, the LiveSight transducer also supports the traditional CHIRP fish finder frequencies, so both images can be placed next to each other on a split screen to find ideal fishing spots.
With the help of the Navico PSI-1 LiveSight sonar module, you can also use the LiveSight technology on devices without an integrated LiveSight module, such as with the Simrad NSS evo3 series.
The transducer can look down or forward, depending on its setting:
Navico FishReveal sonar
The Navico FishReveal function places an overlay of CHIRP fish finder echoes on the Downscan view. This combination facilitates the interpretation of the echoes and gives you a quick overview of individual fish or shoals without cumbersome displays which are difficult to see and interpret on small screens.
Navico TripleShot Transducer
Depending on the depths at which you want to fish, you should spend time choosing the right transducer. If you use a TripleShot-transducer you will get detailed echoes, both in shallow and deep water.
|83/200 HDI||50/200 HDI||TripleShot|
|Single Frequency Sonar||
|Different CHIRP frequencies of 50/200 kHz or 80/160 kHz. „Traditional“ fish finder view.||Different CHIRP frequencies of 50/200 kHz or 80/160 kHz. „Traditional“ fish finder view.||Different CHIRP frequencies of 50/200 kHz or 80/160 kHz. „Traditional“ fish finder view.|
|Photorealistic images of the area below the boat through high frequencies of 455 & 800 kHz. Range only about 40-70 m.||Photorealistic images of the area below the boat through high frequencies of 455 & 800 kHz. Range only about 40-70 m.||Photorealistic images of the area below the boat through high frequencies of 455 & 800 kHz. Range only about 40-70 m.|
|Photorealistic images through high frequencies of 455 & 800 kHz of the area at the side of the boat. Range approx. 75 m per side||Photorealistic images through high frequencies of 455 & 800 kHz of the area at the side of the boat. Range approx. 75 m per side||Photorealistic images through high frequencies of 455 & 800 kHz of the area at the side of the boat. Range approx. 75 m per side|
|Panoptix Forward||Forward Scan|
Depending on transducer:
• RealVü 3D Forward: 3D forward view
• Fish finder data
• LiveVü Forward: Fish finder forward view
• FrontVü: 2D forward view (90 m range)
• 2D forward view
• Depends on water depth. Range max. 8 times water depth
• 3D representation of the subsurface in real time
• Frequencies up to 1200 kHz
• Detailed & fast display
• Live echo images, even when stationary
• CHIRP Frequencies
• High frequencies for detailed display
• Fish movements in real time
• Traditional CHIRP frequencies
• Split Screen
• 1.2 mHz frequency
• Crystal clear images up to 30 m
• CHIRP (bis 180 m)
• Down Vision
• Side Vision
• Real Vision (3D) real time
Depending on transducer:
• LiveVü Down: • Real-time fish finder view
• RealVü 3D Down: 3D view of the underwater structure under boat
• RealVü 3D Historical 3D gradient view of the ground structure along the route
|• Overlay of CHIRP fish finder echoes in DownScan view for quick overview without split screen display|
• 50 m, 200 m & 300 m frequency
• Can be used both in shallow and deep water
* (Simrad, B&G, Lowrance)
Written by our SVB (technical) experts
Our team of SVB technical experts is there to give our customers professional advice on all matters relating to technology on board. With specialist know-how, extensive training, and a technical flair for electrical connections, fittings etc, our crew are more than qualified to advise our customers.