Marine electronics and navigation specialist, Errol Cain has supervised the installation of marine electronic systems into thousands of Riviera luxury cruisers in his 29 years experience. In this issue, Errol talks about the latest releases from Raymarine and Garmin.
Depth sounders have been around for a long time in either digital or picture models and most modern vessels have one fitted.
There have, however, been recent changes in fish-finder technology with most traditional sounders moving from analogue to digital or CHIRP (Compressed High-Intensity Radar Pulse) to give a much clearer picture of what’s lurking below your vessel.
This is great news for navigation and fishing but sounder technology has progressed even further than this, and I will attempt to explain here.
Let’s start with a brief overview of CHIRP then look at the newer developing technology of CP100 DownVision/ CP200 SideVision (Raymarine), GVC10 SideVu/DownVu (Garmin) and forward-looking future sounders …
What is CHIRP?
CHIRP (Compressed High-intensity Radar Pulse) is a frequency-modulated sound (sonar) pulse. Traditional echo sounders rely on a distinct frequency pulse rebounding off fish, an object or the bottom (50 kHz for deep water fish-finding, or 200 kHz in shallower water).
The amount of energy required for the signal to reach the bottom in deep water when using a low frequency signal (say 50kHz), requires a long sonic pulse (possibly 40m in length). Any objects that are closer together than the length of this pulse will not show up as separate objects on the fish-finder screen. CHIRP technology modifies the pulse that is sent by the transducer.
Instead of transmitting a distinct pulse beneath your boat, CHIRP technology modifies the pulse so ranges of frequencies are transmitted by the transducer (say 28 to 60 kHz, or 130 to 210 kHz, or 42 to 65 kHz). When you transmit a modulated pulse across these ranges, targets that are closer together than a particular pulse length, reflect that pulse at a different frequency to those further apart than the pulse length, and each will show up separately on the monitor. This range, or pulse sweep, is known as the bandwidth, hence the term broadband sonar. The echo signal return from a target is the same as the frequency with which the target was struck, so two targets even close together in shallow water will return a slightly different frequency signal. The result is quite simply, stunningly improved separation and detail.
All the major sounder manufactures offer CHIRP sounders as follows with model identifier; Furuno DFF1UHD, Garmin GSD26, Raymarine CP450C, Simrad BSM-2.
DownVision / DownVu
The CP100 DownVision and DownVu options as offered from Raymarine and Garmin use CHIRP technology but in a different way.
I’ll let Raymarine and Garmin explain this one.
“The CP100 network sonar module brings CHIRP DownVision technology to Raymarine’s multifunction displays. CP100’s CHIRP DownVision delivers a photo-like view of the world beneath your boat, allowing you to image bottom structures with amazing detail and target fish simultaneously.
“Unlike conventional imaging sonars that transmit a single frequency with each pulse, the CP100 uses CHIRP technology to transmit across a wide spectrum of sonar frequencies with each pulse – the result is much higher resolution, photo-like sonar images.
“The CP100 is the ideal sonar solution for freshwater anglers. Combined with Raymarine e-Series HybridTouch displays, the CP100 lets freshwater anglers create a multi-display network with HybridTouch control.
“Photo-realistic CHIRP DownVision easily identifies the habitat of bass and other freshwater species. With depth performance up to 600ft, the CP100 is the perfect choice for coastal and bay fishing, imaging wrecks with unmatched fidelity and using the second CHIRP channel to target bait and predators.
“This high-frequency sonar gives you a clearer picture of what’s below your boat, by producing a more detailed representation of objects, structure and fish. DownVu with CHIRP technology takes it one step further, producing an ultra-clear image with even more detail.”
It starts to get even more interesting with the CP200 SideVision and GCV10 SideVu. These are add-on modules to existing multi-function displays for viewing sideways under water.
This was previously only achievable with the likes of the Furuno CH300 scanning sonar that will set you back about $40k (installed). Now, for a fraction of that price, we can also view sideways.
Here’s what Raymarine and Garmin have to say about these options.
“The CP200 CHIRP SideVision™ Sonar expands your underwater horizon with crystal-clear, bank-to-bank displays of fish, bait and underwater structure.
“Engineered with the same CHIRP sonar technology as Raymarine’s award-winning DownVision™, the CP200 uses advanced CHIRP signal processing technology to let you see further, see more clearly, and detect more fish than traditional side-scanning sonars.
“SideVu shows you what is happening to the sides of your boat – an excellent way of finding structure and fish. SideVu with Chirp technology provides an even more detailed and higher resolution image of what is beneath the surface.”
Both the Garmin and Raymarine Down and Side view sounders are available with through-hull and transom-mount transducers, making them ideal for a cruiser and tender.
So with all this new technology at our fingertips, fish have nowhere to hide but what about seeing what’s in front of us?
There are a few products currently available, like the Furuno searchlight sonar mentioned previously or the Echopilot, as well as a range of yet-to-be-released products like the Simrad ForwardScan.
Simrad announced its new product this some time ago but as yet it hasn’t been released for sale.
There is an excellent article at Panbo for anybody that is interested in forward-scan technology.
If you would like to read this article please click here
There is another great little forward-scan brand called Interphase, which was purchased by Garmin a few years ago. With Simrad having announced the imminent release of their ForwardScan sounder, you would imagine that Garmin would follow very shortly as well.
No word from Raymarine or Furuno on forward-scan sounders but I bet they are working on it.
For further information on any of the above, please contact;
+61 7 5561 7900