[CA] [CA11] Side scan issue

[Chuck - Raymarine - Moderator]

John,

We believe what you are seeing is normal, and it’s a matter of expecting the system to perform one way while it actually behaves differently. My first few times on the water with RV3D were similarly challenging, and disappointing, until I understood better how it works.

The SideVision channels transmit basically horizontally (slightly angled down) and effectively have much farther reach than the 3D does. If you take the SideVision out of auto range and select it manually, you can get it to see quite a distance with some detail. Its reach for all practical purposes in infinite, limited only by signal strength.

RealVision 3D on the other hand, can only see out to the sides about as far as the water is deep. The pattern of its beam is more of a radius that scrapes the bottom under the boat. To the sides, it does not have as much contact with the bottom. For this reason, its possible to pass relatively close to object that you would think it should see in 3D, and it in fact does not. At the same time, the 2D SideVision does pick them up.

Your situation may be a bit easier to interpret if we know the depth of the water when the video was taken, and whether or not the SideVision was in manual or automatic range control. The RealVision 3D’s range scale follows that of the SideVision, however, it can’t see as far as the SideVision can because of its radiused beam.

Sometimes when you get some thick bait, or noise on the RealVision 3D, you can actually see the radius of its beam in the returns, similar to spokes of a bicycle wheel.

Notice in your video how well the RV3D and SideVision both painted the bait pod he went through. It was well within the radius of the RV3D beam.

Take a look at the Brown’s Bridge Image attached below. This one is very impressive. Let me explain why. The water is nearly 90-feet deep, and the concrete bridge supports are only 25-feet away. In this case the RV3D beam is a 90-foot radius around the transducer, so we’re seeing the structure very nicely. Look at the SideVision image. It has solid returns on the bottom all the way to 120-feet away. Look at the horizontal scale on the RV3D though. Its bottom fades out at about 100-feet. Just a bit more than the water depth. The arc of the 3D beams is no longer in contact with the water out there.



Please additionally note that sonar improvements were included within the LH3 v3.11.42 software update and it would be recommended that this version of software be installed should it not already have been.