[CA] can you tell what this black thing is?

[ray18]

can you tell what this black thing is?
What does black color mean in my Axiom 9" MFD with RV100?

[Chuck - Raymarine - Moderator]

Welcome back to the Raymarine Forum ray18,

All that may be stated is that it appears to be an object on the bottom. Unfortunately, there is insufficient image detail to provide any further insight as to what it may be. The black colored area is the sonar shadow cast by the object.

[ray18]

ok thanks.
it looks like part of it was above the water. I know I did pass a square shape cement intake for overflow in the dam area of the lake. Just not sure why the image came out to be round top shape instead of square shape.

[Chuck - Raymarine - Moderator]

Ray18,

Objects having vertical height above the bottom will cast sonar shadow. As an object's height above the bottom increases, so will the size of its sonar shadow. Best SideVision and DownVision image is accomplished when the vessel maintains a relatively constant speed 3-5 MPH with little roll. When trying to identify an object it often helpful to pass the object from different directions. As with all sonar imaging, experience gained through use of the product combined with knowledge of the underwater structures will over time permit you to increase your ability to identify underwater objects.