Axiom Chirp and Downvision images

[Chuck - Raymarine - Moderator]

Stan,

Per the previously referenced FAQ, the base of cone being scanned by each ping when using CHIRP conical sonar is equal to 0.4434 * Depth. At 10', 20', 40', and 60' depths, the diameter of the base is 4.4', 8.9', 17.7', 26.6'. The angle of the beam produced by DownVision is significantly larger side to side axis than in the fore-aft axis. In contrast, the fore/aft dimensions being scanned by each ping when using DownVision is equal to 0.01222 * Depth. At 10', 20', 40', and 60' depths, the diameter of the fore/aft area being scanned with each ping is 0.1', 0.2', 0.4888, and 0.7332. The side to side area being scanned with each DownVision ping may be similarly obtained based on depth using the multiplier found within the referenced FAQ. As specified within the referenced FAQ, it is the differences in the shape of the area being swept by CHIRP and DownVision combined with color variation based upon strength of the sonar returns which make CHIRP (conical) sonar the sonar of choice for marking fish and DownVision the choice of choice of these two types of sonar when seeking the greatest detail for bottom structure and objects within the water column. Marking fish with DownVision may be enhanced through manual increases to the DownVision sonar Sensitivity settings (MENU->SENSITIVITY SETTINGS). While it is often possible for DownVision to show fish, it is generally recommended that CHIRP be used for this purpose.