Understand 2D, Down Imaging, Side Imaging, and MEGA Channels

Use this when

You are looking at a recording with multiple channels and are not sure which one to review first, or you want to know what each channel is actually showing you.

2D sonar

2D (also called Traditional) sends a cone-shaped beam straight down from the transducer. The image shows a vertical slice of the water column beneath the boat. Targets appear as arches when the boat passes directly over them.

The two common 2D frequencies are 83 kHz and 200 kHz. The 83 kHz beam covers a wider area but less detail. The 200 kHz beam is narrower with finer detail. In HumVision these channels appear as 2D 83 and 2D 200 in the channel tabs.

2D is most useful for confirming depth, spotting suspended targets at mid-water, and checking bottom hardness.

Down Imaging

Down Imaging sends a thin, fan-shaped beam straight down. Instead of arches, targets appear as sharp vertical lines or distinct shadows. The result looks more like a photograph than a traditional sonar chart, which makes it easier to identify the shape of what is below.

HumVision shows Down Imaging as DI 455, DI 800, or MEGA DI (1200 kHz), depending on the frequency the unit recorded. Higher frequency means finer detail but shallower range. MEGA DI gives the most detail in shallower water where depth penetration is less of a concern.

Down Imaging is typically the best starting channel for target review. The image clarity makes it easier to spot objects, debris, and anomalies on or near the bottom.

Side Imaging

Side Imaging sends a fan-shaped beam out to both sides of the boat. It maps the bottom laterally, giving you a bird's-eye view of the terrain to the left and right of the boat's track.

The image shows the area swept by each pass. Objects that stick up from the bottom cast a bright return followed by an acoustic shadow. The length of the shadow relates to the height of the object above the bottom.

HumVision splits Side Imaging into port (SI Port or MEGA Port) and starboard (SI Stbd or MEGA Stbd) tabs, because the two beams are recorded as separate channels. Review both sides independently. The shadow-height tool in the toolbar can give you a rough estimate of target height using the shadow length.

Side Imaging is most useful for covering wide areas quickly, locating objects that are lying on the bottom, and estimating the physical profile of a target.

MEGA

MEGA is Humminbird's high-frequency extension. MEGA DI records at 1200 kHz instead of 455 or 800 kHz. MEGA SI records Side Imaging at 1200 kHz. The higher frequency produces finer spatial resolution but reduces depth penetration.

In HumVision, MEGA channels appear as MEGA DI, MEGA Port, and MEGA Stbd. Not all units or recordings include MEGA channels. If the tabs are absent, the recording does not contain them.

Use MEGA in shallower water when you need the clearest possible image of a suspected contact. MEGA is short-range by design; depth penetration is limited compared to lower-frequency channels.

Which channel to use when

• Starting a review — open DI 455 or DI 800 first. Down Imaging gives you the clearest picture of what is on the bottom.
• Shallow, clear water — switch to MEGA DI if available. The detail improvement is significant.
• Checking a wide area — use SI Port and SI Stbd. Cover both sides before concluding nothing is present.
• Estimating target depth or water column — 2D gives you the depth scale and shows suspended targets that Side and Down Imaging can miss.
• Confirming a contact — review the same ping on multiple channels. A real target typically appears consistently across 2D, DI, and SI.