Manufacturers of sonar fishfinders will almost always quote the display screen resolution of their product (if they don’t, they’re hiding something). The resolution on your computer monitor or home television might equate to just a pretty picture, but the display on your fishfinder is something a little more important.

Vertical Pixels

First lets look at vertical pixels. Each vertical pixel on your fishfinder’s display represents a slice of the sonar cone at a specific point (ping) in time. For example, if you are in 200 feet of water, and your vertical screen resolution is 200 pixels, then each pixel represents a foot of the water column. Think about that for a moment. Any target in that foot down there would be represented by a single dot on your display. If you are in very deep water, it would take a mighty big fish to take up several pixels; enough that it would draw your attention.

A more practical vertical pixel count would be something like, say 640. Let’s say you’re fishing in 30 feet of water. If that were the case, each pixel would represent 0.56 inches. So a fish 4” tall (about a 1.5 lb bass) would cover just 8 pixels.  Only 8 tiny little pixels on your display! Lower resolution would make this coverage even worse: 320 vertical pixels would result in 4 pixels covering the same fish---that’s not a lot of information about the fish.