Sonar units for ice fishing fall into two basic types: flashers and graphs. When deciding which type to buy, consider the fish species you plan to target, how you fish and your budget.
Simple, durable, reliable and powerful, flashers use coloured marks on a circular display to show fish movements in real time. This gives instant feedback on how the fish are reacting to your bait. Novices may find the display confusing, however.
These winterized versions of standard, open-water sonar units show data in a scrolling display or multiple windows, often with GPS coordinates. Many graphs also easily convert for use on a boat. The scroll display introduces a slight delay, reducing its usefulness in teasing fish to bite. However, most new graphs feature a real-time window or a flasher-style view, which remedies that problem.