Mapping Real-Time Mapping

Real-time mapping is a feature on many modern fish finders that automatically generates custom depth contour maps from your sonar readings as you travel across the water. The unit records depth data at each GPS position, processes it into contour lines, and displays the map in real time on your chartplotter. Over a fishing session or multiple trips, you build a detailed custom map of your fishing waters.

Each major brand offers their own version. Garmin calls it Quickdraw Contours. Humminbird offers AutoChart Live. Lowrance and Navionics provide SonarChart Live. While the implementations differ in detail, the core function is the same — recording sonar depth data, tagging it with GPS coordinates, and rendering it as contour lines on the map display.

Real-time mapping is most valuable on lakes and waters where commercial mapping data is limited, outdated, or nonexistent. Private ponds, newly impounded reservoirs, rivers with shifting channels, and foreign waters where mapping coverage is sparse all benefit enormously from the ability to create your own depth maps. Even on well-mapped lakes, real-time mapping can reveal current conditions that differ from survey data collected years ago.

For the best mapping results, drive at a consistent moderate speed in overlapping passes that cover the area systematically, like mowing a lawn. Erratic speeds and widely spaced passes create gaps and inconsistencies in the contour data. Many anglers dedicate pre-fishing trips to mapping sessions, covering key areas methodically to build accurate maps they will use for the rest of the season.