The Garmin Quickdraw Contour feature requires that a yacht have the following in order for its users to generate contour maps for detailed map information viewing: sonar depth, your GPS position, and a memory card with free space.
When a contour map is drawn, green, yellow, and red circles indicate good to bad depth, GPS, and speed, respectively. Contour maps can be saved to a memory card for later use. In addition, the contour quickdraw community online is a public sharing of contour maps that other users created.