Garmin Lakevu HD Ultra Auto Guidance (6,300+ HD Lakes) - A Garmin exclusive, Auto Guidance directs you to your hot spots quickly by instantly creating an on-screen path for your boat to follow that avoids shallow water and other charted obstructions. Shown with Mariner Eye view. High Resolution Relief Shading adds visual depth to the 2-D map making it easier to interpret contours and find fish holding structure. Dynamic Lake Level (1600+ HD Lakes) - Allows you to adjust your maps to the lake's current water levels giving you a better idea of spots that are either accessible or too shallow to explore. Fisheye View (1600+ HD Lakes) - Underwater perspective shows 3-D representation of lake bottom and contours as seen from below the waterline. Interface with sonar data for customized view. COMPATIBLE UNITS - GPSMAP 527, 547, 721, 741, 820, 840, 1020, 1040, 7400, 7600, 8000, echo MAP 40, 50, 70 and 90 series