Garmin's state-of-the-art GPSMap 840XS Combo blends high-performance chart-plotting capabilities with Clear sonar views. DownV technology produces clear, precise HD-ID Sonar images and a nearly photographic sonar view of fish and structure under your boat. Easy-to-see, large 8" SVGA full-color display. 10Hz-GPS updates your position and heading 10 times per second. Mark and navigate to up to 5,000 waypoints. Comes with an all-in-one Transducer for DownV  with CHIRP technology and 77/200khz. 500-watt Transmit power with water-surface temperature. Record and review sonar Readings. Wirelessly connect to your Apple iOS device for BlueChart Mobile. Two micro-SD slots for additional storage. Combo includes LakeV HD maps with over 17,000 lakes, plus over 5,700 HD lakes and BlueChart g2 coastal maps.