When you add optional BlueChart g2 Vision cartography, the features of this Garmin marine GPS receiver only get better. BlueChart g2 Vision on the Garmin GPSmap 521S GPS Receiver allows users to see marine chart detail such as detailed coastlines, depth contours, tidal stations and more. Garmin GPSmap 521S Marine GPS Receiver: * Large, ultra-bright 5" diagonal QVGA display * 234 x 320 pixels * NMEA 2000-certified for seamless integration with the Garmin marine lineup * Preloaded worldwide marine basemap * Compatible with GXM 51 for XM Radio and XM WX Satellite Weather * Built-in high-sensitivity GPS receiver * High-speed processor for fast screen redraws and smooth panning * SD card slot * Backlit keypad for easy operation in low light conditions * Power output: 500W (RMS), 4000W (peak to peak), dual frequency * Depth: 1,500"/500m (dual frequency) * Uses a dual frequency transducer 50KHz (45 degrees), 200KHz (10 degrees) for maximum saltwater performance * Patented transom/trolling mount transducer * Ultrascroll high rep rate sonar provides lightning-fast screen updates * Autogain technology enhances target visibility * See-Thru technology shows weak and strong returns simultaneously * Water temperature log graphically records water temp data * A-scope * Whiteline * Adjustable depth line helps gauge desired fishing levels and bottom clearance * Split zoom display offers a closer look at fish targets and bottom structure * 2x, 4x and bottomlock zoom * Adjustable keel offset * Alarms for fish size, shallow water, deep water and low battery * Garmin 521S GPS Receiver Includes transom mount transducer, power/data cable, mounting bracket with tilt/swivel and protective front cover