The GPSMAP 188C Sounder installs easily in open cockpit and overhead boxes, and features a quick map redraw using a high-speed RISC processor. These units combine chartplotter and sounder capabilities in one unit, with split-screen capability so you can view your position and sounder information at the same time. For the GPSMAP 188C Sounder, the display is a high-resolution (234 x 320 pixels), 16-color TFT display. Featuring a built-in worldwide basemap, the GPSMAP 188C Sounder is fully compatible with Garmin's new BlueChart marine cartography and many MapSource CD-ROM products, including Fishing Hot Spots. These units are designed to provide precise GPS positioning using correction data obtained from the Wide Area Augmentation System (WAAS). They also provide position accuracy to less than three meters when receiving WAAS corrections. The GPSMAP 188C Sounder also accepts RTCM-104 differential corrections. The 188C's Sounder features include: 50/200 khz transmit frequency with transmit power 500 watts RMS (4000watts peak-to-peak), split screen combining both map and sounder data, graphic white line for clear image of bottom hardness and structure, underwater waypoints to capture position and depth, auto bottom tracking w/ 2X, 4X zoo and See-Thru technology separating fish from thermoclines and structure. Unit Dimensions: 6.30"W x 6.18"H x 3.25"D.