The GPS 152 Marine Navigator is a 12 parallel channel GPS receiver loaded with a database of American cities and nautical navigation aids such as lights, buoys, sound signals, day beacons and tide data. Built-in memory of one megabyte makes the GPS 152 Marine Navigator compatible with Garmin's MapSource Points of Interest CD. With this CD and the GPS 152, you add additional marine navaid detail to your unit. In addition to larger memory, the GPS 152 Marine Navigator is compatible with the Wide Area Augmentation System (WAAS), a technology designed to improve the accuracy of GPS positioning to about three meters.