GPS from Garmin, makers of affordable, easy to use Global Positioning System navigation systems for hikers, boaters, hunters and automotive travel. Simply put, a GPS receiver is sensing information from several orbiting satellites in different positions at the same time. Based on this information the receiver is able to determine your latitude and longitude anywhere to within +/-10 meters. Many newer GPS units are WAAS (Wide Area Augmentation System) capable, allowing greater accuracy without the need for any secondary antennas that were previously required to receive a more accurate differential GPS signal. GPS and WAAS are free services in that no subscription fees are required to access the signal. GPS units differ in features, some are used only for position locating, others display high quality street maps, others are more marine oriented. Some units allow the addition of external antennas for greater sensitivity. Units with mapping capability also differ with the amount of internal memory available to add more detail to the map. All our GPS handhelds can be connected to a home computer or notebook, allowing you to upload/download stored waypoints and tracks, and to use the GPS with real-time navigation software that will display your course and position. Garmin offers the ability to add more street detail using their MapSource CD's, while certain models will allow the use of their exciting new BlueChart Marine Cartography.