- Get quality GPS tracking with the high-sensitivity GPS 158i, a 5” grayscale standalone GPS with easy-to-use features that fit both your boat and your budget. Mariners will be able to acquire satellite signals quickly and accurately, regardless of their position, thanks to the high sensitivity GPS receiver and WAAS capability. It also features a built-in BNC external antenna connector. The increased memory in the GPS158i allows user to store up to 3,000 waypoints and 50 routes.