Garmin's boating specific GPS Map 78S includes an electronic compass as well as a high sensitivity receiver and floatable housing. The electronic compass uses a 3 axis tilt to show your heading whether you're standing still or spinning around on a paddle boat. With a WS enabled GPS and HotFix satellite prediction, the GPS Map 78S locates your position quickly and maintains your location in deep canyons. USB computer compatibility lets you download detailed marine, topographic, road, and hiking maps for versatile adventures. There's a built in memory with 1. 7GB of space, and Garmin added a slot for your own microSD memory card. The dual battery system accepts two standard batteries, lithium, or NiHM battery packs.