GIS, CAD, and mapping daily news provided by Spatial News SpatialNews. They are more reliable at tracking in mountains and heavy tree cover. These mapping GPSs include a base map of all the Interstate, most of the state routes, railroads, rivers, and shorelines in the Western Hemisphere with seven levels of detail. An International version contains road maps of most countries in the rest of the world, and the Atlantic versions have higher-detailed maps of Europe. All have a Track Back feature that converts a track to 30 routepoints providing steering directions to navigate the Track Back route -either way.
All current units have icon symbols for waypoints.
All have a serial data or external power capability. The receiver performance in the Garmin GPS receivers is good enough, so that in many cases an external antenna will not be necessary. Reports indicate that you may need an external active antenna to maintain continuous coverage under difficult terrain and tree cover conditions. An MCX to BNC adapter cable is available if necessary. Garmin receivers are also compatible with most 3rd party amplified GPS antennas as well as Garmin brand.