GPS Built-in maps

Every GPS receiver has an information page that shows waypoints and tracks. The page is a simple map that plots travel and locations. It doesn’t show roads, geographic features, or man-made structures. Some GPS receivers have maps that show roads, rivers, cities, and other features on their screens. You can zoom in and out to show different levels of detail. The two types of map receivers are

• Basemap: These GPS units have a basemap loaded into read-only memory that contains roads, highways, water bodies, cities, airports, railroads, and interstate exits. Basemap GPS receivers aren’t expandable, and you can’t load more detailed maps to the unit to supplement the existing basemap.
• Uploadable map: More detailed maps can be added to this type of unit (in either internal memory or an external memory card). You can install road maps, topographic maps, and nautical charts. Many of these maps also have built-in databases, so your GPS receiver can display restaurants, gas stations, or attractions near a certain location.

GPS receivers that display maps use proprietary map data from the manufacturer. That means you can’t load another manufacturer’s or software company’s maps into a GPS receiver. However, clever hackers reverse-engineered Garmin’s map format. Programs on the Internet can create and upload your own maps to Garmin GPS receivers; GPSmapper is popular.
A handheld GPS receiver’s screen is only several inches across. The limitations of such a small display certainly don’t make the devices replacements for traditional paper maps.