We developed Natural Earth as a convenient resource for making custom maps. Unlike other map data intended for scientific analysis or military mapping, Natural Earth is designed to meet the needs of production cartographers using a variety of software applications. Maximum flexibility is a goal. Natural Earth Vector comes in ESRI shapefile format, the de facto standard for vector geodata. Character encoding is Windows-1252. All Natural Earth data use the Geographic coordinate system (projection), WGS84 datum +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs Intelligent data: The attributes assigned to Natural Earth vectors make for more efficient mapmaking. Most lines and areas contain embedded feature names, which are ranked by relative importance. Up to eight rankings per data theme allow easy custom map “mashups” to emphasize your map’s subject while de-emphasizing reference features. Other attributes focus on map design. For example, width attributes assigned to rivers allow you to create tapered drainages. Assigning different colors to contiguous country polygons is another task made easier thanks to data attribution. Source.