This is the latest DEM (Digital Elevation Model) routable Basemap, it will update your preloaded one, but not necessary to update it IMHO
[Only registered and activated users can see links. ] read post 3
DEM are for displaying shadings on terrain
The standard map coverage includes: (but it depends on regions)
Oceans, rivers, major streams and lakes (greater than 5 sq. miles)
Principal cities and urban areas, with many smaller cities and towns
Major interstates, principal highways, and State/Province level roads
Political boundaries (state and international borders)
Major Airports
Railroads