The USGS has global DEM data at several resolution levels: 30-arc-second (1 kilometer), 15-arc-second (450 meters), and 7.5-arc-second (225 meters). The GMTED2010 dataset with multiple resolution levels replaces a former version called GTOPO30, which only had the resolution level of 30-arc-second (1 kilometer). These data have been collected from a variety of sources using aggregation methods. These datasets are best used for working at the continental scale and with very large regions. More information is available in the USGS publication.
The data can be accessed via the Earth Explorer site. First define your region of interest under the Search Criteria tab. You can upload a Shapefile (in Lat/lon), a KML file, or use the view window extents. Next select the Data Sets tab and under Digital Elevation select GMTED2010. Click on the Results button at the bottom of the screen and data that meets your selection is placed in the Results tab.
Click on the Footprint icon to view the size of the tile. These cover a very large area. Click on the Download icon and you can select the DEM resolution; 7.5 Arc Sec (225m), 15 Arc Sec (450m), and 30 Arc Sec (1km).
These integer data use the Geographic “projection” (latitude/longitude), the datum is WGS84, and are provided in TIF format. There are seven products in each order including min, max, mean, and standard deviation. For most applications you will use the Mean identified with “gmted_mea” in the filename. More information about these different products can be found in the USGS document referenced in the first paragraph.
A copy of the global 30-arc-second (1 kilometer) GMTED2010 data has been downloaded for internal use to a server at the Yale Center for Earth Observation (YCEO). Please see a member of the YCEO staff for guidance in using these data.
ENVI Standard version 5.1 and above also has the 30-arc-second (1 kilometer) GMTED2010 dataset embedded into the application. Access these data from ENVI; select File | Open World Data | Elevation (GMTED2010). As of January 2016 ENVI software on the workstations in the YCEO Lab provide the 7.5 Arc Sec (~225m) GMTED2010 dataset in JPEG 2000 format.