ndep.gov
National Digital Elevation Program Home PageThe National Digital Elevation Program (NDEP). Was established to promote the exchange of accurate digital land elevation data among government, private, and non-profit sectors and the academic community and to establish standards and guidance that will benefit all users. Guidelines for Digital Elevation Data (Version 1.0). Who is the NDEP? US Geological Survey (USGS). National Geospatial–Intelligence Agency (NGA). Natural Resources Conservation Service (NRCS). US Army Corps of Engineers (USACE).
http://www.ndep.gov/