Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock () or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Example of coregistered NED and SRTM and the derived difference grid for an area in eastern Kentucky. The length of the profile is about 5.8 kilometers.
Public Domain.
