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.
The three levels of richness of the human movement data are shown: Level 1 (red squares), Level 2 (blue circles) and Level 3 (green triangles).
