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.
Directional features f3 and f4 for frames from the simulation experiment. Each marker corresponds to one frame. Different markers indicate different backgrounds: asterisk - black, circle - city, cross - tree, diamond -valley, and square - sky. The separation line L best separates the two clusters according to Eq. (25).
