Figure 1.
The distance that we measured at four levels is marked by arrows (A). The ‘Secure Window’ is painted with blue and the ‘Dangerous Triangle’ is outlined in red (B).
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.