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 inset graphics show the three methods of error measurement. The filled circle shows the target, dots show example endpoints of footprint centroids, and the open circle shows the mean endpoint position. Dashed lines show fast steps, continuous lines show slow steps.
