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.
Checkerboard pattern illustrating distortion at floor level (left) and 29-in. level (right). NOTE: Green marks are used as a visual aid to show the points selected for distortion analysis. The blue cross marks the center of the room. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).
