From PanoTools.org Wiki
Revision as of 22:15, 13 January 2012 by Erik Krause (same look as "pitch")
Roll is the angle of camera rotation around it's optical axis and part of the panotools Image positioning model.
If your camera is not level this can be in two directions:
- the image is tilted up or down, resulting in a Pitch value different from 0.0
- the image is rotated such that the horizon is not horizontal if held upright, resulting in a Roll value different from 0.0