Readings
Snavely, Seitz, Szeliski, Photo Tourism: Exploring
Photo Collections in 3D. SIGGRAPH 2006.
http://phototour.cs.washington.edu/Photo_Tourism.pdf
Supplementary reading:
   Szeliski and Kang. Recovering 3D shape and motion
from image streams using non-linear least squares.
J. Visual Communication and Image Representation,
1993.
http://hpl.hp.com/techreports/Compaq-DEC/CRL-93-3.pdf