Hajime Nagahara Atsushi Ichikawa Masahiko Yachida Depth estimation from the color drift of a route panorama. 4066-4071 2008 IROS http://dx.doi.org/10.1109/IROS.2008.4651016 conf/iros/2008 db/conf/iros/iros2008.html#NagaharaIY08