Fig. 1.

Overall approach. (a) Signs provide absolute location estimates. Images of an Exit sign (cropped for visibility) taken from three locations are shown on the right, with dashed arrows to corresponding red dots showing approximate location of camera inferred from each image. (b) Prototype system tested in this work uses barcode-like marker patterns, shown here, affixed to the corridor walls instead of Exit signs; we will use Exit signs and other existing signs in place of markers in the future. (c) Map of indoor environment used in our experiments shows sample trajectories estimated along routes R1 (green) and R2 (red).