Scene change detection for vision-based topological mapping and localization

A method for detecting changes in the environment using only vision sensors is presented. We demonstrate that optical flow can be used to detect these changes at key locations in outdoor scenarios in difficult and varying lighting conditions. These key locations are used as nodes in a topological mapping and localization framework. To close the loop we employ a bag-of-words methodology. We show that bag-of-words methods can be used in real-time on a standard computer to detect loop closures in sparse topological maps. Experimental results from field trials using our quad-rotor UAV demonstrate the capability of the proposed scene change detection method.