Tim K. Marks Andrew Howard Max Bajracharya Garrison W. Cottrell Larry H. Matthies Gamma-SLAM: Visual SLAM in unstructured environments using variance grid maps. 26-51 2009 26 J. Field Robotics 1 http://dx.doi.org/10.1002/rob.20273 db/journals/jfr/jfr26.html#MarksHBCM09