1. Department of Mechanical and Industrial Engineering, University of Toronto, ON M5S 3G8, Canada. E-mails: bahar@cs.toronto.edu, cchui@mie.utoronto.ca, gruninger@mie.utoronto.ca, yi.ru@mail.utoronto.ca
2. National Center for Geographic Information and Analysis, School of Computing and Information Science, University of Maine, Orono, ME 04469, USA. E-mail: torsten@spatial.maine.edu