The U.S. Department of Homeland Security (DHS) has the responsibility to protect and control U.S. borders against terrorist threats, criminal endeavors, illegal immigration, and contraband. Unfortunately, due to budgetary and other resource constraints, DHS cannot see and be everywhere at once along America's long and porous border. As a result, DHS officials continually face the question of where, when, and how to position people and technology on the border. Confronting ...