Lance Cpl. Joshua Byer, left, and Lance Cpl. Justin Goodchild use a Defense Advanced GPS Receiver to check a heading during a land navigation test at Marine Corps Air Station Cherry Point, N.C., Sept. 3, 2014. Byer and Goodchild are both gunners with 2nd Low Altitude Air Defense Battalion, practicing their land navigation skills during team leaders course. Byer is a native of Columbus, Ohio and Goodchild is a native of Longwood, Fla. - Lance Cpl. Joshua Byer, left, and Lance Cpl. Justin Goodchild use a Defense Advanced GPS Receiver to check a heading during a land navigation test at Marine Corps Air Station Cherry Point, N.C., Sept. 3, 2014. Byer and Goodchild are both gunners with 2nd Low Altitude Air Defense Battalion, practicing their land navigation skills during team leaders course. Byer is a native of Columbus, Ohio and Goodchild is a native of Longwood, Fla.