Yosemite National Park Ranger Scott Gediman says new data prompted the closing of 18 canvas- and wood-sided cabins, as well as two dorms that house 30 employees. All are located in the park's popular Curry Village. 

GEDIMAN: "Yosemite National Park hired a company to basically fly an airplane across Yosemite Valley, and literally thousands of high-resolution photographs were taken of the cliff walls."

The laser photographs helped them develop a more accurate picture of rockfall patterns from the valley's iconic 3,000-foot granite walls.  Gediman says the permanent cabin closures will significantly reduce risk to visitors.  He says the park will not be closing any trails or visitor areas.

Park managers had already closed about one-third of the housing in Yosemite's Curry village in 2008, after a serious rock fall injured some visitors and damaged some cabins.