Yosemite Decimal System
DIFFICULTY RATING SYSTEM FOR ROCK CLIMBING ROUTES
Sierra Club grading system; Yosemite scale; Yosemite decimal system
The Yosemite Decimal System (YDS) is a three-part system used for rating the difficulty of walks, hikes, and climbs, primarily used by mountaineers in the United States and Canada. It was first devised by members of the Sierra Club in Southern California in the 1950s as a refinement of earlier systems, particularly those developed in Yosemite Valley, and quickly spread throughout North America.