MONITORING ROCK FALLS IN YOSEMITE VALLEY WITH THREE-DIMENSIONAL, HIGH-RESOLUTION PANORAMIC IMAGERY

Yosemite National Park experiences numerous rock falls each year, with over 600 rock-fall events documented since 1850. However, monitoring rock-fall activity has previously proved challenging due to a lack of high-resolution "basemap" imagery of the Valley walls. The Yosemite Extreme Panoramic Imaging Project, a partnership between the National Park Service and xRez Studio, has created an unprecedented image of Yosemite Valley's walls by utilizing gigapixel panoramic photography, LiDAR-based digital terrain modeling, and three-dimensional computer rendering. Photographic capture was accomplished by 20 separate teams shooting from key overlapping locations throughout Yosemite Valley. Photographs were taken simultaneously in order to ensure uniform lighting, with each team taking over 500 overlapping shots from each vantage point. Each team's photographs were then assembled into 20 gigapixel panoramas. In addition, all 20 gigapixel panoramas were projected onto a 1 meter resolution digital terrain model in three-dimensional rendering software, unifying Yosemite Valley's walls into a vertical orthographic view. The resulting image reveals the geologic complexity of Yosemite Valley in high resolution and represents one of the world's largest photographic captures of a single area. Several substantial rock falls have occurred since image capture, including large rock falls from Glacier Point in October 2008 and from near Half Dome in March 2009. Repeat photography of these areas clearly delineates the rock fall source areas, aids in volumes estimates, and informs the failure dynamics. In addition, smaller rock falls not previously documented have been discovered by comparing imagery. Thus, the panoramic gigapixel imagery has already proven to be a valuable tool for monitoring and quantifying rockfall in Yosemite Valley. It also sets a new benchmark for the quality of information a photographic image can provide for earth science study.