USGS employee uses the alignment of mountains.

After hiking to the location of the historic photo, USGS employee, Lisa McKeon, uses the alignment of mountains and permanent features to compose the same shot as the original.  Sometimes, determining the location can take a long time, requiring moving up and down a mountainside to find the exact spot. Many of the locations are just a day hike, but others require multiple back-county nights to access the historic photo point.