Merrill, Robert H., 1881-1955, “Ladder & grids at Grand Rapids,” Digital Collections, accessed March 31, 2025, https://digitalcollections.library.gvsu.edu/document/50425.
Black and white photograph of a ladder with two adjustable legs over a measuring grid square on grass. Part of a camera ladder rig system developed by Merrill for taking overhead photographs of archaeological excavations. Flowers and trees are visible behind the ladder.