Accuracy of Aerial Photography for Locating Seasonal (Vernal) Pools in Massachusetts
Several studies in the northeastern U.S. used aerial photographs to map potential seasonal (vernal) pools, yet their accuracy is highly variable. We used the statewide seasonal pool database and two other independent aerial photographic seasonal pool surveys in conjunction with field surveys to assess the accuracy of aerial photography for locating seasonal pools at four study sites in central and western Massachusetts, and compared the overlap of mapped pools for each aerial photographic survey database. Commission errors ranged from 0% to 50% for meeting the physical criteria, and 4% to 61% for meeting the biological criteria for certification. There was low overlap (16% to 33%) between databases for potential seasonal pools mapped, and digitizing errors ranged from 13% to 65% of assessed pools, typically between 1–31 m. Photo type, scale, quality of the imagery, forest cover, spring precipitation levels, and minimum mapping unit can all affect the ability of a photo-interpreter to accurately map potential seasonal pools. Despite these limitations, aerial photographic surveys provide an important tool for locating seasonal pools over large areas; however, substantial numbers of seasonal pools may be missed by these surveys.