Electronic Field Guide Created in iPhone App

(Leafsnap, iTunes Store)

Columbia University in New York, the University of Maryland in College Park, and the Smithsonian Institution in Washington, D.C. have created a tree identification guide called Leafsnap that operates as a smartphone app. The guide is available free of charge for the Apple iPhone; Android and iPad versions are planned for later this year.

This electronic field guide allows users to identify tree species simply by taking a photograph of the tree’s leaves with the iPhone’s camera. The guide’s software then uses a visual search/recognition algorithm to match the leaves to its database.

Leafsnap returns the species name, as well as high-resolution photographs and information about the tree’s flowers, fruit, seeds and bark. Currently, Leafsnap’s database includes the trees of the northeastern U.S., but it will soon expand to cover the trees of the entire continental United States.

Columbia computer scientist Peter Belhumeur told the university’s magazine The Record last month that a leaf’s shape is its least variable feature and easiest to capture in a photo. Thus, the team focused on characteristics like smooth versus jagged, many-lobed or single-lobed. They then wrote a search and evaluation routine to rank the images by most- to least-similar, and eliminate the images least similar.

Users of Leafsnap  will also be contributing their discoveries to the larger scientific community. As people use Leafsnap, the app will automatically share their images, species identifications, and the tree’s location with other scientists. These scientists will then use the information to map and monitor population growth and decline of trees nationwide.

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