A Comparison of Three Methods for Measuring Local Urban Tree Canopy Cover

By Kristen L. King and Dexter H. Locke

New York (March 4, 2013) – Measurements of urban tree canopy cover are crucial for managing urban forests and required for the quantification of the benefits provided by trees. These types of data are increasingly used to secure funding and justify large-scale planting programs in urban areas. Comparisons of tree canopy measurement methods have been conducted before, but a rapidly evolving set of new technologies and applications may leave urban foresters wondering, “Which method is most appropriate for my circumstances?”

This analysis compares two well-established measures of local tree canopy and building cover with a third, relatively untested technique. Field-based visual estimations (using the USDA Forest Service’s i-Tree protocols), summaries of high-resolution land cover data using geographic information systems (GIS), and an analysis of skyward-oriented hemispherical photographs at 215 roadside sites across the five diverse counties of New York City, New York, U.S., are the methods evaluated.

The study authors found no statistically significant differences between the methods when comparing tree canopy; however, the hemispherical camera had a tendency to overestimate building coverage. It is concluded that hemispheric photo techniques are understudied in urban areas, and that the i-Tree and GIS-based approaches are complementary and reinforcing tools indispensable for both the urban forest management and research communities.

Source:
A comparison of three methods for measuring local urban tree canopy cover, Arboriculture & Urban Forestry. 39(2): 62-67.