Mapping and measuring buildings in the canopy boundary layer in ten U.S. cities

Abstract

This study reports on development of a method for inventorying characteristics of urban buildings with special emphasis on their surface construction materials. The work was conducted in response to stated needs from scientists engaged in acid rain damage studies, urban meteorologists interested in the condition of the canopy boundary layer of cities, and others involved in investigations of the physical character of the urban environment. In several instances, these scientists have had little choice but to derive physical (or morphological) characteristics of the city from available spatial data on featuring functional (rather than physical) aspects. The method developed, applicable globally, could support urban meteorological studies. The cities examined were: Boston, Philadelphia, Baltimore, Pittsburgh, Cincinnati, Atlanta, Houston, Denver, Seattle, and Sacramento. All exhibit a wide variety of urban landscapes, building types, and construction materials. High altitude color infrared aerial photographs (at Ames Research Center) were employed to delimit urban terrain zones prior to visiting each city for making direct observations and measurements. Criteria for zone delimitation are morphological and consist of building construction type, venting characteristics, age, density, and related street patterns, items recorded in the field survey were: building dimensions, height, type of roof, venting, and building surface material (e.g., stone, brick, concrete, wood). The data — aggregated by urban terrain zone — reveal, for example, that wall and roof surfaces in areas of tall, densely spaced buildings exceed the ground surface. Conversely, wall and roof areas of low density single-family detached houses form only a small proportion of the ground surface area. These three-dimensional data provide a far more detailed view of the canopy boundary layer in cities than is possible using two-dimensional surface measurements alone. Data analysis also reveals that many of the urban terrain zones (especially those in commercial and industrial areas) are remarkably similar regardless of the city's location. As expected, the dominance of local building materials is more important in houses and other small buildings.