Mapping Urban Land and Tree Cover
Trees are an important component of urban environments. In addition to their aesthetic value, trees have significant economic and environmental benefits, including: reducing stormwater runoff, energy conservation, improving air quality, and enhancement of community vitality, stability and property values for residential and business areas. An urban tree cover (UTC) assessment that estimates the amount of tree canopy currently present, along with the amount of tree canopy that could potentially be established, is the first step in the UTC goal-setting process. Accurate maps and information on the amount of tree and forest cover is not routinely available, and would be expensive to acquire by field mapping methods. Analysis and classification of remote sensing imagery, along with geographic information system (GIS) analysis and modeling, provide the most efficient method for assessment.
The RSGAL has classified and mapped the land and tree cover for the cities of Minneapolis, Saint Paul, and Woodbury using Quickbird satellite imagery and lidar point cloud data. The approach used a combination of high resolution (0.6 meter) multispectral imagery and lidar data and object-based image analysis. Classification accuracies were greater than 90 percent. The percent tree canopy cover in the three cities was: Minneapolis 31.5, St. Paul 32.5 and Woodbury 21.5. The classification results can be downloaded from portal.gis.umn.edu.