URBAN TREE CROWN PROJECTION AREA MAPPING WITH OBJECT BASED IMAGE ANALYSIS FOR URBAN ECOSYSTEM SERVICE INDICATOR DEVELOPMENT
TAKÁCS ÁGNES, TANÁCS ESZTER, KISS M., GULYÁS ÁGNES
ABSTRACT. Urban tree crown projection area mapping with object based image analysis for urban ecosystem service indicator development. The continuous expansion of built-up areas in the urban environment at the expense of green spaces brings up numerous environmental problems, for which accurate and efficient solutions should be found. The assessment of ecosystem services developed within the field of landscape ecology is playing an ever more important role in environmental sciences and thus may offer suitable answers. Such assessments can be carried out by developing indicators. Accordingly, in the case of urban trees, an accurate quantitative characterization of their services (such as e.g. carbon sequestration, pollutant removal and microclimate regulation) is also needed. The aim of this study is to establish a generally applicable method based on indicator development, using widely available data. In the case of urban green spaces there are several services for which the development of proper indicators and evaluation methods requires a delineation of tree crowns, or at least the crown projection area. Accordingly, in our work, we map the crown projection area of a large and popular urban park of Szeged, Széchenyi square, using object-based image analysis on UltraCamD digital orthophotos. Following a multiresolution segmentation the classification of the resulting objects was carried out, using the eCognition image analysis software. Besides fulfilling the policy objectives related to the evaluation of urban ecosystem services, the produced crown base can also be used in several other types of urban ecological and urban climatological studies (e.g. urban climate modelling, human-comfort assessment). In this paper the first results are presented.
Keywords: ecosystem services, crown projection area, eCognition, object-based analysis