Review of Urban Tree Inventory Methods Used to Collect Data at Single-Tree Level

With a growing number of urban tree inventory methods and diversifying use of tree inventory data by city authorities and researchers, there is a need to evaluate, review, and critically assess the inventory methods available. This study reviewed studies using urban tree inventories at single-tree level as their data source. Based on this, a bibliographic overview was established and a typology of contemporary urban tree inventory methods was created and used as a framework for evaluation and discussion of the measurement type and accuracy achievable with different methods. The authors found that data from urban tree inventories are currently being employed in research with an increasing number of focuses across a geographical scope that spans all continents except Africa. Four main types of urban tree inventories were distinguished: satellite-supported methods, airplane-supported methods, on-the-ground scanning or digital photography, and field surveys. Compiling results across studies and evaluating the parameters collected by these inventory methods and their accuracy of measurement revealed that the technology itself and current data processing methods limit the reliability of the data obtained from all methods except field surveys. The study authors recommend further technological development and scientific testing before these methods can replace field surveys.