Tree Measurements in the Urban Environment: Insights from Traditional and Digital Field Instruments to Smartphone Applications

Urban forests can provide essential environmental and social functions if properly planned and managed. Tree inventories and measurements are a critical part of assessing and monitoring the size, growth, and health condition of urban trees. In this context, the parameters usually collected are diameter at breast height (DBH) and total height, but additional data about crown dimensions (width, length, and crown projection) are required for a comprehensive tree assessment. These data are generally collected by urban foresters through field surveys using tree calipers or diameter tape for DBH and the electronic ipsometer/clinometer to measure tree height and crown size. Greater detail could be achieved using a digital instrument such as Field-Map, a portable computer station, to quickly realize dimensional and topographic surveys of trees and forest stands. Additionally, the incorporation of a LIDAR scanner into a smartphone such as the iPhone 12 Pro has made this device able to measure tree attributes as well as additional spatial data in the field. In this study, we tested these 3 different measurement systems in a field sampling of an urban forest and compared them in terms of measurable parameters, accuracy, cost, and time efficiency. Furthermore, we discussed the pros and cons of each measurement approach and how the resulted data can be used to evaluate ecosystem services of trees and provide guidance on tree management in order to reduce potential risks or disservices.