Can iPad Pro be as reliable as TLS for urban forest inventories?

The labour cost and the time spent of experts are two main problems performing detailed urban forest (UF) inventories. So, different strategies have been adopted to reduce them while keeping or improving the data quality to generate information for urban planners and urban forest managers. These strategies can be a more sophisticated technique to get faster and precise information using Light Detection and Ranging (LiDAR) technology. The most used methods include airborne (ALS), terrestrial (TLS), and mobile laser scanning (MLS) to obtain dense 3D point clouds for the analysis of vegetation 3D structure (Tanhuanpää et al. 2014; Wężyk et al. 2016; Chen et al., 2019). Although methods based on LiDAR are more precise and faster for data acquisition, costs related may not be interesting for public administration because its costs are not related only to acquisition campaign but also to the costs of software for data processing and specialist (Ciesielski, Sterenczak, 2019; Li et al., 2019). For data acquisition at a tree level, one option to surpass the costs of a traditional laser scanner technology could be the use of mobile applications available for tablets or smartphones equipped with a scanner. The first mobile applications based on built-in laser scanner (LiDAR sensor) and image matching approach appeared in 2020 with the new model of iPad Pro 2020 and iPhone 12 Pro (iOS). The LiDAR sensor allows 3D precise scanning of objects located up to 5.0 m from the device and works by measuring the travel time of laser light photons sent from the device and reflected from the object (Narain, 2020). Our main goal was to test the applicability and preciseness of the iPad Pro 2020 to acquire data for tree DBH and distances compared to a traditional terrestrial laser scanner used in urban forest inventory.