Measurement of Tree Height and DBH in Urban Areas Using RTK-Enabled Smartphones

Accurate, rapid, and cost-effective measurement of biometric parameters such as diameter at breast height (DBH) and tree height is crucial for urban forestry inventories. While traditional field methods and mobile LiDAR systems offer high accuracy, their cost often limits accessibility. This study explores the applicability of real-time kinematic (RTK)-enabled smartphones as an alternative for urban tree inventory measurements. Data collected with an iPhone 14 Pro in Selçuklu, Konya, Turkey, were compared against high-accuracy reference point cloud data from a Riegl VMX mobile LiDAR system. To improve positional accuracy, an ArduSimple handheld GNSS receiver integrated with the TUSAGA-Aktif CORS-TR network was employed, and a structure-frommotion workflow was used to process smartphone imagery. The results demonstrate that RTK-enabled smartphones can achieve strong agreement with LiDAR-based measurements, supported by high correlation coefficients for both DBH and tree height. These findings suggest that smartphones, when combined with RTK corrections, provide a practical, economical, and reliable alternative for urban tree inventories, though limitations remain in small-diameter tree measurements due to error margins of approximately ±10 cm.