Evaluation of smartphone applications for measuring the total height of trees

Portuguese. The objective of this study was to evaluate the precision and accuracy of smartphone applications for measuring the total height of trees. We measured the heights of 90 trees of different species on the campus of the Federal Rural University of Rio de Janeiro in Seropédica, equally distributed in three height classes: (1) h ≤ 11.5 m; (2) 11.5 <h < 20 m; and (3) h ≥ 20 m. The heights measured by the Vertex III® hypsometer was the reference for the comparison of the tested applications: Measure Height (MH and MDH), Hypsometer (HYP), Simple Measure (SM), Height Calculator (HC), Smart Tools (ST), Height and Distance (HD), Two Point Height (TPH and TPH2) and Tree Meter (TM) using the MOTO G5 smartphone. For data analysis, we performed an F (α = 0,05) test, and if there is a significant difference Dunnett's mean test (α = 0,05) was applied, and height variation coefficients (CV%) were analyzed for all applications used. Then, we carried out the graphical analysis of the differences and the statistical parameters of Bias (V), Mean of Absolute Differences (MD), Standard Deviation of Differences (DPD), ending with the performance index (c). We concluded that the applications Height Calculator (HC), Smart Tools (ST) and, Two Point Height, (TPH) present greater precision and accuracy in the measurement of the total height of the trees. However, we observed that increasing the height of the trees, reduces the performance of the applications, mainly using the Simple Measure (SM) and Height and Distance (HD) applications. The Tree Meter (TM) can be used on trees smaller than 20 m in total height. Measure Height (MH and MDH) and Hypsometer (HYP) applications have low precision and accuracy in estimates.