engleski

Testing applicability of MOTI smartphone application for measuring tree height

Measurement of tree attributes is the basis of a forest inventory, and many specialized instruments are designed for this purpose. The development of mobile phone technology enabled new possibilities for various applications in field practice. One such smartphone application is MOTI that is freely available on the internet. It is dendrometric measurement tool designed for collection of field data such as tree height, basal area and the number of trees. In order to check its applicability in field conditions, it was compared to Vertex hypsometer for measurement of tree height. MOTI was used for measurement in the controlled conditions (known height on city building) and forest stand (tree height of 76 beech and fir trees). Data were tested by paired t-test and height curves compared. Individual heights measured by MOTI differ from Vertex: on a city building average difference was +1, 5 m (absolute values ranging from 0, 1 to 16, 7 m), with 49% data differing less than ±2 m. In stand conditions, MOTI heights were on average -0, 9 m lower than Vertex (absolute values ranging from 0 to maximum 10, 5 m), with 47% values in range less than ±2 m. Testing height differences showed statistical significance on 0, 05 level for controlled heights (p=0, 03), and beech trees (p=0, 003), but not for fir (p=0, 08). Height differences (in absolute value) are statistically significantly correlated with tree height (r=0, 27, p=0, 01). There is also correlation of height differences and distance, especially for beech (r=0, 45) which could be attributed to crown shape and surveyor. Height curves (regression models) based on MOTI data showed lesser determination coefficients compared to Vertex data (0, 84 to 0, 92 for fir and 0, 75 to 0, 82 for beech). MOTI height curve for fir showed little difference from Vertex (decreasing with dbh), while beech curve was constantly lower compared to Vertex and increased with dbh. Since individual tree height data from MOTI considerably differ from the reference values and have a high variability, repeated measurements are necessary to improve the results. According to the results, tree height measurement from 10 to 30 m distance is suggested. Application has not proven reliable for measurement of individual trees, while it could be used for larger samples and height curves. Applicability of MOTI possibly depends on the mobile device used (screen resolution, inclinometer precision…), but it should be further checked. Overall impression is that MOTI still needs improvements and further field checks in order to make its simplicity and free availability work efficient.

forest inventory, MOTI, smartphone, tree height, Vertex

nije evidentirano