Accuracy in estimating basal areas for forest inventories: comparison of Android-based virtual relascope and Spiegel Relaskop

Abstract

The potential for using smartphones extends to forest inventory. Several applications allow the estimation of basal areas, transforming the device into a low-cost virtual relascope. The accuracy of the Bitterlich relascope application was analyzed using four low-performance devices. The results were compared with those of a Spiegel Relaskop. The measurements were taken with artificial targets; this increased the discrimination of the results in comparison with tests made by counting trees. To check the accuracy in real field conditions, the Bitterlich relascope application was compared with a Spiegel Relaskop. No significant differences in accuracy were found between the data obtained by the traditional relascope and that obtained by the Android devices, neither for the artificial target nor in field conditions. The obtained biases were also similar between the Spiegel Relaskop and the devices tested. To achieve high-quality measurements with the smartphones, a realistic calibration resembling forest inventory is needed.