Counting trees - methods of automatic analysis of photogrammetric data in forests of the continental region

The paper is devoted to the methods of automatic analysis of photogrammetric data in forests of the continental region. It also discusses how automatic tree counting can be used to manage forests. Experimental research was conducted to verify two methods: Faster R-CNN and Template Matching to automatically detecting tree objects in the continental region characterized by mixed forests with a large predominance of conifers. The research was done based on photogrammetric data taken in four areas belonging to forest districts subordinate to the Regional Directorate of State Forests in Zielona Góra. Data was collected from drones and small airplanes with a photogrammetric container. The results show that both methods can be used for analyzes in specific cases. Moreover, the level of Recall shows the advantage of Faster R-CNN methods for the photogrammetric data collected during the flights in various weather conditions.

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

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.