Digital horizontal tree measurements for forest inventory

Scots pine tapering and stem volume estimation was tested by photographing single pine stems in normal Boreal forest conditions with a simple digital camera. In the volume estimation a new methodology was developed where a tapering model was used to supervise the image interpretation. The results were compared with traditional methods by felling and manually measuring the test trees on the ground. The developed method resulted in a -0.6mm - -2.8 mm bias and 7.0 mm - 9.4 mm RMSE in diameter estimates and 0.4 % bias and 7.3 % RMSE in volume estimates. The achieved accuracies of the diameter and volume measurements were at comparable levels with traditional volume estimates based on measurements of height and one or two diameters. This level of accuracy was considered satisfactory. However, the variation in the photographing conditions and the performance of the simple digital camera did not always produce the required image quality for further analysis.