Forest Inventory by Means of Tree-wise 3d-measurements of Laser Scanning Data and Digital Aerial Photographs

Two of the most promising new remote sensing technologies for increasing accuracy and efficiency of forest inventory are tree-wise or stand-wise measurements of airborne laser scanner data or 2(2D) and 3-dimensional measurements (3D) of digital aerial photographs. The aim of the study was to compare 3D measurements of digital aerial photographs and laser scanning to 2D measurements of digital aerial photographs and traditional compartment-wise inventory. Comparison was based on the expected net present value (NPV) losses. Reference data was measured from Central Park of Helsinki, Finland. The results showed without inventory costs there was not any significant difference between the expected NPV losses of 3D measurements of digital aerial photographs and laser scanning and compartment-wise inventory method. Due to the small size of study area (700 ha) the costs of remote sensing techniques increased considerably and compartment-wise inventory method was the most cost-effective when accounting for inventory costs. However, if the inventory area had been over 20 km, the expected NPV losses of 3D and compartment-wise inventory methods would have been similar. Also in 2D method the costs decrease with respect to the size of the area. When accounting NPV losses 3D and compartment-wise methods produce always better results than 2D method due to better accuracies.