Volume measurement of wood disks

Abstract: At the Department of Forest Products at Swedish University of Agricultural Sciences different metrics for wood are used. The volume of wood disks' is measured using archimedes principle.There are concerns of how accurate this measurement is and a different measuringsystem is wanted. This thesis has investigated the possibility of measuring the disks' volumes with imageanalysis. The recovery error should be less than 1% of the actual volume. In general, there are two methods for recovering an object using imageanalysis, active and passive methods. Compairing active and passive methods, active methods usually require simple algorithms but more expensive equipment compared to passive methods. Different methods for measuring objects' volumes have been evaluated and the choosen method was ``shape from silhouette''. Shape from silhouette is a passive method, only using the silhouette of anobject from multiple views to recover the objects volume. Passive methods have one drawback, they can only recover the visual hull of an object and the wood disks can be slightly concave. Due to the questionable accuracy of the current measurement method it was still deemed as possible to achieve at least equal performance. When the volume measuring algorithm was developed it was first tested in two simulations using on a sphere to determine its performance with different voxel sizes and different number of images. The algorithm performed well and an error of less than 1 % was achieved with a sphere. A third simulation was performed using a simulated wood disk, which is a much more complex object, and 5 % accuracy was achieved. Finally, an experiment on real images was performed. This experiment did, however, fail due to the low quality imaging setup. The conclusion of this thesis is that itis not possible to achieve less than 1 % accuracy of the recovered volume using the shape from silhouette technique.