It is possible that processing a contribution may fail. In this case, several sources of errors should be considered:

• The video is not a tree video
• The 3D reconstruction of the tree from the video failed because:
• The video resolution is too low
• The video is too blurry because the focus is bad
• The video is too blurry because the user moved too quickly
• The tree was moving too much (wind for example)
• ...
• The automatic measurement of the tree failed because:
• The 3D reconstruction of the tree was not accurate enough
• The trunk was not visible
• ...