1. Department of Space, Earth and Environment, Chalmers University of Technology, 412 96 Gothenburg, Sweden
2. School of Mathematics and Statistics, The Open University, Milton Keynes MK7 6AA, UK
3. The Center for Research and Invention, Veliky Novgorod 173008, Russia
4. Arctic and Antarctic Research Institute, Saint Petersburg 199397, Russia
5. Visual Computing Center, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia