Sea Ice Thickness Measurement from an Ice Breaker Using a Stereo Imaging System Consisted of a Pairs of High Definition Video Cameras

Sea ice monitoring is quite important from the global warming point of view. Sea ice thickness is one of the most important parameters for understanding the heat flux of sea ice area. Usually, sea ice thickness is measured by drilling a hole on the sea ice. However, this work does take a lot of time. In order to effectively measure sea ice thickness from an icebreaker deck, in 2000, the authors have introduced a 3D measurement system using a pair of digital cameras. When the icebreaker breaks sea ice, the crosssection of the sea ice comes above sea level, and can be captured by the cameras. The system allows users to measure sea ice thickness with the error of 1.5cm when the stereo pair images were taken from the 2.5m above the sea level in proper condition. However, since the broken sea ice is moving rapidly, catching of good timing to release the shutter was not easy. As a result, number of the good stereo pair images was always limited compared with the total number of images taken during one cruising. Recently, the authors have replaced the digital cameras with high definition video (HDV) cameras. SANYO Xacti DMX-HD 1000 was selected as the HDV video cameras. Since the video cameras can continuously take the sea ice movement, the best stereo pair images to measure the sea ice thickness can be selected after the observation. In March 2009 and 2010, the authors have performed several experiments on an icebreaker Garinko-2 around the Monbetsu Bay of Hokkaido, Japan. The total number of the good stereo pair images taken during one cruising increased two or three times compared with the previous system. The result proved the usefulness of the system for measuring sea ice thickness along the trajectory of the ice breaker without stopping the cruising. .