Development of GNSS Buoy for a Synthetic Geohazard Monitoring System
Teruyuki Kato*1,†, Yukihiro Terada*2, Keiichi Tadokoro*3, Natsuki Kinugasa*3, Akira Futamura*4, Morio Toyoshima*5, Shin-ichi Yamamoto*5, Mamoru Ishii*6, Takuya Tsugawa*6, Michi Nishioka*6, Kenichi Takizawa*7, Yoshinori Shoji*8, and Hiromu Seko*8
*1Earthquake Research Institute, The University of Tokyo
1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
*2National Institute of Technology, Kochi College, Kochi, Japan
*3Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan
*4National Institute of Technology, Yuge College, Ehime, Japan
*5Wireless Networks Research Center, National Institute of Information and Communications Technology, Tokyo, Japan
*6Applied Electromagnetic Research Institute, National Institute of Information and Communications Technology, Tokyo, Japan
*7Resilient ICT Research Center, National Institute of Information and Communications Technology, Tokyo, Japan
*8Meteorological Research Institute, Japan Meteorological Agency, Tokyo, Japan
The GNSS buoy system for early tsunami warnings has been under development for about 20 years. A small prototype buoy was first deployed in Sagami Bay, Japan, in 1997. Then, after a series of experiments aiming for operational use, the system was implemented as a part of national wave monitoring system NOWPHAS. The NOWPHAS system had set up more than 10 GNSS buoys around Japan by 2011, and it recorded the tsunami caused by the 11 March 2011 Tohoku-oki earthquake. The records were used to update the tsunami warning at the time of the 2011 Tohoku-oki earthquake. However, the buoys were placed less than 20 km from the coast, as the system used the baseline mode RTK-GPS algorithm, which was not far enough for effective evacuation of people. Thus, we began trying to improve the system by putting the buoys much farther from the coast. The new system employs a newly developed positioning algorithm, Precise Point Positioning with Ambiguity Resolution (PPP-AR), together with satellite data transmission. A series of experiments involving the new system successfully indicated changes in sea level with an accuracy of a few centimeters. Given the success of the experiments, we are trying to use the GNSS buoys not only to provide early tsunami warnings but also to monitor various other geohazards. For example, we are trying to use the GNSS-Acoustic system to continuously monitor crustal movements on the ocean floor, to monitor the ionosphere, and to monitor the atmosphere. Ancillary sensors on the buoys will be utilized for oceanographic monitoring as well.
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