Development of a tsunami detection system using RTK-GPS

我们开发了一个使用RTK-GPS技术的海啸探测系统。RTK-GPS是一种采用全球定位系统的移动平台实时定位系统。首先，我们设计了一个浮标系统，由两个浮标组成；8米长的桅杆式浮标，用于放置GPS天线和支撑浮标，用于放置GPS接收器、PC机、电池等。这些浮标是用一根电缆拴在一起的。我们在关东南部的相模湾进行了实验。两个浮标都停泊在离海岸约900米的地方，数据通过无线电传输。浮标的供电采用太阳能电池板和风力发电机的混合动力系统。数据传输到地面后，RTK处理后的数据在实验室设置的PC机显示器上进行监控。数据连续记录了大约10天，没有一秒的丢失。所取得的资料与放置在附近的验潮仪记录作了比较。比较表明，估计的海平面有大约1厘米的精度。然后，为了检查长期稳定性和检查环境稳健性，我们在大阪湾进行了大约一年的实验。对获得的数据进行频率分析表明，风波的影响在不到几秒的范围内是优越的，而通过滤波技术可以探测到较长时间的海啸。因此，实验是成功的，所提出的浮标系统可以在海啸到达海岸之前检测到海啸的到来，可以用于海啸预警。第二代海啸浮标目前正在大船渡近海运行，用于当地政府监测海啸。

We have developed a tsunami detection system using RTK-GPS technology. RTK-GPS is a real-time positioning system of moving platform using the Global Positioning System. First, we designed a buoy system that consists of two buoys; a spar type buoy of 8m long for putting a GPS antenna and a support buoy for putting GPS receivers, PC, butteries etc. These buoys are tethered using a single cable. We have conducted an experiment at the Sagami Bay, southern Kanto. Both of buoys were anchored about 900m offshore of the coast and the data were transmitted using radio. Hybrid system using solar panels and a wind generator was used for power supply on the buoy. After the transmission of data to land, the RTK processed data were monitored on the display of a PC that was set in the laboratory. The data was recorded continuously for about ten days without a single second of loss. The obtained data were compared with the tide gauge records placed nearby. The comparison suggested that the estimated sea-level has about 1cm accuracy. Then, in order to check the long-term stability and to examine the environmental robustness, we have conducted about one year of experiment in the Osaka bay. Frequency analysis of obtained data suggested that the effects of wind waves is superior in the range of less than several seconds and the longer period of tsunami could be detected by filtering technique. Thus, as a conclusion, the experiment was successful and the proposed buoy system may be utilized for tsunami warning because it can detect the arrival of tsunami before it reaches the coast. The second generation of tsunami-buoy is now operation offshore of Ofunato for monitoring at local government for watch tsunami.