Development of regular check-up system of slope stability using RTK-GPS

GPS已经实现了地面上哪怕是一颗钉子的高精度测量。实时动态(RTK)-GPS可以在更短的时间内测量更多的点，而不是传统的静态GPS。RTK-GPS通过监测滑坡前兆运动，实现了“滑坡稳定性定期检查系统”。为利用RTK-GPS开发该系统进行了基础性研究，取得了以下成果。通过定点24小时连续监测，检验RTK-GPS定位的稳定性。水平定位标准差为3 mm。没有观察到漂移和跳跃。进行了通电/关机试验，但得到的第一个位置分散不超过1厘米。这些结果表明RTK-GPS定位具有很高的稳定性。静态GPS定位精度小于5 mm需要2个多小时，而RTK-GPS 1秒监测在5分钟内定位300个历元，南北和东西方向的标准偏差仅为3 mm左右，上下分量的标准偏差约为6 mm。这一结果表明RTK-GPS具有足够的检测5 mm运动的能力。在研究期间，对高知县五塔滑坡进行了短期RTK-GPS测量。结果表明：(1)在5分钟内300个历元，即使在斜坡上，标准差也只有3 mm。(2)五塔滑坡测点在不同滑块中的运动向量表现出不同的运动方向。这说明RTK-GPS可以用于滑坡块体识别。利用电子测斜仪和伺服电机研制了GPS天线三脚架自动稳定器。它可以辅助RTK-GPS短时测量，因为它可以帮助将天线设置在地面上测量钉子的正上方，并在测量期间将天线保持在1 mm以内，即使在软弱地基上也是如此。该系统通过关西TLO向日本专利局申请专利。

GPS have realized high precision survey of even a single nail on the ground. Real-Time Kinematic (RTK)-GPS can survey more points in shorter period than conventional static GPS. RTK-GPS could realize "regular check-up system of slope stability" system by detecting landslide precursor movement. Fundamental research was conducted for developing the system using RTK-GPS and obtained following results.1. Stability of RTK-GPS positioning was examined by 24-hrs continuous monitoring at a fixed point. Standard deviation of horizontal positioning was 3 mm. No drifting nor jump was observed. Power on/off test was conducted, however obtained first position dispersed not wider than 1 cm. These results imply high stability of RTK-GPS positioning. Static GPS needs more than 2 hours for positioning a point with precision of smaller than 5 mm, however, 300 epochs in 5 minutes by RTK-GPS 1-second-monitoring show standard deviation of only about 3 mm in North-South and East-West and about 6 mm in Up-Down component. This result means RTK-GPS has enough capability of detecting 5 mm of movement.2. Short-time RTK-GPS survey was repeated in Nuta landslide, Kochi Prefecture over the research period. Results show ; (1) 300 epochs in 5 minutes show only 3 mm of standard deviation even on slopes. (2) Movement vectors of the survey points in Nuta landslide in different landslide blocks show different movement direction. This implies that RTK-GPS can be used for landslide block discrimination.3. Automatic GPS antenna tripod stabilizer was developed using a electronic inclinometer and servo-motor. It can assist RTK-GPS short time survey because it can help setting the antenna exactly above the survey nail on the ground in a minute and keep it within 1 mm during the survey time even on soft ground. This system was applied for patent through Kansai TLO to the Japanese Patent Office.