The use of Global Positioning System techniques for the continuous monitoring of landslides: application to the Super-Sauze earthflow (Alpes-de-Haute-Provence, France)
The use of Global Positioning System techniques for the continuous monitoring of landslides: application to the Super-Sauze earthflow (Alpes-de-Haute-Provence, France)
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DOI：
10.1016/s0169-555x(01)00098-8
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发表时间：
2002-02-01
期刊：
影响因子：
3.9
通讯作者：
Calais, E
中科院分区：
文献类型：
--
作者：
Malet, JP;Maquaire, O;Calais, E
近期研究表明，全球定位系统（GPS）技术可用于精确确定自然灾害领域中移动点的三维坐标。实际上，对滑坡运动的详细分析，特别是对于近实时预警系统而言，需要三维（亚厘米级）的精确定位和精细的时间分辨率（每小时或更短时间）相结合。利用GPS对滑坡进行监测通常采用重复测量的方式，作为对传统大地测量方法的补充。利用GPS对滑坡进行连续监测在实际操作中通常不进行，主要是因为与传统变形监测技术相比，这种系统成本较高。此外，如果GPS测量在长时间观测（通常为24小时）中能够达到毫米级精度，其精度会随着观测时长的增加而降低，这是因为卫星星座的变化以及观测地点的多路径效应所引入的误差。本研究旨在确定利用GPS对滑坡进行连续监测时GPS测量的实验精度。特别是，我们希望根据观测时长来校准测量精度的变化。该研究在法国南阿尔卑斯山的苏佩 - 索兹（Super - Sauze）泥石流上进行，该泥石流呈渠化流动，表面位移每年可达几十厘米到几米。1999年5月和10月的两次测量活动中获取了GPS数据（在泥石流外设置了两个参考站，在泥石流上分布了四个“移动”站）。1999年5月的三周内，最大三维累积位移达到2.1米。1小时观测时段内，南北向、东西向和垂直向分量的精度分别达到2.7毫米、2.2毫米和5.0毫米。在平面测量中，对于显著运动和给定时间分辨率的可检测阈值介于3.5毫米/24小时和8.5毫米/小时之间，在高程测量中介于6毫米/24小时和19.5毫米/小时之间。因此，GPS测量能够清晰地检测到泥石流的运动，并且将结果与传统大地测量方法（经纬仪和电子测距仪）或钢丝引伸计装置所获得的结果进行了比较。此外，定期地形测量、连续引伸测量和GPS测量相结合，使我们能够识别泥石流表面速度的季节性和偶发性瞬时变化。对降雨（降雪）、地下水位和位移之间关系的分析，使我们能够了解泥石流的行为，并确定引发运动加速的孔隙水压力（PWP）阈值。因此，GPS似乎适用于对具有微小且缓慢位移（约5毫米/天）的地球物理对象或人造结构进行连续监测。这种技术不需要“移动”站点和参考站之间有直接视线。测量可以在任何天气条件下以及夜间进行。GPS处理可以近实时进行且不会损失精度。然而，GPS的使用受到地球物理对象（山脉、植被）环境特征的限制，这些环境特征可能会构成遮挡天空视线的障碍物，并产生多路径效应。（C）2002爱思唯尔科学出版社。版权所有。
Recent researches have demonstrated the applicability of using Global Positioning System (GPS) techniques to precisely determine the 3-D coordinates of moving points in the field of natural hazards. Indeed, the detailed analysis of the motion of a landslide, in particular for a near real-time warning system, requires the combination of accurate positioning in three dimensions (infracentimetric) and Fine temporal resolution (hourly or less). The monitoring of landslides with the GPS is usually performed using repeated campaigns, as a complement to conventional geodetic methods. Continuous monitoring of landslides with GPS is usually not performed operationally, mostly because of the cost of such a system compared to conventional deformation monitoring techniques. In addition, if GPS measurements can reach a millimetre-level accuracy for long observation sessions (typically 24 h), their accuracy decreases with the duration of the observation sessions, because of errors introduced by variations of the satellite constellation and multipath effects at the sites. This study aims at determining the experimental accuracy of GPS measurements for the continuous monitoring of landslides with GPS. In particular, we want to calibrate the variation of the measurement accuracy as a function of the duration of the observation sessions. The study was carried out on the Super-Sauze earthflow (Southern Alps, France) which evolves in a channelized flow with surface displacements reaching a few tens of centimetres to a few metres per year. The GPS data were acquired during two campaigns in May and October 1999 (two reference stations were installed outside the flow and four "moving" stations distributed on the flow). The maximal 3-D cumulative displacement reaches 2.1 m during 3 weeks in May 1999. The accuracy for a 1-h session reaches 2.7, 2.2 and 5.0 mm for the north-south, east-west and vertical components, respectively. The detectability threshold for a significant motion and a given temporal resolution stands between 3.5 mm/24 h and 8.5 mm/h in planimetry, between 6 mm/24 h and 19.5 mm/h in altimetry. Thus, the motion of the flow is clearly detected by the GPS measurements and the results have been compared with those obtained with conventional geodetic methods (theodolite and electronic distance-meters) or with a wire extensometer device. In addition, combination of periodical topometric measurements, continuous extensometric and GPS measurements allows us to identify seasonal and episodic transient variations in the surficial velocity of the flow. The analysis of the relationships between rainfall (and snowfall), groundwater level, and displacements permits us to understand the behaviour of the flow and to determine pore water pressures (PWP) thresholds initiating an acceleration of the movement. GPS therefore appears applicable to the continuous monitoring of geophysical objects or of man-made structures with small and slow displacements (similar to5 mm/day). This technique does not require direct line of sight between the "moving" sites and the reference stations. Measurements can be carried out in all weather and at night. GPS processing can be performed in near real time without loss of accuracy. The use of GPS is, however, limited by the environmental characteristics of the geophysical object (mountains, vegetation), which can constitute masks limiting the visibility of the sky and create multipaths effects. (C) 2002 Elsevier Science B.V. All rights reserved.