Development and testing of an integrative 3D early warning ... · GEOTECHNOLOGIEN Science Report alpEWAS Development and testing of an integrative 3D early warning system for alpine

GEOTECHNOLOGIEN Science Report alpEWAS Development and testing of an integrative 3D early warning system for alpine instable slopes

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Development and testing of an integrative 3D early warning system for alpine instable slopes (alpEWAS)

K. THURO1, TH. WUNDERLICH2 & O. HEUNECKE3

1 Prof. Dr. Kurosch Thuro, Lehrstuhl für Ingenieurgeologie, Technische Universität München, Arcisstraße 21,

80333 München, [email protected]; http://www.geo.tum.de. 2 Prof. Dr. Thomas Wunderlich, Lehrstuhl für Geodäsie, Technische Universität München, Arcisstraße 21,

80333 München, [email protected]; http://www.geo.bv.tum.de. 3 Prof. Dr. Otto Heunecke, Institut für Geodäsie, Universität der Bundeswehr München, 85577 Neubiberg,

[email protected]; http://www.unibw.de/ifg.

1 Introduction Although great advances in the recognition, pre-diction and mitigation of landslides have been made in the last few years, major events espe-cially in alpine regions still claim a high social and economical tribute. Especially through extreme weather conditions, as e.g. the intense rainfall in August 2005, instable slopes can be activated and endanger people, settlements and goods in its surrounding. Currently an increase of this problem caused by the global climate change can be observed. Recent landslides, which occurred in the alpine region, demonstrate the need for a deeper un-derstanding of the geological and physical proc-esses, which can lead to a spontaneous failure of a natural slope. Major rockslides as Vajont (1963, Italy) or Randa (1991, Switzerland) and recent minor events as Sibratsgfäll (1999, Austria) prove the destructive potential of these mass move-ments and the need to investigate the mechanics of such processes more deeply. Progress in the assessment of the land slide risk will only be achieved if the triggering processes and the kinematics of the movements are better under-stood. To accomplish this task an assumedly instable slope has to be examined for its engineering geo-logical properties and then has to be observed continuously with a suitable monitoring system. Exclusive instruments and methods to achieve this are available, but for economical reasons

they are rarely used. At the same time the num-ber of localities with need for monitoring is rising noticeably. Therefore the goal of the alpEWAS joint project, which is being carried out by the Technische Universität München and the Universität der Bundeswehr München, is to develop and test a relatively economic and widely applicable moni-toring and early warning system at a designated location. The monitoring system is based on the integra-tion of innovative and economical measuring technologies to a Geo-Sensor Network. The sur-face movements will be detected punctiform and highly precise with the Global Navigation Satellite System (GNSS) as well as extensively in a large part of the landslide area through reflectorless tacheometry; the measurement of the move-ments in the depth alongside boreholes will be done by using a newly adapted Time-Domain-Reflectometry (TDR) System. Parallel to theses measurements the registration of the hydrostatic pore pressure, as well as the climatic conditions at the site will be carried out. In this way the 3D movements of the slope, which are determined nearly in real time, can be compared with the surrounding conditions (precipitation, hydrostatic pore pressure etc.) and can be analysed for trig-ger mechanisms. Through the large amount of data collected by the system (in time and space) it should be pos-sible to determine causal and temporal coher-ences between the most important influencing factors and the movement of the instable slope within a relatively short period of time (6 to 9 months), allowing the definition of critical thresh-


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old values. By using an automated alarm func-tion, which informs the responsible authorities when the threshold is exceeded, an early warn-ing system can be implemented. A major task of the alpEWAS project is to develop the necessary hard- and software and to test the system at a designated site. A real cost advantage of the readily developed monitoring system is achieved by making remote maintenance and inquiry possible. All important functions can be queried and controlled from the project office via Modem, reducing the costs for personnel in comparison to conventional meas-urements by eliminating the need for repeated manual measurements. Furthermore the installa-tion costs are – when compared to the amount of data which is gathered in space and time –

relatively low due to the used measuring tech-nologies (reflectorless tacheometry, low-cost GPS and TDR). The linking of the different measuring units with the local control center will as far as possible be accomplished by using WLAN, which makes the usage of an expensive mobile telephone system or beam radio unnec-essary.

2 Project Site The landslide “Aggenalm”, situated in the Sudelfeld area near Bayrischzell (Bavaria), has been selected as the location for the installation of the early warning system (Figure 1). After a first engineering geological investigation, the lo-cation has been proven suitable due to its movement rates of about 2 cm per year and the anticipated maximum depth of the landslide of about 25 m in most areas. Additionally the Ag-genalm, a grass slope interspersed by single rock blocks, is ideal for the development and training of the new monitoring strategies needed when using reflectorless robot.

Figure 1. Orthophoto (scale ca. 1:5000) of the landslide Aggenalm with displacement vectors in the scale ca. 1:1 (observation period: 2003-2004). The shown results emanate from periodic geodetic measure-ments of the slope which were carried out on behalf of the Bavarian state office for the environment (Bayerisches Landesamt für Umwelt). In the upper half of the picture a secondary landslide which oc-curred in 1997 can be seen. The Aggenalm and the access road to the ski resort Sudelfeld are affected by the movement.


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3 Deformation measurement tech-niques

3.1 Time Domain Reflectometry (TDR) Time Domain Reflectometry (TDR) is widely known as a system for the measurement of soil moisture (e.g. TOPP, DAVIS & ANNAN 1980). With few modifications TDR can also be used for the monitoring of localized deformation in rock and soil. To date this application has only found wider acceptance in North America, while it is still largely unknown in Europe. This is surely based on the fact that so far most of the research has been carried out at the Northwestern University (Evanston/Chicago, Illinois) under the leadership of Dowding and O’Connor, who have without doubt proved the usability of TDR in landslide monitoring (O’CONNOR & DOWDING 1999). Especially the comparably low installation costs and the possibility to perform continuous meas-urements make TDR an interesting alternative to inclinometers. Presently, TDR landslide monitor-ing systems are capable of determining the exact depth of the observed deformation zone, while only a semi quantitative statement can be made of the amount of movement. The orientation of the movement can not be determined at all. Fur-thermore in most instances the application is limited to the measurement of localized deforma-tion as it is typically observed in rock (e.g. local-ized shearing alongside joints) (KANE, BECK & HUGHES 2001). In the opinion of the authors some of these dis-advantages can be overcome by defining stan-dardized installation procedures (e.g. grout type, coaxial cable type) adjusted for different geologic settings. Furthermore new methods for the analysis of the received TDR data are under de-velopment, especially when multiple TDR meas-uring points are connected to produce a 3D model of the deformation zone. The monitoring of deformation in rock/soil using TDR is based on an indirect measuring method: the deformation itself is not measured (as with an inclinometer) but a directly dependant value, the

change in impedance of a coaxial cable as a re-sult of deformation, is measured. TDR can be described as “cable-based radar” and consists of two basic components: a com-bined transmitter/receiver (TDR cable tester) and a coaxial cable (Figure 2). The TDR cable tester produces electric impulses, which are sent down the coaxial cable. When these pulses approach a deformed portion of the coaxial cable an electric pulse is reflected and sent back to the TDR Ca-ble Tester. The reflected signals are collected and analysed. As with radar, by measuring the time span between emission and reception of the signal the distance between the TDR Cable Tester and the deformation can be determined. Furthermore by analysing the reflected pulse (amplitude, width, form etc.) information about the type and amount of deformation can be ob-tained. For landslide monitoring a semi rigid coaxial ca-ble is installed into a borehole and connected to the rock mass with grout. There are basically three different installation methods (Figure 3): 1. The TDR cable is installed parallel to an incli-nometer within the same borehole; 2. the coaxial cable is installed into a sheared inclinometer cas-ing, therefore extending the lifespan of an incli-nometer borehole; 3. the coaxial cable is installed into a borehole of its own. The installation parallel to an inclinometer in the same borehole is primarily for research pur-poses, since a direct comparison of inclinometer measurements (direct measuring method) with the TDR readings (indirect measuring method) is made possible. For this reason this method will be an important part of the ongoing research. Nevertheless options 2 and 3 are probably the most appropriate installation methods for com-mercial use: option 2 because it extends the lifespan of an existing inclinometer borehole, and option 3 because a sole TDR installation can be established at comparably low costs, because of the relative small boring diameters required and the low cost of the coaxial cable. Furthermore with option 3 the grout and other installation pa-rameters can be optimized to greatly enhance the performance of the TDR measurements.


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Figure 2. Basic setup of a TDR measuring site. The coaxial cable is installed into an instable slope and connected to the TDR cable tester. As soon as the coaxial cable is deformed by the mass movement a peak can be seen in the reflected sig-nal. Its amplitude is dependant to the amount of deformation taking place.

Figure 3. Possible installation setups for a TDR coaxial cable into a borehole with and without an inclinometer.


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Many different factors influence the measure-ment of deformation with TDR (O’CONNOR & DOWDING 1999). Generally two groups of effects can be distinguished: the influence of the defor-mation itself and the installation parameters of the TDR system. TDR measurements are influenced greatly by changes in the geometry of the measurement cable. The type (shearing, extension and com-pression) and the amount of deformation, as well as the width of the deformation zone, affect the received signals. Prliminary simple tests have shown that discerning the different types of de-formation is not always possible. However, espe-cially with progressive deformation, a determina-tion of the deformation type is sometimes possi-ble. It is evident that the components used in a TDR system, and the way it is installed into a land-slide, influence the measurement. In particular, two parameters stand out in their importance: the type of coaxial cable used and the physical prop-erties of the grout. The material from which the cable is made, its diameter and the length all influence the measurements. Generally, when using thicker cables, larger total deformations can be observed before the cable is severed. At the same time, the sensitivity of the system to small movements is reduced. Accordingly, thin-ner cables should be used for landslides with low deformation rates, and thicker cables for “faster” landslides. The grout is the interface between the cable and the rock mass. It is, therefore, important to match the physical properties of the grout to the particu-lar geology, especially when working in soil. If, for example, the grout is too strong, a pillar-effect might occur whereby soil moves around a pillar over-stiff grout, resulting in too little or no defor-mation of the TDR cable. Varying the type of cable and the grout mix to suit the surrounding geology and the anticipated deformation rates will enhance the quality of the received TDR measurements. This is one main task of the ongoing research: defining certain installation procedures for different geological settings and deformation rates. Furthermore a careful calibration of these setups is a pre-requisite for ensuring the maximum quantity and quality of information (especially the deformation type and amount) through the indirect measure-ment of deformation with a TDR system. Within the alpEWAS project these newly defined installation setups, which were determined in

laboratory shear tests, will be tested for the first time in the field. Signal analysis software will be developed, which will allow an automated proc-essing of the TDR signals. The TDR measure-ments are then compared and if necessary fur-ther calibrated with parallel inclinometer meas-urements. 3.2 Reflectorless Robot-Tacheometry The component RL-TPS (Prismless Terrestrial Positioning System) fulfills the task of interpola-tion within the joint project. Its aim is to densify the displacement pattern determined by TDR and GNSS at only few selected loci and focusses on discovering local maxima or singularities. To at-tain high economic efficiency it should be avoided to fit targets with special prisms. An ex-ception is only allowed for those points which are needed for continuous testing the stability of the observation station itself and to confirm the mo-tions of the GNSS and TDR spots. Most objects to observe will be natural targets, e.g. rocks standing out of the slope and tree stumps. Spatial polar methods based on automatic target-ing robot-tacheometres with prismless EDM are well suited for periodical surveying of these ob-jects. By corresponding programming the geo-detic precision instruments are able to scan suit-able objects with a dense grid. The 3d-model derived from this grid can be investigated for dis-placement and deformation by comparison with a 3d-template from the initial epoch. The 3d-templates themselves shall be determined in close-range manner by a terrestrial laser scanner with high resolution. To determine the spatial components of the movement, corresponding software has to be developed based on known geodetic algorithms. In addition corresponding statistical tests of significance have to be pro-vided. The solution could be substantially improved, if it were possible to make use of the internal image information collected by the automatic target rec-ognition unit. In this way contours could be ex-tracted and possibly grey values could be com-pared. The Chair of Geodesy disposes of an in-strument with such an interface and pioneered successfully automatic pointing at natural targets. In spite of this the fix focus feature of the internal camera prevents the application for the present problem, because less than 500 m distance im-ages will be poorly defined. A single manufac-turer has developed a prototype of a focusable internal camera; although it is not yet on the mar-


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ket, an operative instrument based on the actual tacheometry technology was ordered by the Chair of Geodesy. First tests and calibration pro-cedures already are planned and must be scheduled before the system can get operative at the site. These additional tasks must be performed to reach the highly innovative final aim: to realize the vision of a system, able to autonomously find and select suitable natural targets. Only with the image information it will become possible to train a survey robot to search systematically suitable natural targets on a slope, to scan them and to subsequently perform a periodical motion check. The necessary strategies have to be developed and programmed in a way that enables the RL-TPS to adapt itself for changing atmospheric and topographical conditions. The accuracy, the promptness and the reliability of the RL-TPS will be slightly lower than TDR and GNSS as the sophisticated processes of observation and evaluation will lead to a certain delay with respect to the numerous natural targets. Another reason comes from a necessary generalization which cannot be prevented during the modelling rou-tines. Nevertheless, in total the evidence con-cerning the entire behaviour of the landslide will be of substantially increased value in order to gain insight into the complex kinematics. The high economic advantage of the strategy to use natural objects as targets is opposed by an unavoidable disadvantage: especially in the alps those targets will be covered with snow during winter season and therefore will be invisible. Moreover, it has to be expected that due to the cold weather the supply of solar energy will be weak. Therefore we suggest to let the TPS scan the current snow cover once a week. This infor-mation can be used to compute the water volume from melting snow in spring to incorporate the most efficient landslide trigger into the general model. Low-cost GNSS and TDR are very suitable solu-tions to continuously gather highly precise infor-mation about the movements on the surface and underground, respectively. By doing so, the ten-dencies at a few selected points within an insta-ble slope can be detected economically. Despite using great carefulness to select representative sites for the measurements, they still are only spot checks, which can miss areas with high rates of movement and therefore make a deeper understanding of the underlying landslide mechanism difficult.

Thus it is necessary to economically gain infor-mation covering the complete landslide area, in order to incorporate all problematic regions into the monitoring system by either moving existing sensors or installing new ones. When high rates of movement are encountered, the methods of aerophotogrammetry and satellite remote sens-ing are used. At lower rates of movement and the need for continuously updated information, TPS is to prefer for economical an accuracy reasons. However, a dense placement of reflectors within an instable slope is not reasonable. The snow depths which have to be expected in the moun-tains force the installation on long metal posts. These would not only deface the slope and pro-duce an unwanted psychological sensation of threat, but with time would also become askew and attract lightning during thunderstorms. Addi-tionally the installation of the posts would lead to extra costs, especially when using active reflec-tors (dependent on manufacturer), which need an extra energy supply. Thus an economic solution must aim at natural targets. This has already been tried using reflectorless tacheometres, which sweep the terrain in a manner comparable to a scanner, but did not lead to a verifiable suc-cess when used for the monitoring of instable slopes – other as when used for the observation of snow accumulations for the mitigation of ava-lanches (SCHEIKL et al. 2001). The new approach proposed in this project is now trying to combine the advantages of two established methods and at the same time in-clude an awaited instrumental innovation. The idea is to first detect a great number of natural targets as e.g. large rocks or tree trunks using terrestrial laser scanning (TLS) and then to local-ize these with a terrestrial positioning system (TPS). First the target objects will be aimed at in their last known position and scanned using a reflectorless measuring precision tacheometre (STEMPFHUBER & WUNDERLICH 2004). The result-ing 3D-model of each structure is then compared to the original template from the TLS (WUNDERLICH et al. 2005) and statistically checked for changes in its position in space. Later the internal camera of the tacheometre, which is usually used for the automatic aim on reflectors, will support the reflectorless aim by conduction a contour comparison. First achieve-ments have been made with this method at the Chair for Geodesy (TUM) using the example of the automatic recognition of church spires as geodetic orientation (WASMEIER, 2003, 2004). Momentarily the technique is limited by the inter-


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nal camera, which, due to its fixed focus, can only picture objects in distances above 500 m sharply. However, one manufacturer has just developed a tachymeter containing a camera with adjustable focus (WALSER & BRAUNECKER 2003), so that it can be expected to be brought onto the market soon. Then the third phase is entered in which a great advance in the operating efficiency can be achieved. For such an instru-ment a control system can be developed, which will allow it to automatically search a slope for fitting natural objects, measure them and repeat-edly check them for a change in position. There-fore it can be installed at virtually any location and find targets by itself, to then start with their periodical survey. In a symbiosis with the other two systems, TDR and GNSS, a nearly perfect intelligence unit is produced, which enables to establish an early warning system and to better understand the mechanical processes within a landslide. 3.3 Global Navigation Satellite System The primarily contribution of the Universität der Bundeswehr München to the alpEWAS project will be an all weather proof Low-Cost-GNSS-System which continuously records movements on the surface of the instable slope with the qual-ity of a few millimetres. It concerns the develop-ment of a prototype of a GNSS-Monitoring Com-ponent which in particular features the following special characteristics: ⋅ Low-Cost-GNSS-Sensor technology (resp.

Low-Cost-GPS-Sensor technology);

⋅ WLAN-Communication between the stations (wireless data transmission);

⋅ autonomous power supply of the Rovers;

⋅ flexibility of the analysis through (at any time adaptable) options of post processing;

⋅ possibility for remote maintenance and re-mote inquiry of the system (remote desktop operation);

⋅ separation between data recording and es-sential evaluation (especially time series analysis); defined ASCII-interface (“dual sys-tem”);

⋅ possibility of incorporation of existing (proofed, powerful) program systems;

⋅ open system to integrate other sensors resp. to be adapted to other sensors (“multisen-sorsystem”, component of a Geo-Sensor Network).

After the installation the (entire) system – the GNSS-Monitoring Component is only a part of the planned Geo-Sensor Network – will continu-ously provide measuring data. Its presentation and analysis are essential parts of the later pro-ject phases (see below). Beside the development and trial of the three technological monitoring systems TDR, GNSS and TPS, their integration into the Geo-Sensor Network is the centre of the scientific project. This includes at first a purely technical and later a software-related, data base oriented combination of the measuring results. This represents another focal point of the work done by the Universität der Bundeswehr München. Up to date the GNSS-Monitoring Component de facto is a purely GPS-Component. If (as soon as) available, it should be changed to receivers, which are able to register GALILEO and option-ally GLONASS signals as well. This is presently not possible, but is, however, imminent. The planned set-up of the online Low-Cost-GPS-Systems (L1-receiver, no RTK availability) pro-vides four stations/receivers. Two respectively three stations of them are installed in range of the slide slope and the fourth receiver on a cen-tral station in the presumably stable range in the near vicinity.


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Figure 4. Measuring configuration of the GNSS-Monitoring Component at the test site Aggenalm. The sketched configuration is currently tested in the scope of a still ongoing dissertation at the Universität der Bundeswehr München. Beside the OEM Boards Novatel Smart Antenna (re-ceiver/antenna combination) different sensors are also integrated in this test configuration like temperature sensors, voltmeters for control of the battery voltage in the solar mode, geotechnical sensors such as extensometer and hydrostatic measuring devices. At present a year-round field trial is coming up, the previous test structure is operating since a few months on the campus of the University of the Bundeswehr Munich. The system can be remotely maintained and con-trolled in the viewer modus (at any time) by thirds as well. At the computer centre (host system), where two computers are provided for the system control, the access to 220 V power supply and to the in-ternet (telephone) is necessary. The other sta-tions of the GNSS-Monitoring Component (rover stations) maintain a self-sufficient, autonomous

power supply. The conception for the Aggenalm landslide provides solely solar panels and aban-dons an additional/alternative use of wind en-gines. This is guaranteed by the sufficient dimen-sioning of the panels and the buffer batteries. Demands to the GNSS-Rover Stations are: ⋅ preferably little signal shading of the orbit

resp. space segment (no signal obstacles);

⋅ quasi-optical view to the computer centre (with WLAN Access Point); obtainable through a raised set-up of the WLAN anten-nas (transmitting poles), the choice of the antennas and/or a repeater station (planned in the financial means including necessary the self-sufficient power supply, see below);

⋅ proximity to TDR-Measuring Arrays, to be able to analyse the obtained information ori-ented in the superior reference frame and in-tegrate this data into the Geo-Sensor Net-work, as well as, the data of the TPS.

Technically speaking, the GNSS-Monitoring Component should revert to Low-Cost-receivers


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with the possibility of a post processing. On the one hand for cost reasons (RTK-systems are 10-fold more expensive) and on the other hand for the advantages which arise when using the op-tion controlled analysis (comp. HARTINGER, 2001). Among others the update of the time in-terval is arbitrary, it usually lies in the array of approx. 15 min. up to 1 h. Beside other aspects this is also of importance to the achievable accu-racy of the base lines: the longer the time period in which phase measurements in the OEM board are acquired, the better the positioning accuracy may be expected. The studies of the GPS-Sensor Novatel Smart Antenna, conducted at the Universität der Bundeswehr München, show, that an accuracy in the scope of a few millimetres for the base lines can be achieved using 15 min. intervals.

4 Integration and Automation In addition to the development and testing of the three measuring systems, their integration into a combined Geo-Sensor-Network is a main task of the research project (figure 5). On the one hand this applies to the development of techniques and software for the database oriented combina-tion of the data, on the other hand also to the gain of scientific knowledge by means of the analysis and interpretation of the data. WLAN (54 Mbps data rate) is earmarked for the data transmission between the rover stations, at which the GNSS, TPS, TDR, piezometer and climate measurements are collected, and the computer centre. With WLAN clear ("quasi-optical") visibility up to 3 km can be bridged; adequate antennas presumed. With the distinct slope morphology at the Aggenalm landslide the direct visibility is severely limited, so that a re-peater station is planned. With regard to the de-velopment of a flexible monitoring system the incorporation of such a relay station is also of fundamental interest, however. Compared to the usual transmission path (esp. with RTK-systems) WLAN offers several advantages and starts to be

established. Basically every sensor with a RS232 interface can be integrated to the net using a COM server. Within the project the batch controlled processing will be carried out with the multivendor capability software GravNav Waypoint (see www.waypnt.com). GravNav is thereby inte-grated in a LabVIEW-Programing, National In-struments (see www.ni.com/labview), which manages the sampling and selecting of the sen-sor knots. As a result of the LabVIEW/GravNav-pre-processing the base lines (this means time information, 3D coordinates differences, as-signed covariance matrices) are applied through an open interface to the automated evaluation system GOCA (GPS Control and Alarmsystem; developed at the Fachhochschule Karlsruhe, see e.g. KÄLBER; et all, 2001a, b, see www.goca.info). GOCA presents in this concep-tion basically a highly sophisticated analysis tool for monitoring tasks, in which all features of the time series theory (filter operations as moving average and spline approximation, trend estima-tion, Kalman-filtering etc.) are realized, as well as, e.g. alarm functions (via SMS, e-mail, etc.) by the exceedance of thresholds. Furthermore, GOCA offers a nearly perfected visualization component. Also results from tacheometric ob-servations can be integrated (DANESCU, 2006). Finally however, GOCA may be replaced by any other program which enables the analysis of time series. For the combination with all the other data sources (TDR, TPS, meteo-sensors, …) – this is not possible with GOCA – the development of an adequate, data base orientated and with GIS-functionalities equipped software within this pro-ject is planned. This should be done in a similar way as the programs DIVA by the diploma thesis CRAUSE & ELING (2001) and the program ANALYSIS by the diploma thesis GLÄSER & KNAUER (1999). Furthermore a cooperation and coordination with the participants of the joint pro-ject EGIFF (“Entwicklung geeigneter Informa-tionssysteme für Frühwarnsysteme”) is arranged.


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Figure 5: Schematic illustration of an integrative 3D early warning system for instable slopes. GNSS and TDR continuously gather highly precise punctiform information about the movements on the surface and underground, respectively. The TPS in form of a reflectorless robot-tacheometre can gain dis-placement information covering most of the landslide area. Furthermore triggering mechanisms are observed using piezometers (hydrostatic pore pressure) and a meteorological station (precipitation). When combining all the different measurements, a 3D model of the slope and its movements can be derived in temporal correlation to the triggering parameters. The measured data is transmitted to the master station via WLAN and stored in a central computer. The data can be accessed and downloaded from a remote computer for further analysis and interpretation.


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The software component to be developed should offer possibilities as an information system for the user on manifold ways of (interactively) getting access to the data. Here it is stated that the data from different components TDR, GNSS and TPS (“reaction quantities”) are already pre-processed and if necessary reduced. In an ideal case the new software tool only will handle co-ordinates in a common reference frame with respect to the reaction quantities. (Minimum-)Characteristics of the new software component to be developed are: ⋅ Input of pre-processed data from TDR,

GNSS and TPS; gauge data and meteo-sensors, storage in a data base, preferably MS ACCESS;

⋅ sophisticated possibilities to choose interest-ing sensors (Visual Basic- and/or MatLab-programming, to see the allocation of the sensors at the slide, activation via „click“);

⋅ Description of single time series numerically and graphically, including a zoom-function;

⋅ Combination of any selectable sensor (e. g. comparison of impact quantities and reac-tion, comparison of adjacent sensors);

⋅ alert function after reaching limiting values (thresholds);

⋅ additional information for the sensors (digital images, specifications, maintenance, re-marks, …).

The software should be easy and intuitive to handle, especially for third persons, who are not involved to the project permanently, to get a quick overview. A modular composition is in-tended. At the end only the main user interface must be changed to make the software available for another project in a similar way. In the course of the geologic examination of the received data first simple causal and temporal coherences between the parameters, which in-fluence the slope (e.g. precipitation), and the occurring movements will be identified. This easy analysis can be done within a relatively short period of time after starting the measurements and will lead to the definition of first threshold values for the early warning system. Then, through creation of numerical models of the in-stable slope using the Itasca UDEC and FLAC (Itasca) code, the geomechanical behaviour of the slope can be analysed more precisely. The continuously collected measuring data is inte-grated into the models leading to their constant improvement. The resulting better understanding

of the trigger, mechanics and damage potential of the landslide is used to optimise the defined threshold values.

Literature CRAUSE, C. & ELING, D. (2001): Entwicklung ei-nes Datenvisualisierungs- und Analysepro-gramms für die Überwachungsmessungen der Okertalsperre im Harz. - Diplomarbeit Universität Hannover, Geodätisches Institut.

DANESCU, A. (2006): Case Studies Related to a New Approach of the GPS-Based Online Control and Alarm System Package Software for Stan-dard and non-GPS Application. - Diplomarbeit Universität der Bundeswehr München, Institut für Geodäsie.

GLÄSER, A. & KNAUER, C. (1999): Beurteilung von Deformationsprozessen mit der Hilfe der Filterung von Zeitreihen und der Ableitung von Konfidenzbändern. - Diplomarbeit Universität Hannover, Geodätisches Institut.

HARTINGER, H. (2001): Development of a Con-tinuous Deformation Monitoring System usind GPS. - Ingenieurgeodäsie – TU Graz (Hrsg. F.K. Brunner), Shaker-Verlag, Aachen 2001.

KANE, W.F., BECK, T.J. & HUGHES, J.J. (2001): Application of Time Domain Reflectometry to Landslide and Slope Monitoring.- TDR 2001 - Second International Symposium and Workshop on Time Domain Reflectometry for Innovative Geotechnical Applications, Infrastructure Tech-nology Institute, Northwestern University, Evanston, Illinois, U.S.A.

O’CONNOR, K.M. & DOWDING, CH.H. (1999): GeoMeasurements by Pulsing TDR Cables and Probes.- CRC Press, Boca Raton.

SCHEIKL, M, GRAFINGER, H. & POSCHER, G. (2001): Entwicklung und Einsatz eines automati-schen Fernüberwachungssystems basierend auf einem Laserscanner.- in: Tagungsband zur 11. Int. Geodätischen Woche Obergurgl, Wichmann-Hüthig Verlag, Heidelberg.

SINGER, J. & THURO, K. (2006): Development of a continuous 3D-monitoring system for unstable slopes using Time Domain Reflectometry. – 10th IAEG Congress, Nottingham, United Kingdom, 6-


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10 September 2006, Geological Society of Lon-don (in press).

SINGER, J., THURO, K. & SAMBETH, U. (2006): Entwicklung eines kontinuierlichen 3D Überwa-chungssystems für instabile Hänge mittels Time Domain Reflectometry (TDR).- Felsbau 24 (3), 16-23.

STEMPFHUBER, W. & WUNDERLICH, TH. (2004): Leica System 1200: Auf dem Weg zur Sensor-synchronisation von GPS und TPS für kinemati-sche Messaufgaben.- AVN, 111.Jg., Heft 5, S.175-184, Wichmann-Hüthig Verlag, Heidel-berg.

TOPP, G.C., DAVIS, J.L. & ANNAN, A.P (1980): Electromagnetic Determination of Soil Water Content: Measurement in Coaxial Transmission Lines.- Water Resources Research 16, Nr. 3, S. 574-582.

WALSER, B. & BRAUNECKER, B. (2003): Automa-tion of Surveying Systems through Integration of Image Analysis Methods.- in: Proc. of Optical 3D Measurement Techniques VI-1, Zürich.

WASMEIER, P. (2003): The Potential of Object recognition Using a Servo-Tacheoemter TCA2003.- in: Proc. of Optical 3D Measurement Techniques VI-2, Zürich.

WASMEIER, P. (2004): Potenzial der Objekter-kennung mit dem Servotachymeter TCA2003.- Geomatik Schweiz, Heft 2.

WUNDERLICH, TH., SCHÄFER, TH. & ZILCH, K. (2005): Schadenserkennung an einer Spannbe-tonbrücke durch reflektorlose Deformationsmes-sungen.- in: Festschrift 60. Geb. Prof. Bancila, S. 60-68, TU Politehnica Timisvar.

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