Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
Volume 11
Issue 2
Geodesy and Cartography
Available Online: http://www.ejpau.media.pl/volume11/issue2/art-29.html


Anna Szostak-Chrzanowski, Adam Chrzanowski
Canadian Centre for Geodetic Engineering, University of New Brunswick, Canada



Increasing concerns regarding public safety, environmental protection, and efficient and safe operation of industrial enterprises dramatically increase the importance and demand for deformation monitoring in the civil engineering, mining, and energy sectors. Development of new methods and techniques for integrated monitoring, integrated analysis, and prediction (deterministic modeling) of structural and ground deformations is a subject of interdisciplinary research effort at the Canadian Centre for Geodetic Engineering (CCGE) at the University of New Brunswick. The recent developments include the Deformation Detection System (DDS) software suite for fully automated and continuous monitoring of deformations with multi-sensor systems, use of deterministic modeling of deformations in the design of monitoring schemes, and use of monitoring results in the physical interpretation of the deformation.

Key words: deformation monitoring, deterministic modeling, integrated analysis, Deformation Detection System.


Recent catastrophic disasters such as the collapse of highway overpasses in Canada; failures of levees and bridges in New Orleans and Minnesota; collapses of roofs of large civil structures in Germany, Poland, and Russia; land slides in California, Pakistan, and the Philippines; and rock failures and losses of lives in deep coal mines in China and USA have dramatically increased the demand for the development of advanced monitoring systems and their broader applications. Automation, multi-sensor integration, continuous data collection, integrated analysis and physical interpretation, and enhanced accuracy and reliability are key issues in the development of such systems.

If the monitoring system is to be used as a failure warning system, it must be fully automated to handle continuous or very frequent data collection (depending on the expected rate of deformations). It must be able to perform data processing, and visualization in near-real time, and must have sufficient accuracy and capability to trigger the alarm. In order to minimize triggering false alarms, the system must be capable of distinguishing between the actual deformation signal and noise caused by errors of observations. False alarms are expensive and lead to a wrong evaluation of the physical state of the object which may have large economic and sociological impacts. Concerning the required accuracy, most deformable objects (e.g. bridges, dams, nuclear power stations, open pit mines) require sub-centimetre or even millimetre level accuracy.

The Canadian Centre for Geodetic Engineering (CCGE) at the University of New Brunswick is dedicated to the development of new monitoring systems and new methods for integrated analysis, modeling, and prediction of structural and ground deformations using an interdisciplinary approach. Some of the significant recent developments at CCGE include: the development of the DDS (Deformation Detection Systems) software suite for fully automated and continuous monitoring of deformations with multi-sensor systems; enhancement and full automation of GPS monitoring techniques; augmentation of monitoring schemes with terrestrial emitters of GPS-like signals (i.e., "pseudolites"); the use of monitoring results in the verification of deterministic models of deformation; and a new approach to the design of multi-sensor monitoring surveys based on deterministic modeling of deformations using the finite element method. This paper gives a review of these recent developments.


The sensors used in monitoring measurements are generally grouped into geodetic techniques (terrestrial and space) and geotechnical/structural instruments (e.g., tiltmeters, extensometers, strainmeters). Among the available geodetic and geotechnical/structural technologies, there are very few, if any, sensors that can fully satisfy the above monitoring criteria as a stand alone system. Therefore, in most cases, various techniques must be combined into an integrated monitoring system.

Among geodetic techniques, the best for fully automated and continuous monitoring are GPS and robotic total stations (RTS) with automatic target recognition (e.g Leica TCA 1800). If needed, GPS can be augmented with other satellite positioning systems and/or with the terrestrial transmitters of GPS-like signals (e.g. "pseudolites"). Other, comparatively new, geodetic techniques include laser scanners and interferometric synthetic aperture radar (InSAR). They have, however, many limitations and restrictions, which still require further research and enhancements. For example, the satellite born InSAR, provides repeated radar images only every 24-35 days depending on the satellite system. InSAR also suffers from other limitations [7]. The recently developed ground based InSAR technology [19] promises significant improvement in continuous monitoring of steep slopes and embankments.

All of the discussed geodetic technologies are vulnerable to the effects of changes of atmospheric conditions (changes in the density of air due to the changes in temperature, humidity, and barometric pressure) causing:

Geodetic methods supply information on the absolute and relative displacements from which displacement and strain fields for the monitored object may be derived. Thus, geodetic surveys supply global information on the behavior of the investigated object. In some cases, however, the use of geodetic techniques may be uneconomical and may have inadequate accuracy.

There is a multitude of geotechnical instruments equipped with electro-mechanical transducers [15] that may be easily adapted for continuous monitoring and telemetric data acquisition. Usually, the geotechnical instruments are embedded in the investigated object for the duration of the monitoring project. These instruments supply only very localized information on a selected component of the deformation (e.g., only local tilt or local extension when using a tiltmeter or an extensometer, respectively).

Among the recent new developments in geotechnical instrumentation one should pay attention to the sensors of acceleration, tilt, bending, and vibrations based on the Micro Electro-Mechanical Systems (MEMS). Measurand Inc. (2006), a producer of monitoring systems based on MEMS technology, demonstrates a multitude of practical applications, particularly in slope stability measurements.

Geotechnical instruments require thorough calibration for the effects of environmental temperature, drift of the readout, and conversion constant. Once embedded within the structure, however, the geotechnical/structural instruments cannot be rechecked or recalibrated. Because of this, it is not uncommon that geotechnical instruments provide unreliable data or even fail during the life of the structure. Since geodetic measurements allow for redundancy and the possibility of statistical evaluation of the quality of the data, they generally provide more reliable results. Geodetic and geotechnical measurements compliment each other and, ideally, should be used together creating an integrated monitoring scheme. When the investigated object is located within the influence of seismic activity, the local monitoring system must be integrated with a regional system. A good example illustrating these concepts is given in [14].


The full automation of monitoring data collection and data processing was introduced by CCGE in 2000 by developing DIMONS software [16], which used only single robotic total stations (RTS) and meteorological sensors. DIMONS was followed by ALERT software [23], which permitted networking of multiple RTSs. The recently developed Deformation Detection System (DDS), which is being expanded to accommodate any types of sensors in integrated multi-sensor schemes, replaces ALERT.

Very recently, GPS has been added to DDS to work either as a stand alone fully automated GPS monitoring system or to work together with RTSs as a hybrid RTS/GPS system. In the latter case, GPS is used to control and give positional corrections to the RTSs, which may be setup within the deformation zone. GPS allows the network of RTSs to be connected to stable reference points since it does not require intervisibility between stations. Fig. 1 shows typical observation shelters of the DDS system. Fig. 1a shows one of eight RTS stations installed at the Diamond Valley Lake Project in Southern California [14] to continuously monitor three large earth dams. Fig. 1b shows a RTS/GPS shelter in a large open pit mine in Western Canada.

Fig. 1. a – RTS shelter with solar power panels, b – Typical RTS/GPS shelter

The DDS software suite is composed of a series of modules that automate surveying tasks, handle database management, and provide graphical user interfaces. The system takes advantage of the core functionality of the Microsoft systems (e.g., NT 4.0, Windows 2000, and Windows XP). There is full support for remote operation via LAN and internet connections and provider-independent database access. In addition, the software's observation and processing tasks are automated according to any desired schedule and the system is able to recover from power outages with no user intervention.

An alarm system is incorporated into the DDS software. An alarm definition is created by attaching to it one or more user defined criteria with a list of action items. The criteria can be defined for displacements, velocity, or acceleration.

DDS is completely autonomous with several self-recovery features that are critical for automated monitoring projects. The computers that run DDS are configured to automatically reboot if power is lost, allowing a backup service to complete any interrupted data collection tasks

A very unique feature of the DDS software is its automated handling of multiple-RTS networking. Due to the configuration defects in this type of RTS network, the processing of the network observations requires a special least squares algorithm that adjusts observation differences with respect to a user defined reference epoch. The results of the network adjustment are further processed using iterative weighted similarity transformation of displacements to identify unstable reference points [6] and to remove their effects.


Implementing GPS for deformation monitoring poses challenges. Displacements encountered in deformation monitoring are frequently at the sub-centimetre level. Since the practical resolution of an undifferenced GPS carrier-phase measurement is approximately 2 mm (1% of the L1 carrier wavelength of 0.190 m), monitoring millimeter level displacements in near real-time pushes the limits of the system. Achieving reliable, millimetre level precision in ‘real-time’ using GPS is not easy in favorable monitoring conditions, let alone in the harsh environments frequently encountered in deformation monitoring projects. Recent efforts at CCGE to develop GPS software for deformation monitoring in harsh environment conditions have resulted in the emergence of the Precise Position Monitoring System (PPMS) [1]. PPMS utilizes a delayed-state Kalman filter to process GPS triple-differenced carrier phases. Test results have indicated that the software is capable of detecting millimetre level displacements without having to solve for ambiguity terms. The ability to provide high precision solutions that are independent of ambiguities makes PPMS desirable for deformation monitoring since it is less susceptible to false alarms caused by cycle slips than traditional double-differenced processing methods. The trade-off in using the triple-differenced approach is a longer convergence time than for double-differenced methods. This is generally not a concern, however, for deformation monitoring applications where long term structural behaviour is of interest.

The PPMS software has recently been expanded to include fully automated data collection and processing of pseudolite signals [2]. Being a ground-based transmitter, PL error sources must be handled differently than GPS signal error sources. PPMS was modified to address nuances in PL data processing, which include cycle slip detection, PL location determination, and PL observation modelling.


Design of the monitoring scheme requires decisions to be made regarding the type, location, density, and accuracy of monitoring sensors. The location of the sensors or the observed targets must include points where maximum or critical deformations are expected [8].

The design of a monitoring scheme should be based on a good understanding of the physical process which leads to deformation. The investigated deformable object should be treated as a mechanical system, which undergoes deformation according to the laws of continuum mechanics [22]. This requires the causative factors (loads) of the process and the characteristics of the object under investigation to be included in the analysis leading to the design. This is achieved by using deterministic modeling of the load-deformation relationship using e.g., the finite element method (FEM). Thus the design process requires an interdisciplinary cooperation between specialists in various fields of geoscience and engineering, including structural, rock mechanics, and geodetic engineering, depending on the type of the investigated object.

To illustrate the use of deterministic modeling in designing an integrated monitoring scheme, an example of a 75 m high, Concrete Face Rockfill Dam (CFRD) resting on a 60 m thick till is given. Fig. 2 shows expected horizontal and vertical displacements caused by filling the reservoir [21].

Fig. 2. Predicted displacements [m] after filling the reservoir a – horizontal b – vertical

As one can see from the modelled displacements, the largest displacements are expected to occur at the upstream face of the dam, which is covered by a concrete slab. It is the most crucial area for monitoring the deformation. Since the upstream face is under water, the monitoring scheme should be designed to have geotechnical instruments such as MEMS sensors of 3-D deflections (tilts) and a fibre-optics strainmeter embedded in the concrete slab.

The rest of the dam could be monitored by geodetic methods using, for example, robotic total stations and GPS. Final details of the design including the required density of the instrumentation, accuracy requirements, and frequency of observations would require full evaluation of the deterministic model. For example, by modeling the expected deformation at various water level stages in the reservoir, one could determine the rates (velocities) of deformations. This information would add in determining the required frequency of repeated surveys. Bond et al. [3] give an example of designing a monitoring scheme for monitoring an open pit mine based on the finite element modeling of the rock slope deformation.


Analysis of deformations of any type of deformable body includes geometrical analysis and physical interpretation. Geometrical analysis describes the change in shape and dimensions of the monitored object, as well as its rigid body movements (translations and rotations). The ultimate goal of a geometrical analysis is to determine the displacement and strain fields in the space and time domains for the whole deformable object. The Generalized Method of Geometrical Deformation Analysis [4,9] allows for a simultaneous analysis of any type of observations (geodetic and geotechnical) even if scattered in space and time. The displacement field is obtained by iterative least squares fitting of an appropriate displacement function to the measured deformation quantities. Examples are given in [8].

Physical interpretation is based on establishing the relationship between causative factors (loads) and deformations. This can be determined either by:

By comparing the geometrical model of deformations with the deformations obtained from the deterministic model, one can determine the actual deformation mechanism [10] or verify the designed geomechanical parameters [12]. Integrated analysis may also explain the causes of deformation in the case of abnormal behaviour of the investigated object. Thus, the role of monitoring surveys is much broader than serving only as a warning system. As described earlier, the ultimate goal of deterministic modeling of deformations is to develop a prediction model, which can help in designing a monitoring scheme.

The most critical problem in modeling and predicting deformations, particularly in rock or soil material, is to obtain in-situ characteristics of the materials. The difficulty in determining material characteristics is the main cause of uncertainty in deterministic modeling of deformations. Results of properly designed monitoring schemes may be used to enhance the deterministic model (e.g. by correcting the material parameters of the observed object). This can be achieved using forward or back analysis [10]. In turn, the enhanced deterministic model may be used in improving the monitoring scheme.

Recent research at CCGE has demonstrated how to successfully incorporate the combined results of deterministic modelling and monitoring observations in the analysis and physical interpretation of engineered and natural structures. In particular, research was implemented in ground subsidence studies caused by mining activity [11] and in modeling deformations of large earth and rock filled dams [20]. In these projects, a “large-scale” approach has been used. The approach is based on replacement of a complex structure or a rock mass by one or a number of blocks characterized by equivalent (averaged) material properties. The criteria governing the division in to blocks of the rock mass are refered as S-C method [20].


Significant progress has been made at the CCGE in the development of fully automated monitoring systems and in the deterministic design and analysis of deformation surveys. The effects of changeable atmospheric conditions on geodetic measurements and the effects of improper calibration and poor reliability of in-situ geotechnical/structural instrumentation still remain as the main problems of current monitoring systems. Further research must be devoted to the development of integrated monitoring systems in which the two types of measurements complement each other to increase the reliability. Geodetic engineers should become acquainted with principles of continuum mechanics. They should utilize deterministic modeling of deformations in order to make sound decisions regarding the design and analysis of monitoring surveys.


The research reviewed in this paper has been supported by the Natural Sciences Research Council of Canada, Atlantic Canada Opportunities Agency, and the Public Safety and Emergency Preparedness Canada Research Fellowship in honor of Stuart Nesbitt White.


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Accepted for print: 12.06.2008

Anna Szostak-Chrzanowski
Canadian Centre for Geodetic Engineering,
University of New Brunswick, Canada
P.O. Box 4400, Fredericton, N.B., E3B 5A3, Canada
email: amc@unb.ca

Adam Chrzanowski
Canadian Centre for Geodetic Engineering,
University of New Brunswick, Canada
P.O. Box 4400, Fredericton, N.B., E3B 5A3, Canada

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