1 INTRODUCTION

When it comes to GIS environmental modellingapplications, in many respects GIS software can beconsidered comparable to a programming language.Unfortunately, however, the typical environmental GISusers are focused on environmental issues and onlyrarely do they have the additional technical knowledgenecessary to develop new GIS applications. As aconsequence, most domain experts are forced to workwith GIS that have predefined underlying datastructures and ‘standard’ interfaces.

This chapter will deal with the issues to beconsidered by the designers and programmers of suchturn-key applications within the areas of environmentalmonitoring and assessment. Each distinct type ofsystem presents its own demands to the designer andtogether these requirements may form a ‘requirementsmatrix’. Some characteristic examples of applicationswill be given together with a closer look at the demandsthat the individual applications make.

First it is useful to distinguish between thevarious types of environmental monitoring andassessment systems. In monitoring systems emphasisis placed on data collection, pre-processing, andquality control. Analysis systems focus on usingtools to manipulate and model data. Informationsystems, on the other hand, are more concernedwith the storage and management of data(Ji and Mitchell 1995).

2 MONITORING SYSTEMS IN GENERAL

There are many different types of monitoringsystems. Many of them automate the process ofdata collection and (pre-) processing – a task oftenhidden from the ordinary user. Monitoring itselfmay be implemented in several different waysdepending on the type of system under study. Whendesigning an environmental monitoring system, thefollowing factors should be taken into consideration:

● the acceptable time delay is likely to range fromtrue real-time monitoring to manual samplingwith a following laboratory analysis;

● the requirement to control quality may range fromshowing pure raw data to a complete qualityassurance/quality control (QA/QC) procedure;

● there is often a distinction between manual andfully automated data sampling systems.

Whatever method is used for the actual monitoring,the process involves the following steps:

1 a communication task which takes data from asensor (or other information source) andcommunicates it to a receiving monitoring system;

2 pre-processing the data using steps such ascalibration, checking, and formatting;

3 storing the data in some sort of database;4 presenting the data in an appropriate form to users.

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This chapter deals with some aspects of using GIS in environmental monitoring systems.Issues concerning real-time monitoring, data quality, the use of GIS in combination withmathematical modelling, and other possibilities for creating GIS-based monitoring systemsare examined. The discussion of environmental systems highlights examples of local andregional real-time monitoring and decision support. Hydrographic examples concerned withmonitoring the Ringkøbing Fjord, Denmark and the Øresund Sound between Denmark andSweden clearly demonstrate the value of GIS in environmental applications.

Hitherto monitoring processes, and thus monitoringsystems, have been rather mechanical. Depending onthe specific task, monitoring may have been donewith the assistance of one or more specialisedstandard systems, such as supervisory control anddata acquisition (SCADA) systems.

The reason for introducing GIS into the puremonitoring process is mostly connected to a user-interface requirement. By introducing GIS at thisstage it is possible to utilise mapping functions todisplay objects such as measurement stations.Furthermore, it can be of great value to keep thecomplete system within the framework of the GIS,especially if the required data processing tasks involvespatial analysis.

3 THE ROLE OF GIS IN ENVIRONMENTALMONITORING

GIS, not surprisingly, has a very important role to playin environmental monitoring. GIS is ideally suited as atool for the presentation of data derived fromdistributed measurement stations (e.g. field-basedwater quality sensors). Unfortunately, however, mostGIS have some severe shortcomings when itcomes to dealing with the typical data obtainedfrom such measurements, namely time series data.The techniques for dealing with time series dataare covered more thoroughly elsewhere(Peuquet, Chapter 8). In a nutshell, time series arelong consecutive runs of data, such as thetemperature measured every half hour at a certainpoint. Since most standard GIS software packages donot possess adequate tools for handling temporaldata, they must be extended or auxiliary applicationsinterfaced. For a discussion of the approaches tointegrating GIS and external software systems seeAbel et al (1994); Federa and Kubat (1992);Goodchild et al (1992); Maguire (1995); Steyaert andGoodchild (1994).

The time series data routinely collected forenvironmental monitoring very often have twosignificant analytical and display problems. First,they typically relate to points, when data based onareal units would often be more useful (a problem ofspatial object type). Second, the temporal samplingincidence is often too frequent, resulting in largevolumes of data. GIS offer relatively simple meansof dealing with each of these problems. First, withregard to spatial resolution, a measurement pointmay be permanently assigned to a representative

area using a simple point-to-area transform(see Martin, Chapter 6), such as those based onThiessen tessellations (Boots, Chapter 36). Adifferent option is to use standard GIS gridding andcontouring facilities to interpolate between the pointmeasurements across the whole study area. Second,with regard to temporal resolution, standarddatabase selection capabilities may be used to extractdata pertaining to a time value corresponding toother data to which it must be compared.Alternatively, standard descriptive statisticalfunctions may be used to reduce data volumes(e.g. calculation of the average or maximum valuesfor characteristic periods: see Anselin, Chapter 17,for an overview of a full range of exploratory spatialdata indices). Any of these approaches may be usedalone, or in combination.

The data flow and hardware configuration for acombined monitoring and GIS is shown inFigure 1. The illustrated system is a rather complexexample implemented as a multi-user, client-serverconfiguration. Apart from showing the basic systemarchitecture, the figure also demonstrates howmany functions may be involved in a GIS-basedmonitoring system. In particular, it should be notedhow much of the system is actually dedicated tocollecting, processing, and storing data rather thanexplicit spatial analysis and display operations.Essentially GIS is only used at user workstations,whereas the major part of the system is dedicatedto other tasks. This distribution is in most casesreflected in the corresponding implementation andrunning costs. As a rule of thumb at least 90 percent of the cost involved in setting up anenvironmental monitoring system is related to themeasurement program, the quality control, andprocessing of data; only a minor part is related tothe programming of GIS-based analysis anddisplay functions.

Often the simple data analysis functions providedby standard GIS software packages are insufficientfor dealing with the data monitoring requirements ofenvironmental problems. The reasons for this aremany, the most common being:

● the economic aspects of a project do not allowsufficient data to be collected to ‘feed’ theanalysis tools;

● the characteristics of the data make simpleextrapolation inappropriate;

● several parameters are interconnected and therequired data cannot be measured directly.

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In such cases more complex models are needed toreflect the expected environmental situation. In suchcircumstances, the task of environmental monitoringgoes much further than can realistically be achievedwithin a standard GIS.

4 ENVIRONMENTAL MONITORING ANDMODELLING

Environmental monitoring operations are typicallyvery expensive to set up and maintain. Budgetconstraints often mean that monitoring

programmes have to be scaled down and that manysystems are barely adequate to meet theirobjectives. Chemical parameters, for example, arefrequently of interest to those who study theenvironment, but unfortunately appropriatemeasurement instruments for such parameters areoften very expensive to purchase and maintain.

One possible solution to this problem is tocombine a reduced field-based monitoringprogramme with mathematical modelling. Mostoften the elements of interest (chemicals, oxygen,sediment, smog, etc.) will behave in their carryingmedium (water or air) in a very specific way that

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Fig 1. Data flow and hardware network for an example environmental monitoring and assessment system.

Laboratory data entry and QC

Monitoring control Mathematical modelling Workstation User PCs

NT SQL and file server

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Database withQuality

ControlledData

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may be simulated. By setting up a mathematicalmodel describing the dynamics of the carryingcomponent (the water or the air flow) and bymonitoring the parameters of interest close to thesources (and, perhaps, other control points) verygood estimates of concentrations covering thecomplete area of interest can be obtained.

As an example, a project measuring, for instance,nitrogen concentration using hundreds of sensorscovering an entire area, may be transformed into thefollowing combined monitoring/modelling programme:

● monitor the driving forces for the dynamics, likeatmospheric pressure, wind velocity and direction.Such parameters can usually also be monitoredwith rather inexpensive yet reliable equipment;

● establish a mathematical description of the flowin the area, as a mathematical model;

● monitor the parameter of interest (nitrogen) at afew strategic locations, usually close to possibledirect sources and near model boundaries;

● by introducing the nitrogen in the model andusing the proper advection/dispersion or similarschemes in the calculation, the complete patternof concentration may be calculated.

While such an approach of course introduces anumber of uncertainties, it will in many casespresent a cost effective alternative to puremonitoring by means of sensors; indeed in somecases it may be the only viable alternative.

5 GIS AS AN ANALYSIS TOOL FORMONITORING DATA

Much too often the use of GIS for environmentalmonitoring is restricted to the presentation of dataand the creation of ‘pretty maps’. The inherentpowers of GIS as a tool for data integration andanalysis are very often underutilised.

The fact that monitoring systems often stop thedata analysis process when adequate quality controlof the incoming data has been performed prevents,for instance, environmental authorities from usingGIS to do further investigations of the causes ofpollution. Hopefully, the creation of more and moredatabases with spatial information will graduallychange this so that information on, for example,industrial development may readily be combined ona more ad hoc basis than is the case at the moment.

The ability to aggregate data from various inputsand present them in map form is a very importantmethod of strengthening general awareness ofenvironmental conditions. GIS is also a valuable toolin the decision-making process. Those who use GISto present environmental data as maps or graphsclearly need to be aware of the issues associated withclassification, symbolisation, and visualisation, notleast because they can affect the conclusions peopledraw about the data. This important subject iscovered elsewhere in this book (see Kraak,Chapter 11; Weibel and Dutton, Chapter 10).

6 EXAMPLES OF MONITORING SYSTEMS

6.1 Real-time monitoring

The Ringkøbing Fjord, a lagoon area in the westernpart of Denmark, is linked to the North Sea by anarrow channel with a sluice gate. The biotope insidethe lagoon is highly sensitive to environmentalpressure. The two most important parameters of thewater inside the lagoon are its oxygen and salinitybecause they fundamentally affect which species willthrive. The main (controllable) cause for changes tothese conditions is the inflow of seawater to thelagoon. An inflow which is too large may cause asalinity increase, whilst too little may cause oxygendepletion. The sluice gate in the channel connectingthe lagoon to the open sea may be used to control thisinflow. Both economic and environmental interestsare at stake in the Fjord and there is constant debatebetween farmers, wildlife experts, and fishermen.

The UNIX-based XDISP monitoring system(Plate 64) has the dual purpose of documenting thestate of the environment and functioning as an alarmsystem should a critical situation arise. The system usesa specialist software program to collect data on currentvelocities, water temperature, conductivity, and oxygen.This is achieved by carrying out background taskswhich are scheduled to communicate with thespecialised data collection hardware. Data collectedusing this process are fed into a GIS database whichorganises and stores the data.

For calculation of the complete patterns of oxygenconcentration and salinity, the system uses acombined modelling and monitoring strategy.Because of the real-time requirements of the system,it is not possible to run a full mathematical simulationmodel to support the measurements. Instead adatabase with a large number of characteristic flow

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patterns has been created using a mathematicalmodel. For each point in time the combined set ofmeasurements is taken and compared with thedatabase results using a pattern matching algorithm.The best matching flow pattern is then extracted fromthe database and used for further calculations toproduce the final concentration map. This methodmay be used in areas where certain fixed patterns offlow are always present.

By using the GIS capabilities the present state ofthe important parameters may always be evaluatedin close to real time. This approach also allowscomparison with historic measurements thusproviding an excellent basis for further discussion.For instance, the present situation can be compareddirectly with historic events that have resulted inwell-known consequences to the flora and fauna ofthe lagoon. As the system provides very highresolution results even very local phenomena, likeconditions in a fish farm, may be evaluated.

6.2 Local area monitoring

6.2.1 BackgroundEAGLE (Thorkilsen et al 1997) is a system used tocontrol the aquatic environment close to theconstruction site of a major bridge and tunnelproject. It is a very good example of how a GIScan be used in local environmental monitoring. Thesystem has been developed for Øresundskonsortiet,who are responsible for the construction of the fixedlink between Denmark and Sweden, a combinedbridge and tunnel crossing the Øresund Sound. Thesystem is part of a wider project concerned with thedevelopment of an environmental information andmanagement support system for Øresund.

In the construction phase of the fixed link, a largenumber of environmental issues concerning themarine environment must be monitored andevaluated. The state of the ecosystem is one of themost important parameters in management decisionsabout dredging and reclamation work. Data suchas hydrographic parameters, sediment transport,eelgrass growth, mussel coverage, fish migration,water quality, and bird life are taken into account inassessing the status of the environment. The EAGLEsystem contains information about the present stateof the ecosystem and interacts with a forecastmodelling system. Together these componentsare used to evaluate various construction scenariosin order to balance economic and environmentalinterests.

The EAGLE system monitors a large variety ofdata online. It receives results from backwardprojections and forecasting models and evaluates theresults against a large number of environmentalcriteria. In the event that constraints are violated, aseries of actions is triggered. The events and actionsare saved by the system for later analysis and asdocumentation for the authorities.

The information system part of EAGLE is used bythe authorities and other interested parties to monitorthe progress of the project and to follow the decisionsand field observations closely. EAGLE is constructedusing ESRI’s ArcView GIS, together with otherspecific-purpose programming tools. The main part ofthe system runs on PC hardware, employing bothlocal and wide area network technology.

6.2.2 Project descriptionConcern about the long-term environmental effectsof increased sedimentation and reduced water flowbetween the North Sea and the Baltic has led toextensive dredging to compensate for the blockingeffect of the bridge construction. Unfortunately,such large dredging operations may have severeimpacts upon the local environment. To avoid this, thelegislation covering the project has included dredgingperformance criteria and a complex monitoring andcontrol programme has been established. The EAGLEsystem is part of this procedure.

6.2.3 Environmental issues and requirementsDuring the construction, the major environmentalconcerns relate to the area where about 7 millioncubic metres of mainly clay and chalk-based seabedis being dredged. This has resulted in extensivesediment plumes in the shallow water areassurrounding the construction site itself.

An extensive environmental assessment concerningboth the local and global effects of the link was carriedout prior to the design of the bridge, but as suchassessments need to be done using the conditions of aso-called ‘normal year’ there is nothing to ensure thatthe conditions simulated during the assessment will besimilar to the actual conditions. This is particularlytrue for the construction phase which covers a four-year period only. Because of this uncertainty, intensivemonitoring is needed during development and anorganisation must be ready to evaluate the results andto take remedial action on a very short timescale inorder to avoid permanent damage to the environment.The more sensitive parts of the local environment

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concern the land-based fauna, the marine flora, andthe marine fauna of the area. The bridge willeventually border a major wildlife protection area.

The two governments involved and thecorresponding environmental protection agenciesexpressed a number of fairly general criteria whenauthorising the work. One example criterion is thatduring construction the biomass in the area may notbe reduced by more than 25 per cent. Obviouslysuch parameters cannot be controlled on a day-to-day basis and, consequently, the daily control has tobe done on simpler and more pragmatic criteria,referred to as ‘operational criteria’.

The operational criteria have been chosen in sucha way that they are relatively easy to transform intothe general criteria of the project. As an example,eelgrass has been chosen as a central plant tomonitor as it is an important part of the ecosystemin the area and it is sensitive to sedimentconcentrations in the water. In a similar fashion, alarge number of other criteria have been establishedwhich may be evaluated on the basis of measurementsand put into a monitoring programme.

6.2.4 Monitoring programmesIn order to control the environmental impactdirectly and provide sufficient information tosupport remedial actions at short notice, a numberof monitoring activities are performed on a routinebasis. The project involves four differentmonitoring programmes, all supplying data to theEAGLE system where results can be evaluatedand compared:

● Background monitoring: mainly hydrographicdata, such as water levels and currents, aremonitored constantly in order to maintain acomplete background profile of the hydrographicand meteorological conditions in the area.

● Spill monitoring: constant monitoring of thesediment plumes is being carried out on a 24 hourbasis. These data are used when reporting on spillquantities and form input to the sedimentmodelling process.

● Feedback monitoring: continuous monitoring ofthe key operational criteria is carried out toevaluate their usefulness.

● Control monitoring: overall qualitativemonitoring is carried out to register any possiblyunforeseen effects.

6.2.5 ModellingSeveral of the monitoring activities are combinedwith modelling activities. The following models runon a routine basis in the system:

● Hydrodynamic modelling: DHI-MIKE 21(Warren and Bach 1992) models the completehydrodynamic regime of the area in twodimensions. The results are used as input for thesediment transport model.

● Sediment transport modelling: the sedimenttransport and the sedimentation are modelledusing a combination of MIKE21PA and MIKE21MC standard models. These models input themeasured and budgeted spill from the dredgingoperations.

● Eelgrass growth: using the output from thesediment model the shadowing effect causing theeelgrass growth to slow down or stop is calculated.Combining this with other parameters, like waterdepth, natural light, temperature, and nutrition,the expected effect of the sediment plumes oneelgrass growth is modelled.

The modelling activities are mainly run using‘retrospective forecasts’; for example the knownweather and other boundary conditions for theprevious period are used as an input to the model.The results of the model can then be used toextrapolate the relatively sparse measurements into atotal coverage of the project area.

At regular intervals the same models are used inforecast mode to provide an updated environmentalimpact assessment (EIA) for the completeconstruction period, using the measured data up tothe start of the modelling period. This procedure willgradually reduce the uncertainty of forecasts andthus provide an even better foundation for decisionson remedial actions. This will help avoid violation ofany of the consents given for the project.

6.2.6 Feedback loopAll results from the modelling and monitoringprogrammes are compared to a set of operationalcriteria to see if the results identify whether any criteriaare violated. In instances of violation, a predefinedaction, or set of actions, is triggered and reported inthe system. The criteria and the actions are organisedin an escalating loop as is shown in Figure 2.

A triggered action (normally the first action isintensified monitoring) will always produce a new set

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Fig 2. The feedback mechanism within the Øresund Sound monitoring model.

Spill monitoringresults

Terminator

Revise spill budgetCompare to 5%overall criteria

Exceeds morethan 25%

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Stop work andimplement spill-

reducing measures

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Update hindcastCompare to

weekly spill rate

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fish, and birds

Goto feedbackprogram for

eelgrass

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season

Compare to themaximum totaldredging limit

Revise spill budget

Compare tomax. limit per

countryRevise spill budget

of data which again can be checked against theperformance criterion. This will continue until eitherthe situation is proved to be normal, or – in the eventof serious danger to the environment – remedialaction (ultimately stopping the construction work)has been taken.

6.2.7 The EAGLE systemAs can be seen from the above description, theprocedures for environmental monitoring andfeedback are very complex and involve largevolumes of different data types. To assist theenvironmental decision-makers in achieving thenecessary overview of the system and to support theright decisions, the GIS-based information system,EAGLE, was created as an adjunct to the XDISPmonitoring system.

EAGLE is able to display relevant modelling,monitoring, and decision process data in aconsistent environment. The basic data flow ofEAGLE is illustrated in the EAGLE Main Menushown in Plate 65. A database based uponMicrosoft SQL-Server running under Windows-NTis constantly updated by the organisationsresponsible for environmental monitoring andmodelling, and is distributed from a central fileserver to a range of users.

Users can access EAGLE from either the localarea network or through a wide area network basedupon ISDN connections. An automatic programupdate is incorporated into the system. Wheneverprogram files or other files residing locally on theuser machines are updated, new files areautomatically transferred to the machines withoutmanual intervention.

6.2.8 Sub-systemsEAGLE comprises the following sub-systems:

● a feedback module which provides an easy andrapid overview of all the different criteriainvolved in the evaluation process – as illustratedin the instance of spillage in Plate 66;

● an overview menu for feedback evaluation;● an incident database, which logs every incident of

environmental importance;● a general presentation module which allows users to

carry out their own full environmental assessmentrather than rely upon conclusions drawn by otherexperts (individual interests and concerns may beinvestigated at a very detailed level).

Presentational information that may be extractedusing EAGLE includes the following:

● sedimentation: data on sediments in the water arecontained in the database and may be presentedas either concentration isolines or as curvesshowing measurements versus time;

● satellite images: remote sensing information(primarily in the form of satellite imagery) hasbeen added to track sediment plumes. Theseimages may in turn be compared withmeasurements and model result plots;

● bird statistics: studies of the wildlife in the areasaround the construction site result in statistics, suchas nest counts and size statistics. These data may bepresented using charts (e.g. bar and pie charts) ontop of the basic maps held in the system;

● coastal morphology: as a reference for the ‘before’situation, a study of the coastal morphology inthe area was carried out and documented withcoastline data and photographs. These data areall available online for reference;

● common mussels/sedimentation: the netsedimentation as measured and modelled is storedin the database and may be presented as separatelayers to be compared, for example, to theformation of the common mussel, a species thatwill easily be affected by extensive sedimentation;

● spill reports: a major cause of environmentalproblems in this particular project is the spillingof sediment during dredging and reclamation. Aseparate part of EAGLE is devoted to reportingthe direct monitoring of spills. This part of thesystem also reports the progress of theconstruction work itself. Reports made on a dailybasis are supplemented with weekly reportscontaining quality controlled measurements only.

7 CONCLUDING REMARKS

The current state of GIS in environmentalmonitoring remains very much focused on the factthat GIS is an ideal tool for producing ‘prettypictures’ which can also, to a certain extent, be usedas a programming tool for user interfaces. GIS isused to a much smaller degree as an activecomponent of environmental monitoring systems.As the field matures it is to be expected thatenvironmental monitoring and GIS will becomemuch more closely integrated. At the same time, GISare becoming more and more user-friendly, making

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them much more relevant as tools for non-GISexperts, such as senior managers and domain expertsfrom other professional areas (Egenhofer and Kuhn,Chapter 28).

Once data are collected and stored in well-organiseddatabases, the possibilities for well-designed GISapplications are tremendous, not only within onedatabase but also using combinations of differentnetworked databases. The rapid development ofnetwork technology will no doubt also stimulate thedevelopment of distributed databases (Coleman,Chapter 22). New GIS products are now Internet-aware and, together with advances in spatial databasetechnology, possibilities exist for creating dynamicsystems able to perform operations on distributeddatabases. Applications based on technologies such as‘data drilling’ are now possible over the Internet. Thesetypes of application will be less and less sensitive to theoriginal purpose of the database being queried(Goodchild and Longley, Chapter 40).

The trend towards network technology is alsointeresting because it offers the possibility for dataaggregation. Almost all active environmentalmonitoring systems are local or regional systemsaimed at monitoring specific components of theenvironment and helping to solve specificenvironmental problems. One consequence of therise in environmental awareness is the need for exactinformation, as this is the only way for scientists andauthorities to evaluate the most appropriatemeasures and regulations. In such situations it willbe invaluable to be able to extract information fromthe increasing number of local monitoring systemsand to aggregate that information into moreglobally-oriented monitoring systems (see Wilson,Chapter 70).

To achieve such a level of integration andcorporation, a high degree of standardisation isrequired to be in place. Since almost all monitoringsystems are established by government authorities(or by requirement of a government) astandardisation effort should have a good chance ofsuccess at least at a national level. By formingstandards for how systems communicate on thenetwork and how measurements are specified, withrespect to quality, measurement method etc., it willbe possible to utilise monitoring results made locally

for other more general purposes in a larger scalemonitoring effort (Chapal and Edwards 1994).

All in all, GIS will be a component of everyenvironmental monitoring system within the nextfew years. This is quite simply because this type ofdata calls for the utilisation of GIS capabilities, andwhen one considers that GIS is becoming simpler touse and much cheaper to buy, it is hard to imagine afuture for environmental monitoring systemswithout it (Schroeter and Olsen 1996).

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Thorkilsen M, Dietrich J, Larsen L C, Nielsen A 1997Environmental and geographical information system fordredging control. Proceedings CEDA dredging days 1997.Central Dredging Association: 109–17

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