Web Map Services in Crisis Management

POSSIBILITIES OF WEB SERVICES IN RISK MANAGEMENT

Veroslav KAPLAN1, Jiri KOZEL2, Tomas REZNIK3, Zdenek STACHON4

, , ,

MasarykUniversity, Faculty of Science, Department of Geography,

Laboratory on Geoinformatics and Cartography

Kotlarska 2, 611 37 Brno, CzechRepublic

Introduction

The floods in the Czech republic in 1997 in Moravian region and in 2002 in Bohemian region showed that there are weaknesses in the decision making process. There are many ways how to speed up this process and make it more efficient. One of them is use of web services to provide online different type of information from different sources online. This attitude was tested on example of dangerous material transportation.

1.WEB MAP SERVICES

According to World Wide Web Consortium (W3C) Web Services Working Group:“Web service is a software system designed to support interoperable machine-to-machine interaction over a network.” [10]. Although W3C concentrates primary to the WSDL/SOAP web services (see web services definition in [11]), this somewhat broad description is still applicable for web map services.

Generally any software system which provides its data by HTTP access can be considered as Web service. As web services are often followedby automateddata processing,web services responses are usually provided in machine-readable format (such as XML).

In the field of geographic information systems, there are three main web services standards – Web Map Service (WMS), Web Feature Service (WFS) and Web Coverage Service (WCS). There also exists emerging standard of Web Feature Service Transactional (WFS-T). All these standards are published by Open Geospatial Consortium (OGC) and are royalty free.

2.MAIN FEATURES OF WEB SERVICES

2.1 Web services architecture

Web service deployment consists of setting up the server part, which responds to HTTP requests sent by clients and send them HTTP response. The request should specify parameters which are passed to the server, which parses them, process them and customizes the response according to the parameters of the request.

Figure 1.: Web Service (request/response) architecture.

There are three main geospatial web services standards

Web Map Service (WMS) – WMS standard defines way how to provide and retrieve rendered raster map from web map server. Final response of the service contains map rendered in raster file format (JPG, PNG, ...)

Web Feature Service (WFS) – WFS standard defines way how to provide and retrieve read access to spatial vector layers. Final response of the service is XML document containing attributes and topography of requested vector features.

Web Coverage Service (WCS) – WCS standard defines way how to provide and retrieve read access to spatial raster layers. Final response of the service is XML document containing raster data of requested area.

In addition, there also exists new standard Web Feature Service Transactional (WFS-T) which extends WFS possibilities to modify spatial objects – e.g. object adding, editing and deleting.

2.2 Why use web services?

Distributability- Because of Web services client/server architecture, it can be easily distributed in many interesting ways.

one data store / many clients scenario – implementing one centralized data store, it's easy to provide actual data to many users accessing web service,

Figure 2.: One data store many clients scenario.

aggregation – using layered web services it's easy to deploy “collect data at lowest possible level” principle. Data are collected at lowest possible level and aggregated to higher web servers,

Figure 3.:Aggregation scenario.

scalability – using several duplicated web services servers it's possible to transparently to distribute system load.

Independence on vendor - Web services standards are built on top of industry standards (HTTP, XML, SOAP), which provide independence on the platform and vendor.

Expandability - There exists a lot of XML related tools like DOM, XLST... These tools provide easy possibilities to develop own solution or extend existing ones.

Combining multiple sources - Web services make it easy to combine multiple data sources and it's possible to make analyzes on many data sets, each stored on different computer systems. As WMS/WFS/WCS standards are free, they can be used in any application/system.

Interoperability – Many commercial GIS products are able to interoperate using web services. Using remote web map services it's easy to deploy “one data store – many users” schema. Datasets can be stored in one data store system; thus, all users in one organization can use it. Using one centralized data store gains profit of easy system management. Centralized data stores makes also new data deployment and data administration easy.

3.CONTEXT CARTOGRAPHIC VIZUALIZATION

Classical maps are no longer appropriate for real time decision making process, because they cannot react on changing situation. We let our map to be generated online, influenced by Action (task, spatial extend etc.), Technology (device display size, transfer rate etc.), Situation (location, time etc.) and User (education, skills etc.). This map reflecting all of these influences is creating context[2, 3].

Cartographic visualisation can provide different type of outputs. Benefits of context approach are in representation of important information and suppression of marginal information. This approach is based on definition different types of contexts for various user and situation. User gets only information he needs in actual situation.

Figure 4. Context Cartographic Visualization

4.ADVANTAGES OF WMS IN DECISION MAKING PROCES

Emergency squads need relevant information about the crisis situation to improve their decision process. The information is necessary to be delivered as soon as possible and it must be understandable. This conditions are achieved by on-line access provided by using web map services and special map symbology delivered by contextual cartography.

Using web map services allows development team to create interoperable maps solution for emergency squads. Presented solution is vendor and operating environment independent. Web map services also make us possible to test and develop innovative cartographic solutions – eg. context cartography.

Figure 5. Web map service flow diagram (using context)

5.DANGEROUS MATERIAL TRANSPORTATION

Dangerous chemical substances transport is one of the most frequent dangerous activity, we can meet daily (see fig. 6). There were over eight hundreds of car accidents with leak of chemical substances in South Moravian region in 1997 – 2005. It means average 100 car accidents with leak of dangerous chemical substances per year only in South Moravian region. According to this fact it is very important to improve the possibilities of efficient action of rescue squads especially fire brigades in this case.

Figure 6.Number of car accidents in south Moravian region in 1997-2005 [9].

It was the main reasons why Concept of context cartographic visualization combined with providing online information by web services for emergency squads was tested on example of dangerous material transportation.

After process analysis there were identified four different contexts on dangerous materials transportation case study:

Context water –possibility of infiltration of rivers, watershed and other water sources

Context air – possibility of air pollution

Context fire – risk of dangerous fire

Context blast – possibility of explosion

For each context the important cartographic objects were selected. Topographic background is displayed only in greyscale allowing better perception of important thematic layer (see fig. 7).

Figure 7. Web map services deployment in dangerous transport case study

CONCLUSIONS

Testing of designed system on chosen example of monitoring of dangerous material transportation verified, that use of context visualization is useful and can improve and fasten the decision making process. Using web map services simplified testing and development of innovative cartographic solutions.On the other hand experiment showed weak parts of the system – eg. insufficient support of advanced map services features in common web map services implementations. Testing of chosen approach will be further developed and refined on other emergency management relevant scenarios.

This research has been supported by funding from Project of the Ministry of Education, Youth and Sports No. MSM0021622418 called Dynamic Geovisualization in Risk Management.

REFERENCES:

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[10]W3C Working Group, Web Services Architecture, online at

[11]W3C Group, Web Services Glossary, online at <