978-1-4244-8551-2/10/$26.00 ©2010 IEEE 1 ICIAfS10

Abstract- We present an effective solution for both digital map generation and real time user tracking for teams operating in hazardous environments or unfamiliar territory. The system is based on the client server model, where the client is a GPS enabled mobile phone which is capable of capturing coordinates and serving dynamic maps to the user. The maps plot the team’s navigational routes and enables real time tracking of each other. The server builds a GIS at the back end based on the data sent by the users, and also develops maps on demand. The system is implemented with simple hardware and uses the available GPRS network for data gathering. This enables the system to be used both in hazardous environments and by the general public.

I. INTRODUCTION

ncient drawings from great civilizations provide examples of human thirst for up-to-date information around the globe. Even in the Dark

Ages the information gathered by the primary mediums was often used in conquest, trade and expeditions. Today with the rapid development of information technology the paper based maps have transformed into digitalized form, providing much more information than just longitudes and latitudes. They are known as Geographical Information Systems (GIS) which support a number of functions and analysis that could be performed on location data. Real Time user tracking has also gathered momentum with the wide usage of GPS devices. This has gone beyond simple tracking, allowing a set of users to share information in real-time. One intended application of the proposed system is for rescue teams in hazardous situations who may want to navigate through unfamiliar territory while sharing information between members of a team. The concept of multiple user team tracking and path identification provides a mechanism for navigation

and information sharing, enabling team mates to view their subordinates, enables a better coordination between the team in such environments.

Creating a digitized map is usually a tiresome process where a cartographer will have to physically go over the area, capture the data and then manually enter it to create the GIS. Most often the creation of such digitalized map consumes thousands of dollars which prevents the usage of GIS by the general public. When it comes to hazardous environments like floods, landslides and earthquakes creation of digitalized maps require a more efficient process as the older maps are no longer usable[1][2].

With the rapid development of the mobile device technology, people are offered high computing power while on the move. This advancement has enabled the mobile devices with the capability to process medium scale applications in addition to mobile service provision. The Geographical Positioning System (GPS) enabled mobile devices have revealed a new dimension for real time user tracking, navigation, path identification and real-time map generation [2][3]. This has lead to the concept of a Mobile based GIS.

A Mobile Phone GIS Based on Mobile SVG (Scalable Vector Graphics) [3] had been purposed to address the need for a map application for heavily resource constrained hand held devices. They have highlighted the usage of SVG [4] as a map format for mobile and hand held devices as map processing is a highly resource consuming process. Mobile Mapping Applications over J2ME Enabled Phones[5] have been conducted where the final outcome has been Java 2 Mobile Edition (J2ME) -Based Mobile Mapping application (JMMA). JMMA shows that geographical information and mapping applications can be effectively delivered over J2ME-enabled

Deneth Karunarathne◊ and Thanushka Gunasekara+

Faculty of Information Technology, University of Moratuwa,

Moratuwa, Sri Lanka. Email: ◊deneth9@gmail.com

Email: +thanushkag@gmail.com

Dileeka Dias Department of Electronic and

Telecommunication Engineering, Faculty of Engineering, University of Moratuwa,

Moratuwa, Sri Lanka. Email: dileeka@ent.mrt.ac.lk

Dharshana KasthurirathneDialog-UoM Mobile Communications

Research Laboratory, University of Moratuwa,

Moratuwa, Sri Lanka Email: dkasthurirathna@gmail.com

Mobile Based GIS for Dynamic Map Generation and Team Tracking

A

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mobile phones that have limited capabilities. JMMA which is a client/server network application runs on a user’s mobile phone and connects to an Internet enabled database server machine via a wireless connection. This highlights an architecture that could be used for the proposed mobile based GIS.

A four tier client server GIS architecture with a four tier distributed architecture for mobile GIS is proposed in [6].This consists a of mobile client level, a top web service level, a GIS transaction level and a database level. Compared with the three tier client/server architecture, this adds the first web service level.

A NASA-funded research project [7] that focused on the development of mobile GIS tools and wireless Internet Map Server (IMS) services to facilitate environmental monitoring and management tasks have been tested recently. Though this project does not cater to route identification, it provides a real life experience with its prototype[8]. By developing and testing wireless web-based map/image servers, mobile GIS applications, and GPS, this research has created an integrated software/hardware infrastructure for a prototype mobile GIS application. This paper proposes a novel Mobile based GIS which enables team tracking and path identification while generating digitalized maps using the captured data.

Another Mobile GIS application had been tested in archaeological survey [9]. The objective of this application was to rapidly locate your starting position and line up your survey crew accordingly. This system was once again implemented using the commercial application ArcPad 6.0 [10] as it provides the basic functionality. This prototyped system once again demonstrates the requirement for a highly adaptive system which enables team tracking and route identification.

Further research was carried out on Scalable, distributed, real-time map generation [11]. Though this research does not carry a mobile device yet it talks of dynamic map generation from the data collected in real time using GPS receivers fixed in vehicles. The objective of the project has been to generate road maps based on the information collected from multiple vehicles. The application is based on the algorithm to transforms GPS traces from multiple vehicles into a road map. This is done by generating a 2D histogram indicating the number of GPS fixes found in each cell. Then the algorithm deduces the edges’ positions. Then it identifies the roads and the centerlines and the direction of travel. The research produces an insight on modeling route information.

Real time map generation and route identification using geo-spatial data is vital in disaster and emergency situations where digital maps are not available or where they are no longer useful. It is vital for relief teams to share their information and navigating routes with the follow-up teams. Assembly points and worst hit areas should be shared upon to provide adequate relief aid in times of a disaster. The system could be effectively used as map generation tool and a route sharing tool in such situations. The relief teams can view the routes already taken by other teams via their mobile devices. Their own navigational route will be visible as well. The system will provide both navigational information and disaster specific data between the respective parties. In addition it will provide the basic spatial data for novel map generation of the specified area

Key issues and the proposed solution are presented in Section 2. Section 3 describes the technologies used in the proposed system. In Section 4, the design approach of the proposed solution is presented. Design of the system is described in section 5, which is followed by the conclusion.

II. OVERVIEW OF THE MOBILE BASED GIS

Availability of Geographical Data in Digital format is a very vital need in the society which has roots in many industries including transportation, education, medical, military, etc. The research was initialized with the mindset of developing a low cost, reliable, efficient, effective and real-time means for collecting and processing Geographical Data in Digital format.

The Objective of the mobile based GIS is to implement a cost effective map generation framework using the available GPRS network and the available Open Source GIS software. In addition it will provide functionalities for real time user tracking, team tracking and path generation.

The mobile based GIS is composed of two sections: The client side and the server side. The client side is responsible for collection of data and displaying of the routes of the user and his subscribed teams. The server side is responsible for the processing of information and generation of maps, team management, route identification and serving of information for the subscribed users. The server contains an array of mapping functions which enable it to provide up-to-date information to the user.

The system enables a subscribed client with a GPS enabled mobile device to connect to the system and view his current navigational route, find the navigational routes of his teammates who are

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subscribed to the system. The user may has the capability to view all the paths drawn in the area of his navigation based on his privilege level. The user will be viewing his navigational route from his mobile device using the mobile client.

Apart from the navigational perspective, the system could be used as a tool to capture geographical information and send to the server Custom information such as images, and citations could be added with position information. This reduces the hassle of manual data manipulation which limits the error rate to a minimal value.

Finally the captured data will be saved in a database. With time, the users may witness developing of more and more information on their navigational routes. With multiple users using the system and based on the information available the system will function as GIS and provide a cost effective mechanism for map generation, team tracking and navigation.

In addition, a central command and control console is implemented to control all the users and their privileges.

III. ARCHITECTURE OF THE MOBILE BASED GIS

The system uses a basic client server architecture. The mobile client will capture the relevant data. The captured data is sent via the GPRS network to the server. Therefore the system does not require a separate communication infrastructure. The requests are sent using HTTP requests over the GPRS network. Figure 1 illustrates the communication architecture.

Fig. 1. Communication architecture.

The usage of the available GSM network provides a cost effect communication methodology.

The server is responsible for the mapping functions which will be executed based on the user requests. Once a request is processed the server will send a response to the user. Based on the response the client will display the received information. Figure 2 illustrates the modules and architecture of the system.

Fig. 2. The high level implementation architecture of the Mobile GIS.

IV. TECHNOLOGY CHOICES FOR THE MOBILE BASED GIS

Since J2ME-Based Mobile mapping applications have proved to be successful, the client application was implemented as a J2ME [12] application. The usage of a Java application at the front end enables a mobile device which uses Java support to function as a client of the system.

The backend of the system was completely developed using java as a spate module to be run inside the Geo Server [13]. The usage of Geo Server prevented the usage of a spate application server. In addition the module could directly use the libraries available in the geo server. This provided a great flexibility in setting up the system and running it. The geo tools [14] library was used in creation of the maps due to its effectiveness.

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The SVG and Portable Network Graphics (PNG) [15] formats were used to display the generated maps. Both these formats proved to be light weight. However, SVG is preferred as it provides much functionality for other mapping functions such as ability to embed data to a SVG file, light weight, uniform format.

Freely available shapefiles of the area denoted by the following coordinates [80.603337333333 W, 8.0801666673333 N], [80.503337333333 W, 8.0701666673333 N].

In addition some geo referenced raster maps were also used. The raster maps were generated by geo-referencing some downloaded Google road maps [16] and few standard 1:50000 maps. All these maps were available in the Geotiff format.

The entire application was based on the available Open source GIS software and free available maps. Therefore the system was built with minimum cost

V. OPERATIONAL LEVEL FUNCTIONALITIES

A. Mobile Client Operational Level Functionalities

The mobile client consists of several modules. Each module works collaboratively with the others to achieve the intended functionality of the mobile client.

The main functionality of the mobile client is to display retrieved maps from the server, collect GPS coordinates and send the GPS coordinates to the backend server, collect geo-spatial data and enabling the mobile client to manipulate it. In addition, the mobile client also provides the basic mapping functions zoom, pan, point and extra information. The mobile client handles all the graphical representation of data, thereby allowing the users to communicate with the back end server.

1. Map viewer

This module is mainly responsible for displaying the processed map to the user, handle user inputs to the map, provide required facilities to manipulate the map, and provide effective map viewing options. This module is also responsible for handling the interaction level user requests.

2. GPS collector

The mobile client runs a separate module for capturing of GPS data. This module is responsible for collecting GPS coordinates, averaging it, checking for accuracy of the readings and if the GPS coordinates are different from the previous reading, then send them to the server. This module may run

in anonymous mode where there are no user interactions or in the active mode where the user may interact.

3. XML Parser

This module is mainly responsible for converting incoming XML objects , generating the raster image and passing the raster image to the Map Viewer module for displaying. SVG AIP has been implemented to convert the incoming XML message and to generate the vector image.

4. Connection handler

The connection handler’s functions include handling the connection with the Server, handling the data transmission /receiving and finally maintaining a cache. Therefore the system can be operated even when the connection is temporarily unavailable.

B. GIS server Side

The server module implementation is illustrated in Figure 3.It was implemented as a GeoServer module whereby it could run inside the GeoServer. The module uses the Post-GIS database as the back end database to store the geo-spatial data. It manages the users and also their teams. Based on the request the relevant response will be transmitted to the client. The server module is implemented as a set of layers and modules as illustrated in Figure 3.

This Figure 3 illustrates the intercommunication between the modules and the layered mechanism of information passing. Each layer will manipulate the data and an object will be passed to the layer below. The same process will take place in the opposite direction when a message is sent. Each layer handles a specific task in the process

Fig. 3. The back end architecture

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A web interface is provided, from which a privileged user can see the progress of the team members, check navigational routes of the teams, check the generated maps, create teams, add team members, remove team members, etc using the web interface. The web interface is also hosted inside the GeoServer preventing the need for a second web server. The web application acts as a central command and control interface. With the use of hosted web-based systems, the system could be accessed irrespective of the geographical location.

1. Map Processor Service Module

This is the main module of the backend as it will be exposed to the outside. Therefore the methods declared in this module can be invoked form a remote client application. The module communicates via HTTPRESPONSES and HTTPREQUETS. As the module works with high-level protocols, any client which supports it can call the methods and access the functionality. The service can be assessed by a variety of web applications and also through the browser, given the methods and its argument types.

2. The communication Framework and Handling Requests

The communication framework is handled by java servelets. The map processor service module is itself a servelet. The class inherits form HTTPSERVLET , and the module provides all the functionality of the servelets to be dealt with. The clients will have to call the URL of the necessary service to gain the service offered. The input data for the method will be sent embedded in the URL. Both get and post methods are supported.

3. Handling Data

Handling data is one major component of the application. There are two verities of data. First the data stored in the PostgreSQL database & stored in shapefiles. This data includes user information, team information and recently updated data. The updated data is stored as points for easy retrieval. The second is the data transmitted from the clients who include coordinates, location descriptions and special tags to identify special locations as schools temples and structures of value

VI. TESTING THE SYSTEM

The testing of the system was carried out in the following environments:

A. Route Identification Test

The table 1 depicts the configuration for the test run which obtained the results shown in Figure 4.

TABLE I SYSTEM CONFIGURATION FOR TEST CASE

Configuration type Test values

System Configuration: Windows XP 2002

0.99 GB of Ram/ Intel 2.8 GHz Processor

Geo Sever Version GeoServer 1.7.0 /

Database Version PostgreSQL 8.3

Base Maps \Coordinates

Geotiff map of Moratuwa Area

[80.603337333333 W, 8.0801666673333 N],

[80.503337333333 W, 8.0701666673333 N].

Mobile Device: Nokia 6120 classic java enabled phone.

Data entering Mode: Manual

UserID 94010

TeamID 001

The Table 2 contains the URL which was called form the user application in order to achieve the results depicted in figure 4. Based on the location of the application the client will update the currentLoc field in the URL. This could be manually called if the user needs to share any specific data.

TABLE 2

URL FOR TESTING THE SCENARIO

Test case URL

http://112.135.192.48:8080/geoserver/ows?userid=94010&teamid=001&requesttype=2&currentLoc=80.57033373333,8.075116667&request=getUserPath&service=mobileMapProcService&version=1.0.0

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Fig. 4. Map resulting from test. The green lines demonstrate the path of navigation.

Figure 5 shows another test result run in the Colombo 6 area.

Fig. 5. Resulting map of a test conducted in the Colombo – 06 areas.

B. Map Creation Test

This test is carried out to verify that the maps are created correctly and that they can be viewed correctly in different platforms. This was done by plotting an already known location sequence in the map and cross checking it with the available data. Another verification test was done by saving the created map as a shapefile. Once the location information was sent, the map was created as a shapefile. Then it was reopened by Quantum GIS. The created map could be loaded successful and viewed correctly in third party applications.

Created SVG images are viewed by multiple clients. It was checked with both Firefox and Internet Explorer browsers. The SVG maps were also viewed with Mobile phone simulators. In some mobile simulators the SVG couldn’t be rendered. It was due to the fact some simulators do not support some of the SVG tags. So that implied the responses won’t work in such devices.

VII. CONCLUSIONS AND RECOMMENDATIONS FOR FURTHER

WORK

Dynamic map generation and route identification using real time geo-spatial data is vital in disaster and emergency situations where the original maps are not available or where they are no longer is useful. In addition, with the user and team tracking capability it caters to a wide array of users including rescue teams, scientific expeditions and archeological survey. The difference the system brings is it caters both locations tracking and map generation at the same time.

We have successfully implemented functions such as location tracking, team management and the communication of the data to remote clients. The system is also capable of creating maps based on a user defined base point. This enables the user to view the area that he is currently navigating in. If the base point is not defined it will use the base point of the map.

The system should be developed further to be used in real scenarios. The communication between the mobile application and the GPS locater of a mobile device is problematic as there is no specific protocol. Most of the devices rely on vendor specific libraries or only extends the functionality to vendor specific applications.

The system had been tested with 20 users. However, with the increasing number of requests for map generation, the system showed signs of slowing down. Vector maps were used as the base maps. With the usage of raster maps the response time was

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reduced Therefore vector maps are preferred as the base maps for the system.

The adaptation of SVG is done due to its powerful capabilities such as the ability to embed data to a file, lightweight, uniform format etc. However, developing an SVG library based on the Tiny SVG specification [2] for the GeoServer could be taken as further work of the system. As the currently available library lacks the tiny SVG support, the created SVG images have a problem when it comes to displaying in a mobile.

In addition the system should be tested in a variety of mobile devices using a variety of mobile service providers to identify the communication bottlenecks and runtime problems.

ACKNOWLEDGMENT

The authors extend their appreciation to the staff of the Faculty of Information Technology, University of Moratuwa and Dialog-UoM Mobile Communications Research Laboratory, University of Moratuwa who extended their support in numerous ways for this work.

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