InformatIon ScIence Reference Part 7 ppt

Location-Based Services Time of Arrival (TOA): The position of a device can be determined by measuring the transferring-time of a signal between the device and the COO Ubiquitous Information Management (UIM): A communication concept, which is free from temporal and, in general, from spatial constraints Time Difference of Arrival (TDOA): Determining a more precise position information of a device by taking advantage of a cells infrastructure and measuring the transferring time of a device to three or more antennas Ultra Wideband (UWB): A technology which enables very short-range positioning information 276 277 Chapter XXXV Coupling GPS and GIS Mahbubur R Meenar Temple University, USA John A Sorrentino Temple University, USA Sharmin Yesmin Temple University, USA Abstr act Since the 1990s, the integration of GPS and GIS has become more and more popular and an industry standard in the GIS community worldwide The increasing availability and affordability of mobile GIS and GPS, along with greater data accuracy and interoperability, will only ensure steady growth of this practice in the future This chapter provides a brief background of GPS technology and its use in GIS, and then elaborates on the integration techniques of both technologies within their limitations It also highlights data processing, transfer, and maintenance issues and future trends of this integration INTRODUCT ION The use of the Global Positioning System (GPS) as a method of collecting locational data for Geographic Information Systems (GIS) is increasing in popularity in the GIS community GIS data is dynamic – it changes over time, and GPS is an effective way to track those changes (Steede-Terry, 2000) According to Environmental Systems Research Institute (ESRI) president Jack Dangermond, GPS is “uniquely suited to integration with GIS Whether the object of concern is moving or not, whether concern is for a certain place at a certain time, a series of places over time, or a place with no regard to time, GPS can measure it, locate it, track it.” (Steede-Terry, 2000) Copyright © 2009, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited Coupling GPS and GIS Although GIS was available in the market in the 1970s, and GPS in the 1980s, it was only in the mid1990s that people started using GPS coupled to GIS The GPS technology and its analogs (Global Navigation Satellite System or GLONASS in Russia and the proposed Galileo system in Europe) have proven to be the most cost-effective, fastest, and most accurate methods of providing location information (Longley et al, 2005; Trimble, 2002; Taylor et al, 2001) Organizations that maintain GIS databases – be they local governments or oil companies – can easily and accurately inventory either stationary or moving things and add those locations to their databases (Imran et al, 2006; Steede-Terry, 2000) Some common applications of coupling GPS and GIS are surveying, crime mapping, animal tracking, traffic management, emergency management, road construction, and vehicle navigation B ACKGROUND N eed for GPS D ata in G IS When people try to find out where on earth they are located, they rely on either absolute coordinates with latitude and longitude information or relative coordinates where location information is expressed with the help of another location (Kennedy, 2002) GIS maps can be created or corrected from the features entered in the field using a GPS receiver (Maantay and Ziegler, 2006) Thus people can know their actual positions on earth and then compare their locations in relation to other objects represented in a GIS map (Thurston et al, 2003; Kennedy, 2002) GIS uses mainly two types of datasets: (a) primary, which is created by the user; and (b) secondary, which is collected or purchased from somewhere else In GIS, primary data can be created by drawing any feature based on given dimensions, by digitizing ortho-photos, and by analyzing survey, remote sensing, and GPS data 278 Using GPS, primary data can be collected accurately and quickly with a common reference system without any drawing or digitizing operation Once the primary data is created, it can be distributed to others and be used as secondary data Before using GPS as a primary data collection tool for GIS, the users need to understand the GPS technology and its limitations The GPS Technology The GPS data can be collected from a constellation of active satellites which continuously transmit coded signals to receivers and receive correctional data from monitoring stations GPS receivers process the signals to compute latitude, longitude, and altitude of an object on earth (Giaglis, 2005; Kennedy, 2002) A method, known as triangulation, is used to calculate the position of any feature with the known distances from three fixed locations (Letham, 2001) However, a discrepancy between satellite and receiver timing of just 1/100th of a second could make for a misreading of 1,860 miles (Steede-Terry, 2000) Therefore, a signal from a fourth satellite is needed to synchronize the time between the satellites and the receivers (Maantay and Ziegler, 2006; Longley et al, 2005; Letham, 2001) To address this fact, the satellites have been deployed in a pattern that has each one passing over a monitoring station every twelve hours, with at least four visible in the sky all the times (Steede-Terry, 2000) The United States Navigation Satellite Timing and Ranging GPS (NAVSTAR-GPS) constellation has 24 satellites with spares orbiting the earth at an altitude of about 12,600 miles (USNO NAVSTAR GPS, 2006; Longley et al, 2005; Steede-Terry, 2000) The GLONASS consists of 21 satellites in orbital planes, with on-orbit spares (Space and Tech, 2005) The proposed system GALILEO will be based on a constellation of 30 satellites and ground stations (Europa, 2005) Coupling GPS and GIS The NAVSTAR-GPS has three basic segments: (1) the space segment, which consists of the satellites; (2) the control segment, which is a network of earth-based tracking stations; and (3) the user segment, which represents the receivers that pick up signals from the satellites, process the signal data, and compute the receiver’s location, height, and time (Maantay and Ziegler, 2006; Lange and Gilbert, 2005) Data Limitations and Accuracy Level Besides the timing discrepancies between the satellites and the receivers, some other elements that reduce the accuracy of GPS data are orbit errors, system errors, the earth’s atmosphere, and receiver noise (Trimble, 2002; Ramadan, 1998) With better attention to interoperability between the GPS units, hardware, and software, some of these errors can be minimized before the data are used in GIS (Thurston et al, 2003; Kennedy, 2002) Using a differential correction process, the receivers can correct such errors The Differential GPS (DGPS) uses two receivers, one stationary and one roving The stationary one, known as the base station, is placed at a precisely known geographic point, and the roving one is carried by the surveyor (Maantay and Ziegler, 2006; Imran et al, 2006; Thurston et al, 2003; Kennedy, 2002; Taylor et al, 2001; Steede-Terry, 2000) The base station sends differential correction signals to the moving receiver Prior to 2000, the GPS signal data that was available for free did not deliver horizontal positional accuracies better than 100 meters Data with high degree of accuracy was only available to U.S government agencies and to some universities After the U.S Department of Defense removed the restriction in May 2000, the positional accuracy of free satellite signal data increased to 15 meters (Maantay and Ziegler, 2006) In September 2002, this accuracy was further increased to to meters horizontally and to meters vertically using a Federal Aviation Administration funded system known as Wide Area Augmentation System (WAAS) WAAS is available to the public throughout most of the continental United States (Maantay and Ziegler, 2006) Depending on the receiver system, the DGPS can deliver positional accuracies of meter or less and is used where high accuracy data is required (Maantay and Ziegler, 2006; Longley et al, 2005; Lange and Gilbert, 2005; Taylor et al, 2001) For example, the surveying professionals now use Carrier Phase Tracking, an application of DGPS, which returns positional accuracies down to as little as 10 centimeters (Maantay and Ziegler, 2006; Lange and Gilbert, 2005) INTEGR AT ION OF GPS AND G IS The coupling of GPS and GIS can be explained by the following examples: • • A field crew can use a GPS receiver to enter the location of a power line pole in need of repair; show it as a point on a map displayed on a personal digital assistant (PDA) using software such as ArcPad from ESRI; enter attributes of the pole; and finally transmit this information to a central database (Maantay and Ziegler, 2006) A researcher may conduct a groundwater contamination study by collecting the coordinates and other attributes of the wells using a GPS; converting the data to GIS; measuring the water samples taken from the wells; and evaluating the water quality parameters (Nas and Berktay, 2006) There are many ways to integrate GPS data in GIS, ranging from creating new GIS features in the field, transferring data from GPS receivers to GIS, and conducting spatial analysis in the field (Harrington, 2000a) More specifically, the GPS-GIS integration can be done based on the 279 Coupling GPS and GIS following three categories – data-focused integration, position-focused integration, and technology-focused integration (Harrington, 2000a) In data-focused integration, the GPS system collects and stores data, and then later, transfers data to a GIS Again, data from GIS can be uploaded to GPS for update and maintenance The position-focused integration consists of a complete GPS receiver that supplies a control application and a field device application operating on the same device or separate devices In the technology-focused integration, there is no need for a separate application of a device to control the GPS receiver; the control is archived from any third party software (Harrington, 2000a) Figure provides an example of a schematic workflow process of the GPS-GIS integration by using Trimble and ArcGIS software In short, the integration of GPS and GIS is primarily focused on three areas - data acquisition, data processing and transfer, and data maintenance Figure Example workflow process of GPS-GIS integration Data Acquisition Before collecting any data, the user needs to determine what types of GPS techniques and tools will be required for a particular accuracy requirement and budget The user needs to develop or collect a GIS base data layer with correct spatial reference to which all new generated data will be referenced (Lange and Gilbert, 2005) The scale and datum of the base map are also important For example, a large-scale base map should be used as a reference in a site specific project in order to avoid data inaccuracy While collecting GPS data in an existing GIS, the datum designation, the projection and coordinate system designation, and the measurement units must be identical (Kennedy, 2002; Steede-Terry, 2000) It is recommended that all data should be collected and displayed in the most up-to-date datum available (Lange and Gilbert, 2005) The user may create a data dictionary with the list of features and attributes to be recorded 280 before going to the field or on-spot If it is created beforehand, the table is then transferred into the GPS data collection system Before going to the field, the user also needs to find out whether the locations that will be targeted for data collection are free from obstructions The receivers need a clear view of the sky and signals from at least four satellites in order to make reliable position measurement (Lange and Gilbert, 2005; Giaglis, 2005) In the field, the user will check satellite availability and follow the manuals to configure GPS receivers before starting data collection GIS uses point, line, and polygon features, and the data collection methods for these features are different from one another A point feature (e.g., an electricity transmission pole) requires the user Coupling GPS and GIS to remain stationary at the location and capture the information using a GPS device For a line feature (e.g., a road), the user needs to record the positions periodically as s/he moves along the feature in the real world To capture a polygon feature (e.g., a parking lot) information, the positions of the recorder are connected in order to form a polygon and the last position always connects back to the first one The user has to decide what types of features need to be created for a GIS map In a small scale map, a university campus can be shown as a point, whereas in a detailed map, even a drain outlet can be shown as a polygon GPS coordinates can be displayed in real time in some GIS software such as ESRI ArcPad, Intergraph Intelliwhere, and Terra Nova Map IT In the age of mobile GIS, users can go on a field trip, collect GPS data, edit, manipulate, and visualize those data, all in the field While GPS and GIS are linked, the GPS receiver can be treated as the cursor of a digitizer It is linked to the GIS through a software module similar to a digitizer controller where data are saved into a GIS filing system (Ramadan, 1998; UN Statistics Division, 2004) In real-time GPS/GIS integration, data may be collected and stored immediately for future use in a mapping application, or data may be discarded after use in a navigation or tracking application (Thurston et al, 2003) For example, Map IT is a new GIS software designed for digital mapping and GPS data capture with a tablet PC The software connects a tablet pc to a GPS antenna via a USB port While conducting the field work, the user may use the software to: (a) display the current ground position on the tablet PC’s map display in real time; (b) create new features and add coordinates and other attributes; (c) edit or post-process the data in real time; and (d) automatically link all activity recorded in the field (including photographs, notes, spreadsheets, and drawings) to the respective geographic positions (Donatis and Bruciatelli, 2006) Although the integration of GIS and GPS can in general increase accuracy and decrease project costs and completion time, it can also create new problems, including creation of inaccurate data points and missing data points (Imran et al, 2006) Sometimes a handheld GPS navigator may not be able to acquire a lock on available satellites because of natural conditions like dense forest canopies, or human-made structures like tall buildings or other obstacles (Lange and Gilbert, 2005; Thurston et al, 2003) Data collection with GPS also might get affected by any equipment malfunction in the field D ata Processing and T ransfer Once the data are collected, they can be downloaded, post-processed, and exported to GIS format from the field computer to the office computer Where real-time signals are needed but cannot be received, the post-processing techniques can be applied to re-process the GPS positions Using this technique, the feature positions can be differentially corrected to the highest level of accuracy The users who integrate GPS data into their own applications need to consider how and when they should apply differential corrections Real-time processing allows recording and correcting a location in seconds or less, but is usually less accurate Post-processing allows the surveyor recording a location as much time as s/he likes, and then differentially corrects each location back in the office This technique is used in mapping or surveying (Steede-Terry, 2000; Thurston et al, 2003) Instead of relying on real-time DGPS alone, the users should enable their applications to record raw GPS data and allow post-processing techniques to be used either solely or in conjunction with real-time DGPS (Harrington, 2000b) Most GPS receiver manufacturers have their own data file format GPS data is stored in a receiver in its own format and later can be translated to various GIS formats (Lange and Gilbert, 281 Coupling GPS and GIS 2005; Ramadan, 1998) Data can be transferred in a couple of ways One simple way is collecting coordinates and attributes in a comma delimited file from the GPS device storage The other more preferable way is converting the data from GPS storage to the user-specific database interchange format using a data translation program (Lange and Gilbert, 2005) Such a program allows the user to (1) generate metadata; (2) transform the coordinates to the projection, coordinate system, and datum of the user’s choice; and (3) translate GPS data into customized formats that the GPS manufacturers could never have anticipated (Lange and Gilbert, 2005) A number of file interchange protocols are available to exchange data between different brands and types of receivers One widely used interchange protocol is the Receiver Independent Exchange Format (RINEX), which is supported by most satellite data processing software (Yan, 2006) Another commonly used interface standard is a standard released by the National Marine Electronics Association (NMEA) Most GPS receivers support this protocol and can output NMEA messages, which are available in ASCII format (Yan, 2006) D ata Maintenance For data revisions or data maintenance, GIS data is transferred back to the field computer and can be verified or updated in the field The user can relocate features via navigation, verify the position and attribute features, and navigate to locations to collect new attribute data The user may select features and examine them in the field, modify attributes, and even collect new features if desired Using receivers such as Trimble, any feature that has been added or updated is automatically marked to determine which data needs to go back to GIS (Trimble, 2002) 282 FUTURE TRENDS The future trends of GIS-GPS integration will be focused on data accuracy, interoperability, and affordability In order to make the WAAS level of precision available to users worldwide, the Unites States is working on international agreements to share similar technologies available in other parts of the world, namely Japan’s Multi-Functional Satellite Augmentation System (MSAS) and Europe’s Euro Geostationary Navigation Overlay Service (EGNOS) (Maantay and Ziegler, 2006) In addition, the European satellite positioning system, Galileo, will be dedicated to civilian activities which will further increase the availability of accurate data to general users New applications of GIS-GPS integration are constantly becoming popular and widespread The latest developments in GPS technology should encourage more use of such integration in the future Reduction in cost and personnel training time of using GPS technology with high data accuracy will eventually provide a cost-effective means of verifying and updating real time GIS mapping in the field (Maantay and Ziegler, 2006; UN Statistics Division, 2004) CONC LUS ION In today’s market, the mobile GIS and GPS devices are available with greater accuracy at a reduced cost The data transfer process from GPS to GIS has become faster and easier GIS software is getting more powerful and user friendly, and GPS devices are increasingly getting more accurate and affordable The integration of GIS and GPS has been already proven to be very influential in spatial data management, and it will have steady growth in the future Coupling GPS and GIS REFERENCES Donatis, M., & Bruciatelli, L (2006) Map IT: The GIS Software for Field Mapping with Tablet PC Computers and Geosciences, 32(5), 673-680 Europa web site http://www.eu.int/comm/dgs/energy_transport/galileo /index_en.htm, accessed on December 12, 2005 Giaglis, G (2005) Mobile Location Services In M Khosrow-Pour (Ed.), Encyclopedia of Information Science and Technology, 4, 1973-1977 Pennsylvania: Idea Group Reference Harrington, A (2000a) GIS and GPS: Technologies that Work Well Together Proceedings in the ESRI User Conference, San Diego, California Harrington, A (2000b) GPS/GIS Integration: What Can You Do When Real-Time DGPS Doesn’t Work? GeoWorld, 13(4) Available online at http:// www.geoplace.com/gw/2000/0400/0400int.asp, accessed on August 25, 2006 Imran, M., Hassan, Y., & Patterson, D (2006) GPS-GIS-Based Procedure for Tracking Vehicle Path on Horizontal Alignments Computer-Aided Civil and Infrastructure Engineering, 21(5), 383-394 Kennedy, M (2002) The Global Positioning System and GIS: An Introduction New York: Taylor and Francis Maantay, J & Ziegler, J (2006) GIS for the Urban Environment California: ESRI Press, 306-307 Nas, B & Berktay, A (2006) Groundwater Contamination by Nitrates in the City of Konya, (Turkey): A GIS Perspective Journal of Environmental Management 79(1), 30-37 Lange, A & Gilbert, C (2005) Using GPS for GIS Data Capture In Geographic Information Systems: Principles, Techniques, Management, and Applications (pp 467-476) NJ: John Wiley & Sons, Inc Letham, L (2001) GPS Made Easy Washington: The Mountaineers, 5(12), 183-186 Longley, P., Goodchild, M., Maguire, D., & Rhind, D (2005) Geographic Information Systems and Science New Jersey: John Wiley & Sons, Inc (pp 122-123, 172-173) Ramadan, K (1998) The Use of GPS for GIS Applications Proceedings in the Geographic Information Systems: Information Infrastructures and Interoperability for the 21st Century Information Society, Czech Republic Space and Tech web site http://www.spaceandtech.com/spacedata/constellations/glonass_consum.shtml, accessed on December 12, 2005 Steede-Terry, K (2000) Integrating GIS and the Global Positioning System California: ESRI Press Taylor, G., Steup, D., Car, A., Blewitt, G., & Corbett, S (2001) Road Reduction Filtering for GPS-GIS Navigation Transactions in GIS, 5(3), 193-207 Thurston, J., Poiker, T., & Moore, J (2003) Integrated Geospatial Technologies – A Guide to GPS, GIS, and Data Logging New Jersey: John Wiley & Sons, Inc Trimble Navigation Limited (2002) TerraSync Software – Trimble’s Productive Data Collection and Maintenance Tool for Quality GIS Data California: Trimble Navigation Limited UN Statistics Division (2004) Integration of GPS, Digital Imagery and GIS with Census Mapping New York: United Nations Secretariat USNO NAVSTAR GPS web site http://tycho usno.navy.mil/gpsinfo.html, accessed on August 26, 2006 Yan, T (2006) GNSS Data Protocols: Choice and Implementation Proceedings in the International Global Navigation Satellite Systems Society IGNSS Symposium, Australia 283 Coupling GPS and GIS Coordinate System: A reference framework used to define the positions of points in space in either two or three dimensions GPS Segment: GPS consists of three segments: (i) space segment – the GPS satellites, (ii) user segment – the GPS handheld navigator, and (iii) ground control segment – the GPS monitoring stations Datum: The reference specifications of a measurement system, usually a system of coordinate positions on a surface or heights above or below a surface Projection: A method requiring a systematic mathematical transformation by which the curved surface of the earth is portrayed on a flat surface DGPS: The Differential GPS (DGPS) is used to correct GPS signal data errors, using two receivers, one stationary (placed at a precisely known geographic point) and one roving (carried by the surveyor) The stationary receiver sends differential correction signals to the roving one Scale: The ratio between a distance or area on a map and the corresponding distance or area on the ground, commonly expressed as a fraction or ratio key T er ms 284 WAAS: The Wide Area Augmentation System (WAAS) is a system that can increase the GPS signal data accuracy to to meters horizontally and to meters vertically 285 Chapter XXXVI Modern Navigation Systems and Related Spatial Query Wei-Shinn Ku Auburn University, USA Haojun Wang University of Southern California, USA Roger Zimmermann National University of Singapore, Singapore Abstr act With the availability and accuracy of satellite-based positioning systems and the growing computational power of mobile devices, recent research and commercial products of navigation systems are focusing on incorporating real-time information for supporting various applications In addition, for routing purposes, navigation systems implement many algorithms related to path finding (e.g., shortest path search algorithms) This chapter presents the foundation and state-of-the-art development of navigation systems and reviews several spatial query related algorithms INTRODUCT ION Navigation systems have been of growing interest in both industry and academia in recent years The foundation of navigation systems is based on the concept of utilizing radio time signals sent from some wide-range transmitters to enable mobile receivers to determine their exact geographic Copyright © 2009, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited A Package-Based Architecture for Customized GIS System administrator takes charge of controlling the server side adapting and updating the packages to the CBDS The case study that motivated this work stems from our interaction with the public administration, specifically the Infrastructure and Transport Department of a regional government authority This organization has more than 400 computers users, many of whom utilize GISs on a sporadic basis They commonly use proprietary desktop applications with high annual license payments However, according to internal surveys, many of these users require only a specific subset of GIS functionality Moreover, users are distributed geographically, so it is important to centralize the remote maintenance and the installation of the software in order to save time and money The architecture proposed here is valid for both commercial and free software, but additional monetary benefit naturally accrues for the case of GIS applications based on free software components (Anderson, 2003) Today, it is possible to reuse existing software libraries that cover the basic functionality of a GIS application, and in many cases source code is available so that these libraries can be modified or extended by system administrators Examples of these libraries are Geotools (www.geotools.org) and Terralib (Camara, 2000), which are distributed under the Lesser General Public License (LGPL) (GNU, 1999), so they are valid for open source developments as well as for commercial purposes re lated work The structure of the package-based architecture is directly related to the object-oriented frameworks (Fontoura, 2001) concept The main difference is that instead of a collection of smaller components, we implement a collection of higher-level packages with predefined collaborations between them and extension interfaces In order to connect each developed package to the kernel, it must apply the extension interfaces, and connect to the points of extension called hot spots (Pree, 1995) Our packages are pieces of software that implement a specific functionality, deployable as a unit of versioning and replacement The package contains immutable code, and metadata information necessary for connection to the kernel This structure must allow a dynamic recomposition of the software transparent with respect to the application source code Software components are well defined by Szyperski (1998) as binary units of independent production, acquisition, and deployment that interact to form a functioning system The most well-know component model is ActiveX/COM+ (Rogerson, 1997), an interesting model for Windows programming integration but not very interesting for dynamic composition Moreover, the option of programming custom solutions using ActiveX components is viable for groups of users, but not for individual customization In the field of GIS a widely-implemented example of CBSD is the ESRI MapObjects (Hartman, 1997) platform: an ActiveX control and a collection of dozens of automation objects that provide basic GIS and mapping capabilities These components must be embedded in an application development environment, such as Visual Basic, beyond the capability of typical GIS users and therefore the domain of end user composition We are interested in a higher aggregation of components (self-contained packages) that can be included into the main application without the need to modify the source code of the base system, and that can be maintained and updated centrally by the system operator Arch itecture over v iew In search of a low cost GIS solutions with an optimal level of functionality, we modify the traditional concept of a monolithic GIS application and redistribute it to better fit a changing corporative 313 A Package-Based Architecture for Customized GIS environment, one which is integrated in a highspeed network (100 Mbps LANs) The proposed architecture would not have been viable in most organisations 10 years ago, as shown in previous studies (Anitto, 1994) due to the inherent communication capabilities required The proposed architecture is defined keeping in mind two key system features: minimal system maintenance costs due to centralization and scalability of the system in a natural way, avoiding costly reengineering processes In order to achieve the desired flexibility, the system is separated into a kernel and a set of external packages The kernel implements the main thread of the system and is in charge of building the client side GIS application In this process, the requested packages are loaded in order to build the final application System maintenance is high-overhead cost, and so we follow Isnard (2004), in assuring that the system administration design also builds maintenance tasks into the computing environment The proposed architecture centralizes all software maintenance and distribution, by means of a central server that contains the packages for future composition of custom GIS applications C orporate N eeds in G IS After studying the existing solutions for Corporate Geographic Information Systems (CGIS), we have identified the following key factors to take into consideration: • • 314 Customization Following EUD principles, the user must be able to select and install only the specific packages needed to perform his/her particular work and not all the functionalities of the CGIS, assuming access priveledges Extensibility The system must be scalable according to the new needs of the organization, allowing the total re-use of the existing system • • Software distribution Organizations operate in a decentralized fashion, and conduct business in many geographical regions, therefore they require distributed computer support The software must be downloaded and installed across a network, avoiding repetitive, manual local installations Maintenance A centralized architecture helps in the administration of the system, because it allows updates of each independent piece (package) with a minimal cost General Structure Traditionally, the GIS architecture follows a clientserver schema, where the data processing takes place on the server side and the results are sent to the clients for the its representation At the server side, the system loses flexibility and introduces a performance bottleneck at executing time On the other hand, at the client side the system overloads communication between the server and the clients due to redundant functionality sent to the different clients Taking into consideration these aspects, the schema that has been adopted corresponds to a three-tier software architecture (see Figure 1) as a result of adding to a simple server-client schema a new tier located between the client and server in charge of user authentication If we take into consideration the possible geographic information databases of the system, the architecture (see Figure 1) can be naturally extended to a N-tier software architecture The proposed architecture exploits the main benefits of the web as transfer protocol (ubiquity, portability, reliability and trust) to deliver the different pieces that will conform to the GIS application The client layer is responsible for the interaction with the user and for the generation of the queries sent to the middleware with the user profile validation and authentication services These requirements, in practical terms, are achieved with a web-based system architecture where the client is a standard web browser and the A Package-Based Architecture for Customized GIS middleware is implemented as a web server The server layer, as repository, contains the packages that will be sent to the client after the processing of the middle tier messages The interchange of messages between the different layers is implemented as XML files (Aloisio, 1999) The process to get the final GIS application at the client side is as follows: Connection to the middleware layer through the client browser, the first time the user composes the GIS application and each time that the GIS application configuration is updated Validation and authentication with user name and password According to the user profile and package visibility privileges, the middleware displays a list of the possible packages (read here functionalities) that can be added to the final GIS application Selection of packages (functionalities) that the user requests to install XML configuration After receiving the result of the selection, the middleware dynamically creates a XML file that contains the user profile and packages configuration information This configuration file is sent to the server Processing at server side The server processes the XML configuration file and sends the selected packages to the client These packages are automatically connected to the client kernel thereby composing the updated GIS application Figure Architecture overview C L IE N T/BR O W SE R MIDDLEWARE V alidation S elected P ackages U pdate S election DATABASE xml SERVER X M L Interpreter R E P O S IT O R Y P ackage P ackage N K ernel 315 A Package-Based Architecture for Customized GIS Application C omposition After downloading the requested packages, the kernel builds and launches the application automatically Figure shows the general structure of the packages composition The CGIS has been designed in such a way that packages fit to the general structure of the kernel All the parts of the kernel to be accessed from external packages must be defined according to an open and well defined specification In the literature we find that these parts have been called “hot spots” or “point of extension” (Anderson and Moreno-Sanchez, 2003) After receiving the requested packages, the kernel examines them and extracts the information contained in a valid XML configuration file This configuration file must be defined according to the Document Type Definition (DTD) of the kernel and contains information about the points of extension to be extended For example, if for a particular GIS application (an instantiation of the CGIS) a particular extension of the GIS application menu is required, the XML configuration file must contain a label for the package to be included in the menu and for the associated actions Besides the hot spots, the kernel of the application exposes an interface that allows the packages to the access internal objects For access to the internal kernel objects, the packages must use this public interface of the kernel furthur fe atures Once the interfaces for the interaction of the pieces (kernel and other packages) and the hot spots of the CGIS are defined, developers are able to build up new packages with additional functionality and to simply include them in the CGIS for possible use by any client The remainder of the CGIS does not have to be modified, because of the structure of the CGIS that allows by design the direct inclusion or replacement of new packages The task of uploading new packages to the CGIS repository corresponds to the administrator of the system The users (CGIS clients) connected to the middleware tier, are able to add to the GIS client application new packages (functionalities) if they are visible according to the user profile The user needs to connect to the middleware only the first time that the application is built and downloaded or when an updating of any installed packages is need After the first time the GIS application has been downloaded and installed at the client side, the GIS application remains Figure Package composition GIS-APPLICATION Package xml Class Package Classes KERNEL xml Interface Extension xml Class Package N DTD xml 316 Class A Package-Based Architecture for Customized GIS in the local computer However, the user always may uninstall existing packages or the whole GIS application and download it again The administrator of the CGIS or any user with administrator privilege through the middleware tier is able to list the available packages, to delete any of them or to add new ones The administrator of the CGIS grants user privileges C onc lus ion In this paper we examine some of the limitations of GIS applications involved in public sector corporate environments Specifically, we concentrated on some crucial issues of integrating component-based software development and three-tier architectures for geographic information systems These ideas are the result of previous investigation into the uses of GIS software in the public administration and the possibilities of open source in this field We have attempted to find the appropriate design for corporate environments in an effort to minimize maintenance costs, while at the same time promoting the interoperability and flexibility of the resulting software framework In this article, we proposed an architecture, named CGIS, that allows the optimum distribution and installation of the GIS application, where each user can customize his/her application interactively The software architecture has been validated through the implementation of a testing prototype This development has been a key aspect in order to improve and demonstrate the design features The architecture is universal, not strictly related to any protocol, programming language or platform, though some characteristics of the selected implementation language, as for example platform independence, makes the system even more universal In particular, in the validation implementation Java WebStart was utilized with success Finally, the architecture creates a simple yet effective framework for the development of GIS applications With the inclusion of independent packages in a central server, different needs of the corporative environment can be supported As future work, we propose the implementation of new packages to extend functionalities of the current prototype It is important to make an effort to incorporate more open source libraries such as Geotools and Terralib that allow the creation of new packages with a minimum effort On the other hand, the system can be extended in the middleware layer We propose to add functionality for monitoring and controlling of downloads of the different users in order to produce useful statistics for administration purposes R eferences Aloisio, G., Millilo, G., & Williams, R.D (1999) An XML architecture for high performance webbased analysis of remote-sensing archives Future Generation Computer Systems, vol 16, 91-100 Anderson, G., & Moreno-Sanchez, R (2003) Building Web-Based Spatial Information Solutions around Open Specifications and Open Source Software Transactions in GIS, vol 7, 447 Anitto, R N., & Patterson, B L (1994) A new Paradigm for GIS data Communications URISA Journal, 64-67 Brown, A W (2000) Component-Based Development Prentice Hall PTR Camara, G., et al (2000) Terralib: Technology in Support of GIS Innovation II Workshop Brasileiro de Geoinformática, Geoinfo2000 Sao Paulo Fontoura M., Pree W., & Rumpe B (2001) UML Profile for Framework Architectures AddisonWesley/ACM Press Gosling, J., & McGilton, H (1996) White Paper: The Java Language Environment Java Articles: http://java.sun.com 317 A Package-Based Architecture for Customized GIS Guo J (2003) An Approach for Modeling and Designing Software Architecture 10th IEEE International Conference and Workshop on the Engineering of Computer-Based Systems (ECBS’03) Alabama Hartman R (1997) Focus on GIS Component Software OnWordPress Isnard E., Perez, E., & Galatescu, A (2004) MECASP – An Environment for Software Maintenance and Adaptation ERCIM News, No.58, 45-46 Longley, P.A., Goodchild, M.F., Maguire, D.J., & Rhind, D (2001) Geographic information systems and science Wiley and Sons Monson-Haefel, R (1999) Enterprise JavaBeans O’Reilly Press Morch, A.(1997) Three Levels of End-User Tailoring: Customization, Integration, and Extension M Kyng & L Mathiassen (Eds.), Computers and Design in Context The MIT Press, Cambridge, MA, 51-76 Morch A., Stevens G., Won M., et al (2004) Component-based technologies for end-user development Communications of the ACM, 47 (9), 59-62 Open Geospatial Consortium Inc (OGC) Web Map Service 1.3 (2004) www.opengeospatial org Pissinou, N., Makki, K., Park, E.K (1993) Towards the Design and Development of a New Architecture of Geographic Information Systems, ISBN:0-89791-626-3, 565-573, Washington Pree, W (1995) Design Patterns for ObjectOriented Software Development Wokingham: Addison-Wesley/ACM Press McKinley P., Masoud S., Kasten E., & Cheng B (2004) Composing Adaptive Software, Computer IEEE Computer Society, 37(7), 56-64 318 Rogerson D (1997) Inside COM: Microsoft’s Component Object Model Microsoft Press Schmidt, R (2001) Java Networking Launching Protocol & API Specification Java Articles http://java.sun.com key T er ms Application Programming Interface (API): The interface to a library of language-specific subroutines, for instance a graphics library that implement higher level graphics functions Binding: Language-dependent code that allows a software library to be called from that computer language CGIS: Corporate GIS A Corporate Geographic Information System is a GIS defined to be used as a corporate resource by the members of an enterprise or institution Client-Server Architecture: The term client/server was first used in the 1980s in reference to personal computers (PCs) on a network The actual client/server model started gaining acceptance in the late 1980s The client/server software architecture is a versatile, message-based and modular infrastructure that is intended to improve usability, flexibility, interoperability, and scalability as compared to centralized, mainframe, time sharing computing A client is defined as a requester of services and a server is defined as the provider of services A single machine can be both a client and a server depending on the software configuration Commercial Off-the-Shelf (COTS): A general term for software products that are made and available for sale or lease Component: In object-oriented programming and distributed object technology, a component is a reusable program building block that can be A Package-Based Architecture for Customized GIS combined with other components in the same or other computers in a distributed network to form an application Graphical User Interface (GUI):The graphical user interface, or GUI, provides the user with a method of interacting with the computer and its special applications, usually via a mouse or another selection device The GUI usually includes such things as windows, an intuitive method of manipulating directories and files, and icons Middleware: Layer(s) of software between client and server processes that deliver the extra functionality behind a common set of APIs that client and server processes can invoke XML: XML (Extensible Markup Language) is a flexible way to create common information formats and share both the format and the data on the World Wide Web, intranets, and elsewhere 319 320 Chapter XL Virtual Environments for Geospatial Applications Magesh Chandramouli Purdue University, USA Bo Huang Chinese University of Hong Kong, China Abstr act This article explores the application of virtual environments to 3D geospatial visualization and exploration VR worlds provide powerful functionalities for model generation and animation and are indeed a valuable tool for geospatial visualization Subsequently, related issues such as the constraints in progressive terrain rendering, geographic data modeling, photo-realism in virtual worlds, and the system performance with relatively larger files are discussed Nevertheless, to accomplish the desired results and to attain a higher level of functionality, a good level of experience in VR programming and the jurisprudence to choose the appropriate tool are necessary Although a standalone VR application is not capable of a higher level of interaction, using the SCRIPT nodes and the External Authoring Interface additional functionalities can be integrated Intended for use over the internet with a VR browser, such virtual environments serve not only as a visualization tool, but also a powerful medium for geospatial data exploration Introduct ion This chapter explores the application of virtual environments to 3D geospatial visualization, animation, and interaction The authors describe the design and implementation of some 3D models, which offer a good level of user-interaction and animation This chapter discusses related issues such as the constraints in progressive terrain rendering, geographic data modeling, photo-realism in virtual worlds, and the system performance with relatively larger files VR worlds provide Copyright © 2009, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited Virtual Environments for Geospatial Applications powerful functionalities for model generation and animation and are indeed a valuable tool for geospatial visualization Nevertheless, to accomplish the desired results and to attain a higher level of functionality, a good level of experience in VR programming practices is mandatory Even though a standalone VR application is not capable of a higher level of interaction, using the SCRIPT nodes, JavaScript can be embedded in the program to provide additional functionalities G eo- Vi rtu al E nv iron ments: E vo lut ion over the ye ars Since the 1960s and 70s, the past several decades have witnessed the ‘information revolution’, particularly in the domain of spatial information technology, propelled by the advancements in data acquisition techniques The evolution of diverse digital processing and image generation techniques over the decades along with the parallel developments in Geographical Information Systems GIS and remote sensing have resulted in colossal volumes of digital spatial data In order to make the utmost use of this collected data, they must be presented in the form of comprehensible information Geospatial data is increasingly being used for addressing issues involving environmental and urban planning, design, and decision-making within a wide range of disciplines ranging from urban landscape management to various other applications As geospatial data complexity increases, besides the standard rasters, Triangulated Irregular Networks (TINs) and Digital Elevation Models (DEMs), which are used for data exploration, additional tools such as photo-realistic models are needed to provide advanced visualization and query functionalities Three-dimensional visualization is a proven technique for exploring geospatial data (Bonham-Carter, 1994) In the work on urban modeling, Shiode (2001) explains the development of 3D models and their role within the domain of spatial information database and remote sensing technology The origins of concept of spatial immersion can be dated back to 1965 when Ivan Sutherland (1965) made known the ideas of immersion in virtual space in his influential work, “The Ultimate Display” Such immersive virtual environments can serve as handy tools for scientists and researchers that handle enormous data volumes By and large, visualization enables large quantities of information to be presented in a form that is comprehensible to a wide range of users (Colin Ware, 2000) 3D Geospatial Data Visualization: Tools and Techniques Geospatial analysis and research require that the data be in the 3D form Geospatial data is inherently three dimensional in nature since every spatial element has its own position or location in space (latitude, longitude, and altitude) A gamut of applications involving geospatial analysis such as environmental process simulation, infrastructure applications, landscape design, geological applications, etc necessitates three-dimensional exploration and visualization Traditionally, operations such as town or country planning relied heavily on drawings and these were eventually supplemented with Computer Aided Design (CAD) drawings However, one major handicap with these forms of data is that they try to symbolize 3D entities in 2D format Albeit these may offer a bird’s eye view of the place being studied, such representations depicting 3D data using two dimensions are incomplete and cannot replace a 3D view For instance, landscape and urban modeling architecture applications of today are far more complex and advanced tools are inevitable to provide the required level of sophistication Several techniques have been tried and implemented for visualizing 3D geospatial data This paper delineates some of the notable tools and 321 Virtual Environments for Geospatial Applications techniques that are employed in 3D geospatial data visualization and briefly elaborates the basic principles underlying the generation of static and dynamic virtual environments A plethora of commercial software is available for a wide range of purposes such as terrain or building generation, photogrammetric measurements, fly-through simulations, etc Typically, commercial software are designed for specific application requirements with the objective of saving time and costs Even though such software have been reasonably successful in accomplishing desired tasks, they are not capable of being extended to applications outside their intended domain and therefore, are inherently limited In order to overcome such limitations and to attain greater flexibility and efficiency, some researchers prefer the 3D virtual environments using a variety of powerful programming languages Even though, initially, building the 3D worlds from scratch might be time-consuming process, with time and experience, using programming languages to model becomes easier Moreover, the tremendous functionalities and flexibility offered by different programming languages make the final 3D virtual environments worth the effort Some popular languages for writing code to generate advanced 3D environments include VRML, GeoVRML, X3D and OpenGL VRML is a specification designed to create interactive 3D worlds that can be used on the World Wide Web GeoVRML can be considered a derivative of VRML because it is used to create geo-specific applications Of late, research involving the development of 3D geospatial applications has been gaining increasing significance, and the inherent complexity in the efforts to visualize geographical phenomena has necessitated the amalgamation of the aforementioned tools with conventional programming languages owing to the powerful functionalities offered by the latter 322 APP LIC AT IONS OF GEO -V IRTU AL ENV IRON MENTS Visualization facilitates not only presenting information, but also enables seeing and understanding hidden information among datasets As mentioned in the previous section, huge volumes of data are available today and it is practically impossible to manually sift through these huge amounts of data Using visualization techniques, data can be presented in a much more organized manner that facilitates understanding the information that may not otherwise be apparent By proper use of visualization tools, the same area can be viewed at different scales, i.e., a small area in detail or a bird’s eye view of a larger area In order to see the overall landscape of a whole country we need to view the entire country at a glance However, the advantage of modern visualization is that such visualizations are not mere depictions of scenes, but also interactive environments capable of animating the scenes, and simulating phenomena Another kind of information that needs to be discussed in this context is associated information In order to understand these links among the various components of a system, tools that can reveal the various concurrent processes among the various sub-systems are vital Solutions to many complex problems can be found by understanding the relationships among the system components Urban planning authorities and town planners face several problems such as managing water shortages, transportation problems, urban housing and land use problems, natural and man-made disasters, etc Several of these problems are mutually dependant and trying to solve them in isolation will never lead to a permanent or long-lasting solution One of the foremost steps in solving these problems is to get a bird’s eye view of the problem scenario as a whole, while simultaneously concentrating on the minutiae (Figure 1) This kind of visualization is of immense value to town Virtual Environments for Geospatial Applications and country planners and urban infrastructure management in understanding the link among the various components Also, the influences on the ambient environment as a result of the aforementioned project can be studied by means of the virtual settings The visual impact of new buildings and surroundings on each other can be vividly seen on the screen Two main classes of models are discussed here, namely static and dynamic models The static 3D models are used for planning and design purposes, while the dynamic models are used for simulation and training purposes Such immersive models are of immense value in the planning and decision-making processes involving terrain and building databases Such models serve as valuable tools in solving the previously mentioned urban infrastructure problems The emphasis here is not only on the utilization of virtual worlds for visualization but also for simulation and animation Three-dimensional virtual environments are being increasingly used for disaster mitigation and managing events such as debris flow, volcanic eruption, seismic activities, etc Static Geo-Virtual Environments Static virtual environments are those that are composed of objects that lack animation capabilities Simply stated, the depiction of a 3D model of a building is a static representation, while 3D illustrations of phenomena such as debris flow or volcanic activity involves dynamic representation Researchers use different approaches to model or create the 3D virtual worlds and depict the constituents of those worlds One very efficient method of describing real-world scenarios is the use of a hierarchical scene tree structure Especially, several 3D modeling languages (X3D, VRML, and GeoVRML) model real-world objects as shapes with geometry and appearance All features such as buildings, roads, trees, and rivers can be designed and modeled as shapes which can be grouped together and transformed (translated or rotated) Objects in the real-world have positional attributes and these are represented in the form of the x, y, and z coordinate points within the virtual world The topological relationships among the constituent elements of a scene can be represented and the virtual representations can Figure Geo-virtual environments for visualizing interlinked components of urban infrastructure Clockwise from top-left a A Sample urban landscape, b Land parcel, c Road network, d parcel with proposed building layout 323 Virtual Environments for Geospatial Applications Table A summary of applications of Geo-virtual environments • • • • • • • Geospatial visualization and animation Urban planning and Infrastructure applications Environmental process simulations Resource management and conservation Hosting cyber cities online Imparting training and demonstration purposes Simulating applications such as mining, seismic processes, etc be built to scale The virtual world scene is built within a virtual coordinate system, in which the x and y axes are along the length and breadth of the computer monitor and the z axes extends in a direction perpendicular to the monitor Hence, theoretically, an object that is at a distance of 10 units along positive z-axis is in front of an object at units along positive z-axis Also, the notion of the parent-child relationship (Figure 2) implies that smaller objects can be grouped to form larger ones or objects higher in the hierarchy and these are, in turn, grouped to form objects still higher in the hierarchy Typically, various modeling approaches use the notion of point, line, and polygon, as in GIS, to build virtual worlds All constituent elements of a 3D scene can be built using fundamental entities such as point, line, and polygon or faces Simple objects such as cuboids might be composed of just faces, while complex objects might necessitate a greater number of faces Photo-realistic environments can be built by the judicious use of textures and by scaling them to accurately match the faces A vast number of environmental and landscape applications generated using Virtual Reality (VR) or VRML are available on the Web Several researchers have generated virtual environments for geospatial applications (e.g., Huang et al., 1999; Chandramouli et al., 2004), resource management (e.g., ref: SGILICGF, UW), 3D urban applications (e.g., Shiode, 2001), etc For some applications a mere representative environment depicting the relative positioning of various elements would suffice, but Figure a) Scene tree structure; b) Parent-child relationship 324 (a) (b) Virtual Environments for Geospatial Applications Figure a) A point in 3D space; b) Vertices of a polygon; c) Polygon with sides (a) (b) (c) Figure a) Community planning with less photo-realism; b) Sample urban landscape with higher degree of photorealism (a) others might necessitate photo-realistic rendering of the 3D scene Figure 4a (left) shows a simple 3D environment showing a general layout of houses within a community without much photo-realism On the other hand, Figure 4b (right) shows an advanced infrastructure application wherein the finished product, or final environment, is required for viewing by planners in advance and hence the virtual world is depicted with a higher degree of photo-realism One advantage of the hierarchical mode of representation, in which the scene elements are modeled as individual objects that are grouped using parent-child relationships, is that objects can be built once and used any number of times either in the same virtual scene or in other virtual (b) environments This is known as the concept of ‘reusable software objects’ For instance, a lamp object or a tree object that has been created for a particular project can be reused in another application Just like using a math function from a C library, objects modeled within virtual environments (Figure 5) as part of one project can be referenced and included as part of another application, thereby saving considerable programming time and effort Dynamic Virtual Environments As mentioned in the previous section, dynamic virtual representations refer to those 3D worlds in which the objects are incorporated with animation 325 Virtual Environments for Geospatial Applications Figure Reusable software objects – can be generated once and used multiple times a Trees – Vegetation b Lamp-posts capabilities Quite frequently, research involving the study of real-world geospatial processes and phenomena, for instance seismic activity or hydrological processes, necessitates that the virtual environments possess dynamic animation capabilities The inherent nature of such activities makes on site evaluation of such phenomena an extremely hazardous task Moreover, such disastrous events might be triggered by a variety of factors, both known and unknown, and hence, predicting their occurrence accurately still remains a challenging task Hence, 3D geospatial environments offer an efficient means of modeling such phenomena and studying them at the comfort of an office desktop Virtual reality serves as an extremely potent and flexible tool for applications involving simulation and animation since it has functionalities capable c Inventory elements – Bus shelter of being extended to achieve desired results Modeling languages such as GeoVRML, VRML, and X3D provide additional functionalities known as Scripts that can be programmed and executed to create simple animations However, these 3D modeling languages lack advanced programming functions to achieve curvilinear motion or more sophisticated forms of animation In order to incorporate dynamic behavior in the virtual world objects and replicate complex animation patterns, an existing programming language with advanced functionalities, for instance Java or JavaScript, can be used in conjunction with the 3D modeling language Typically, the objects in a parent-child relationship within a virtual scene are grouped into structures called nodes In order to achieve animation, these nodes must be made to Figure Flow of events within a virtual world wherein objects are grouped I the form of nodes 326 Virtual Environments for Geospatial Applications sense user actions or events (Figure ) In case of simple actions such as the movement of an object upon impact, there is a ‘trigger’ or a stimulation, upon which something acts In programming, the ‘triggering action’ is referred to as an event Upon the occurrence of a particular action, an object or group of objects (node) behaves accordingly Events may not always be explicit or need not only be ‘physical movement’ In programming context, even the reaching of an instant of time, say 11:59 pm, is considered an event Hence, an object or a group of objects (Parent node) can be programmed to ‘sense’ the particular instant of time and behave in a particular fashion upon reaching that moment The word ‘sense’ has been highlighted as it is inevitable that an object or a group of object recognize a change of condition (state) Typically, there are three kinds of sensors that are used in order to sense time changes, cursor movement over the screen or objects, or the field of view from a particular position within the virtual world These are respectively called time sensors, touch sensors, and visibility sensors in the context of virtual worlds (Figure 7) Upon reaching a particular instant of time, or when the mouse cursor is pointed on a particular object, or when the viewer is within the virtual world is at a specific position, the objects in the scene can be programmed to behave in a desired fashion This behavior or response of objects might be a translation along the x, y, or z axis or a rotatory motion, or a combination of both Based on the above principles of animation, dynamic geo-virtual environments can be generated to simulate various processes or geospatial phenomena Environmental processes and natural disasters can be studied in detail by generating dynamic virtual worlds By programming the properties and behavior of the constituent objects, the 3D virtual environments can be used to study various occurrences which are not easy to be observed in real time, e.g., Figure describes flow events, seismic activities and the responses of structures to such events Figure Diagram illustrating the sensing of actions of events by the objects and the corresponding movement based on the flow of events (From Chandramouli et al., 2004, 2006) 327 ... Location Services In M Khosrow-Pour (Ed.), Encyclopedia of Information Science and Technology, 4, 1 973 -1 977 Pennsylvania: Idea Group Reference Harrington, A (2000a) GIS and GPS: Technologies that... Geographic Information Systems and Science New Jersey: John Wiley & Sons, Inc (pp 122-123, 172 - 173 ) Ramadan, K (1998) The Use of GPS for GIS Applications Proceedings in the Geographic Information. .. system is able to offer location information with an accuracy of 70 meters There were 17 satellites in operation by December 2005 offering limited usage With the participation of the Indian government,