WEB BASED GEOGRAPHICAL INFORMATION SOURCE
A Dissertation Submitted to the Central University of Himachal Pradesh for the award of Degree of
MASTER OF LIBRARY AND INFORMATION SCIENCE
(School of Mathematics, Computer and Information Science ) By
(Regn NO: CUHP11MLIB08) Supervisor
Dr. I V Malhan
Professor Department of Library and Information Science
CENTRAL UNIVERSITY OF HIMACHAL PRADESH DHARAMSHALA
I, Shivani Shama, Mlib.Sc.-IV CUHP11MLIB08, declare that dissertation ‘WebBased Geographical Information Source’ is an authentic record of study work carried by me and that no part of it has been presented before any one for any other degree, diploma, or titles. The study work carried out under the supervision of Prof.I.V.Malhan Prof and Head, Department of Library and Information Science, Central University of Himachal Pradesh ,Camp Office , Dharamshala,Kangra, Himachal Pradesh and no part of this work either in part or in full to this or any other university has not been submitted earlier for the award of any other degree or diploma.
This is to certify that Miss. Shivani Shama is a bonafide student
TITLE: Web Based Geographic Information science
Prof. I .V. Malhan
Central University of Himachal Pradesh
DEGREE OF BE AWARDED: Master of Library and Information Science
UNIVERSITY ROLL NO:
Chapter :1 INTRODUCTION
Introduction of Web –Based GIS:
The advent of the Internet has seen a number of Geographic Information Systems utilizing its potential to disseminate Geographic Information. Internet features such as platform independence, accessibility to large groups of population worldwide and technical features such as progressive transmission of raster images (Berta lotto, 1999) and development of software packages with GIS functionality has helped its growth in the GIS industry. Initial GI Systems emerged as „display only‟ static web pages and have evolved to provide basic spatial operations, often using dynamic pages (Geodata resources, 2000). While stand alone GIS have become specialized and highly complex vendor specific software packages, Web based GIS comprises of relatively small pieces of software or components, which perform particular GIS operations, namely Cartographic Visualisation (Rinner, 1998).
There are a number of Web Based GIS systems on the Internet, which could be generalized into a number of categories. Rinner (1998) specifies five different categories in the form of Internet Mapping Applications, based on their functionality, while Plewe (1997) describes eight types of Distributed Geographic Information (DGI) Systems. In addition to these we could categories Web Based GIS based on its source. Two types of sources could be identified: Single source GIS (data and operations from single website/server) and multiple
heterogeneous Sources (data or operations from multiple sites/servers). While the latter would be the ideal distributed GIS, either on the Internet or an Intranet, it presents numerous issues related to heterogeneity preventing it from being fully realised on the web yet (p Plewe et. al). Single source GIS will be therefore the subject of discussion in this paper. Amongst the single source systems, static and dynamic pages could be further sub-classified. Static pages, limited in its ability to perform spatial operations, form a fair portion of Web Based GIS. Dynamic pages on the other hand, while providing more realistic GIS functions, are the most widely used. Various solutions such as procedural language based applications (e.g. Java), Internet standards based solutions (e.g. Extensive Markup Language (XML), Geographic Markup Language (GML), Scalable Vector Graphics (SVG)) and other vendor specific graphics packages such as Macromedia Flash has been used to create dynamic Web Based GIS. However real GIS functionality has been only provided by major GIS vendors such as ArcIMS from ESRI (ESRI, 2000) and MapExtreme from MapInfo Corporation (MapInfo , 2001) which are software specific. This paper is an attempt to provide an overview of the current status of Web Based GIS by looking into the different types of systems that have been implemented, its techniques and the trends in the industry. The next two sections will try and categorise the current Web Based GIS in use, while section 4.0 will look into some of the techniques employed by these systems. We also discuss some of the advantages and disadvantages and the emerging technologies/techniques for deploying Web Based GIS.
•GIS is a powerful set of tools for collecting, storing, retrieving,
managing, analyzing and displaying spatial data.
•Users can combine data and information accessed over the Intranet or Internet with the local data for display, query and analysis.
•Internet allows all levels of society to access geospatial information and provide same media for processing geo-related information with no location restrictions.
•Web GIS is a mechanism to deliver maps and GIS services on the internet.
•Web GIS is a viable tool for building various geospatial Web
•Traditionally, in Web GIS all the geographic data was stored on a single server i.e. it uses a centralized paradigm approach.
•Web GIS is a cost effective, easy and efficient way to access and disseminate the geographic information, spatial analysis tools and geospatial web services.
WEB GIS CONCEPT
GIS is increase more then three-tier. These tier and components can be distributed to a variety of location over the internet . Web GIS and desktop GIS increasing intertwined. WEB GIS relies on desktop GIS author resource. Desktop GIS on the other hand has expanded its functionality to make use of the resources on the web.
where the required run-time environment is installed. It is worth mentioning that web GIS for mobile client is far from being cross platform because of the diversity in mobile operating system and the current incompatibility of mobile Web browser. Low cost as averaged by the number of user: In the spirit of the internet the vast majority of internet content are free of charges end user, and this is true of web GIS. Organization need to provide GIS capabilities to many user can also their web GIS cost low. Instead of buying and setting up desktop GIS for every user an organization can set up just one web GIS, and single system this can be shared by many user-from home at work ,or in the field. The reduce costs in purchange and maintenance help to provide a high return on investment. Easy to use for end user: Desktop GIS is intended for professional user with year of training and experience GIS. web GIS is intended for a broad audience, including public you may now nothing about GIS. The expect web GIS to be as easy as using a regular Web page. In GIS the web 2.0 era, their expectations are even higher –“if I don’t now how to use your site, it’s your fault .” Web GIS commonly designed for simplicity, intuitions, and convenience, makings it typically much easier for end user than desktop GIS. Unified update : For desktop GIS, to be update to a new version, the update needs to be installed on every computer. For Web GIS, one update work for all client, making update lot easier. As long as the program and data are updated on the server most
Web GIS client will get automatic update. This mean easy maintain for Web GIS and greatly improved timeline for GIS making Web GIS a good fit for delivering real-time information. Diverse applications : Unlike desktop GIS, which is limited to a certain number of GIS professional, Web GIS can be used by everyone in an enterprises as well as by the public at large. This broad audience has diverse demand, which result in Web GIS being used in a variety of applications, both formal and informal. Neogeography (i.e.” new geography” ) is a concept that is gaining popularity as none expert user employee geographic techniques and tools for personal and community purpose. While not strictly Web-based, neogeography typically refer to such simple and informal applications as mapping celebrity home, tagging personal photos, locating friends, displaying WiFi hot spot, and making location of news events. TYPES OF WEB BASED GIS APPLICATIONS A number of various web based GIS systems currently exist on the Internet. Attempts have been made to classify them into homogenous groups either through functionalities or types of systems. Renner (1998) specifie five categories based on functionality and Pelew (1997) specifies eight categories as they fit to Distributed Geographic Information Systems. Renner‟s classification includes 1) Geodata Server: A “Geodata server” provides functions for searching geo referenced data files and downloads them to the local machine for further local processing. 2) Map Server: “Map Servers” provide online visualization of Geodata including simple map functions like zooming and panning.
3) Online retrieval systems: Online retrieval systems add thematic and simple retrieval functions to a map server while online GIS offer access to analysis functions and data of remote GIS via the Internet. 4) “Online GIS” 5) GIS Function Server: A “GIS function server” allows clients to use remote functions for local processing.
Web GIS Heterogeneous Sources Single Source Dynamic Pages Static Pages Display and Advanced Spatial Operations Display and basic Spatial Operations
2.1 Single Source Systems The Web based GIS sends requests to the Web Server and Web Server responds back with the request information after processing it. The Server Side may implement various architectures such as two-tier or three tier Client /Server architecture where it could have multiple data servers connected to it (Brinkhoff, 2000). The single web server however is the sole supplier of information. This is the most common and perhaps the only available form of web GIS in use today. These
systems behave logically like a conventional GIS's in that they are based on one underlying GIS. Single source systems can be further sub divided as static and dynamic pages. This identifies the behavior of the actual web page the web GIS uses as an interface. Static pages are used here as referring to pages that sends Pre defined requests to a web server where the data has already been prepared. A good example would be the use of GIF images to display maps based on user clicks (example: Canterbury, 1998). Dynamic pages on the other hand refers to web pages that sends requests to a web server that would generate the contents from the requested query on the fly (Brinkhoff, 2000). This is once again the most common form pages used in Web based GIS that offers any promise of GIS functionality. The main function of a web based GIS is visualisation of spatial data based on user queries (Peng, 1997). There are different methods used achieve this in each of these type of web pages. Dynamic pages can use capabilities of procedural languages, server side scripting languages, internet standards or vendor specific GIS and graphics software to achieve it while static pages just requires image maps or vector display plug ins. These sub classifications will be discussed in sections 4.0 and 5.0 respectively.
2.2 Systems based on Heterogeneous Sources These System represent the idea that a web based GIS could request data from multiple web servers and use them to perform spatial operations. For example, in a true web based GIS single site should be able to request different layers from different sites and use them to perform spatial operations. This goes back to the concept of Distributed Geographic Information Systems (DGIS). The Internet creates the perfect settings for a DGIS in terms of the network and platform independence. However there remain a lot of unresolved issues in the DGIS
area that its practical implementation at a large scale requires barriers to be crossed (Markov et. al. 1999). The main barrier remains as interoperability, which refers to the capability of autonomous systems to exchange data and to handle processing requests by means of a common understanding of data and requests (Gronmo, 2000). Organizations such as Open IS Consortium are working overcoming the interoperability barrier through definition of industry standards to implement spatial data in a GIS intended for distribution (OGC, 2001). The Simple Features Specifications and Internet Map Server are two such specifications released so far (OGC,2001). Further work on creating common metadata definitions for transfer between dissimilar systems is also expected to contribute to help interoperability (Plewe et. al., 1997). Due to these issues Web based heterogeneous GIS have failed to be successfully implemented so far at a large scale. However in the tradition of Internet to tap the vast resources of interconnected data, heterogeneous systems could be the ultimate GIS for the web. This classification while not comprehensive represents a simpler look at the types of Web GIS systems in use and in development. It is not intended to serve as a classification model for Web Based GIS systems but as an aid to understanding the current web GIS systems. We therefore will be basing further discussion on these systems based on the above classification and mainly on single source, web based GIS. 3. STATIC PAGES As mentioned above Web based GIS utilizing static web pages use predefined set of information that has already been published into a web page (Geodata resources, 2000). These pages with the required elements (mostly graphics and text) are displayed on request of the user who follows the links from the home page. These GIS often tend to have a large number of stored web pages depending on the functions provided and tends to grow proportionally to level of detail provided. The earliest Web GIS systems tended to follow this method since it was simple and efficient for most of the for the more common GIS operations, namely
cartographic visualizations (Geodata resources, 2000). These pages are hence used mainly for display only purposes. Spatial data can be stored in the form of either raster or more recently vector data. Raster data are the more commonly used type for such sites through the use of compressed image formats such as GIF (Graphics Interchange Format) or JPEG (Joint Photographers Expert Group). Raster images can be used to display images through text hyperlinks or for a more visual linkage through Image maps. Image map is a method used to embed hyperlinks into portion of image creating a more visual interaction (Brinkhoff, 2000). Hence this method has been widely used to provide basic operations such as "zoom" and "Pan" in static web based GIS. There are some disadvantages in using raster images that load from a static web page. Firstly the image size needs to be small for it to be displayed quickly and secondly if the image size is too small the data quality is reduced especially in maps. More recently graphics software packages have emerged to provide vector data on a web page promising to solve the limitations posed by raster data. A product that has grown rapidly in this area is Macromedia Flash, which allows vector data to be viewed using a plugin. This allows the graphic quality to be vastly improved and reduce the size required to display a given area (FreshMaps, 2001). Static pages can be used to answer queries submitted by a user. However such queries cannot be adhoc and information relating to the query must be already published into a web page. Hence if adhoc querying is required, that GIS should be implemented using dynamic webpages. An example of web based GIS utilising static pages include, the Canterbury Tour Map (Canterbury, 1998), where it uses an underlying map (in GIF format) to provide links to images via an image map. More examples can be found in Kart web (Kart web, 2001). Hence static pages are used in a web based GIS if the system is relatively simple, display only and do not require adhoc querying. An added advantage is that such a GIS is relatively simple to create and hence a lot cheaper than more complex ones.
4.DYNAMIC PAGES Dynamic pages can be referred to as those web pages that can create content dynamically based on users requests. Queries can be generated on the fly and as required while the web server can process them and return the information promptly (Kartoweb, 2001). Web based GIS systems that require basic visualization and spatial operations to be performed often require such capabilities to both query and manipulate the visualization of data. Web based GIS that is based on dynamic pages comes close to doing what conventional GIS can do in terms of spatial data visualization. We have identified two groups of dynamic pages used in Web based GIS. The first group can visualize data and perform basic map visualization and minimal spatial operations such as "zoom"/"pan" functions and layer overlays. The second group bears the closest resemblance to conventional GIS through the facilitation of advanced spatial operations. The major GIS software vendors such as ESRI, MapInfo and Autodesk only provide such facilities. 4.1 Display and Basic Spatial Operations As mentioned above, this group of Web GIS systems is capable providing advanced visualizations and minimal spatial operations. These systems often tend to be adequate for a large portion of web based GIS's. It could be that the basic spatial operation such as layer overlay, visualization by layer and distance and location calculation are adequate for a simple web based GIS. One other feature of this group of systems are that they tend to be developed using procedural languages, or based on an Internet standard or a graphics software. 4.1.1 Procedural language based Procedural languages have played a major part in recent years to add more functionality to web pages (Peng,1997). Major procedural language vendors such as Sun and Delphi has provided capabilities for creating both server and client side applications to increase the potential of running small programs especially in a web browser (Java, 2001). Java has more importantly emerged as a popular choice because of its built in platform independence features. Java
applets have become a popular choice for some the web based GIS systems to create an interface to a GIS. Applets can be used to create a client program that can run on client machine allowing both advanced display features and programmed basic spatial operations such as map overlay, distance and area calculation and attribute display based on hyperlinks. JShape (JShape, 2001) is a software vendor that provides Applets for basic web based GIS. A good example of a Web based GIS designed using Java is the City of Sydney (2000) web page, which has incorporated a number of basic GIS operation. 4.1.2 Internet Standards Based Hyper Text Markup Language (HTML) has been the main language for publishing web pages. It is mostly a text and image display oriented language that lacks graphic capabilities and ability to store information for a given web session (Marshall, 2001). Additional languages have been developed in the form of standards to overcome the limitations in HTML. Such standards include eXtensive Markup Language (XML) and its sister languages, Vector Markup Language (VML) and Scalable Vector Graphics (SVG). XML is a means of encoding data in text allowing it to be embedded into browsers the same way as HTML tags (W3C, 2000). For web based GIS systems, XML encoding of geographic objects is available through the Geographic Markup Language (GML) developed by the OpenGIS consortium (OGC, 2001). GML can be used to define geographic objects and assign specific meanings and behaviour to them (Lake, 2001). Graphics display languages such as SVG can be used to represent the geographic object in a more efficient manner (W3C, 2001). Web GIS systems implementing these standards have successfully started to emerge. Examples of such implementations can be seen in DBx Geomatics (DBx Geomatics, 2001) and AxioMap (AxioMap, 2000) homepages.
4.1.3 Graphics packages
Apart from the procedural languages and Internet standards, graphics software packages have helped in providing high quality display for spatial data and the programming capability to allow basic GIS operations. Most notable of these graphic packages is the Macromedia Flash, which has started to dominate the provision of vector graphic on the Internet. Web based GIS systems have been developed in flash that provides high quality display and basic spatial operations such as individual layer display, layer overlays, location determination and distance calculations (Fresh Maps, 2001). Furthermore, it provides builtin visualization features such as zooming and panning to allow for easy navigation as we would in a conventional GIS. Example web based GIS systems developed using Flash can be viewed from Fresh Maps Gallery (Fresh Maps, 2001). 4.2 Display and advanced spatial operations. Most of the web based GIS developed using the above mentioned techniques cannot provide advanced spatial operations like querying of spatial data using spatial operators (such as „within‟ and „contains‟). Furthermore, they are unable to provide advanced functions that are provided in a conventional GIS. Most GIS software vendors that provide conventional GIS have created their own special versions or software packages for developing web based GIS. These software often have the advanced capabilities of their conventional GIS software borrowed and hence seems the most appropriate method to develop a web based GIS. In fact, they are the closest a web GIS can get today to a conventional GIS. Some of the leading web based GIS development software packages include ESRI's ArcView IMS, Map Object IMS and ARC IMS, MapInfo Corporation's MapXtreme, Autodesk's Map Guide, Intergraph‟s GeoMedia Web Map and USL's Caris Internet Server (Geodata resources, 2000). Most of these software packages provide a conceptually similar method to create a web based GIS. On the server side a Map Server exists with the capability to perform various advanced spatial operations. The client side most of the times consists of a viewer that can be used in a web
browser that will communicate with the map server and manipulate the visualization process (Marshall, 2000). This is in effect very much like working with a conventional GIS for the end user. It could be said that these vendor specific programs are starting to dominate the web based GIS arena. However if we look into the web based GIS that has been implemented using these packages, we find a pattern that it is once again (as with conventional GIS) the governmental organizations and larger companies that implement it. The reason could be simple: these packages are too expensive for it to be used by smaller organizations(WebGis.net, 2001). That in effect could be the reason why we see alternate methods being developed such as those discussed in the previous section. Further drawbacks to some vendor specific packages Like MapGuide are the size of the viewer that is required to be downloaded by the client. If user wants to simply see whether a map fits his/her needs and the web based GIS is implemented for example using MapGuide, the user has to wait before he/she can download the viewer, which is over 2 megabites (MapGuide, 2001), and then make the decision. In spite of these issues, these software packages could be the most efficient way to implement a useful web.
ADVANTAGES AND LIMITATIONS OF WEB BASED GIS ADVANTAGES
Web based GIS systems promise a number of advantages over the conventional GIS. It enjoys all the advantages of the Internet as a whole namely mass accessibility to geographic data. In conventional GIS, it is restricted to a location or specific locations it. Web GIS removes this barrier and makes them accessible to a larger audience, more importantly community wide or worldwide.
Accessibility is further enhanced with the platform independence and non-propriety software on the client side. The cost of implementing a web based GIS is much cheaper if we take into consideration the audience they convey the information (WebGIS.net, 2001). More importantly, for the client, the cost is almost none to access the information. Apart from being cheaper, web based GIS are much easier to learn than conventional systems as they are based mostly on Internet standards (Geodata Resources, 2000).
Although the functionality may be limited, it provides enough for most of everyday users of the system. Further more the client side software or plugin comprises of small component(s) of a conventional GIS making them easier to learn than the much more complex GIS packages. The main limitation of a web based GIS is once again related to the problems of data transfer on the Internet i.e. response time being slower (Brady, 1998). Web based GIS systems often tend to be larger systems especially if they use raster images for spatial data visualisation. A number of factors such the efficiency of client and server computer, speed of Internet connection, amount of network traffic at a given time and data efficiency could dictate the response time (Geodata Resources, 2000). Since most web based GIS systems are designed to query and analyse a given set of data the communication between the client
and server could be high hence increasing the chances of network delays affecting the client (Peng, 1997). High-speed connections in the form of ISDN connections are now available but costly. Hence a large portion of the average users would still be using a maximum of 56K modem connections to get their information from the web based GIS. Hence the only way to minimise this problem would be design the web based GIS keeping in mind the issues of network latency. Further limitation of web based GIS include its inability to manipulate raster images (Brinkhoff, 2000). Image maps can be used to add some form of visualizations capabilities but is limited only to navigation to other pages. The problem partly could be due the limitations in the speed of data transfer, which for raster images is often critical.
Chapter :2 Web Mapping: GIS Introduction Web mapping is the process of designing, implementing, generating and delivering maps on the World Wide Web and its product. While web mapping primarily deals with technological Issues, web cartography additionally studies theoretic aspects: the use of web maps, the evaluation and optimization of techniques and workflows, the usability of web maps, social aspects, and more. Web GIS is similar to web mapping but with an emphasis on analysis, processing of project specific geodata and exploratory aspects.Often the terms web GIS and web mapping are used synonymously, even if they don't mean exactly the same. In fact, the border between web maps and web GIS is blurry. Web maps are often a presentation media in web GIS and web maps are increasingly gaining analytical capabilities. A special case of web maps are mobile maps, displayed on mobile computing devices, such as mobile phones, smart phones, PDAs and GPS.If the maps on these devices are displayed by a mobile web browser or web ,user agent, they can be regarded as mobile web maps. If the mobile web maps also
display context and location sensitive information, such as points of interest, the term location based services is frequently used. "The use of the web as a dissemination medium for maps can be regarded as a major advancement in cartography and opens many new opportunities, such as realtime maps, cheaper dissemination, more frequent and cheaper updates of data and software, personalized map content, distributed data sources and sharing of geographic information. It also implicates many challenges due to technical restrictions (low display resolution and limited bandwidth , in particular with mobile computing devices, many of which are physically small, and use slow wireless internet connections), copyright and security issues, reliability issues and technical complexity. While the first web maps were primarily static, today's web maps can be fully interactive and integrate multiple media. This means that both web mapping and web cartography also have to deal with interactivity, usability and multimedia issues.
Development and Implementation
The advent of web mapping can be regarded as a major new trend in cartography. Previously, cartography was restricted to a few companies , institutes and mapping agencies , requiring expensive and complex hardware and software as well as skilled cartographers and geometrics engineers. With the rise of web mapping, a range of data and technology was born - from free data generated by openstreetmap to proprietary datasets owned by navteq, Google, waze, and others. A range of free software generate maps has also been generated, alongside proprietary tools like ArcGIS. As a result, the barrier to entry for creating maps
on the web has shifted from that of the paper atlas and other traditional cartography. Types of web mapping A first classification of web maps has been made by Kraak. He distinguished static and dynamic web maps and further distinguished interactive and view only web maps. However, today in the light of an increased number of different web map types, this classification needs some revision. Today, there are additional possibilities regarding distributed data sources, collaborative maps, personalized maps, etc.
Analytic web maps These web maps offer GIS analysis, either with geodata provided, or with geodata uploaded by the map user. As already mentioned, the borderline between analytic web maps and web GIS is blurry. Often, parts of the analysis are carried out by a serverside GIS and the client displays the result of the analysis. As web clients gain more and more capabilities, this task sharing may gradually shift. Animated web maps Animated Maps show changes in the map over time by animating one of the graphical or temporal variables. Various data and multimedia formats and technologies allow the display of animated web maps: SVG. Adobe Flash, Java, QuickTime, etc., also with varying degrees of interaction. Examples for animated web maps are weather maps, maps displaying dynamic natural or
other phenomena (such as water currents, wind patterns, traffic flow, trade flow, communication patterns, social studies projects, and for college life, etc.).. Collaborative web maps Collaborative maps are still new, immature and complex to implement, but show a lot of potential. The method parallels the Wikipedia project where various people collaborate to create and improve maps on the web. Technically, an application allowing simultaneous editing across the web would have to ensure that geometric features being edited by one person are locked so they can't be edited by other persons at the same time. Also, a minimal quality check would have to be made, before data goes public. Some collaborative map projects: Map creator
Google Map Maker OpenStreetMaps WikiMapia Meta map: - survey of Wikimedia map proposals on Wikipedia:Meta
Dynamically created web maps These maps are created on demand each time the user reloads the webpages, often from dynamic data sources, such as databases. The webserver generates the map using a web map server or self written software. Online atlases
Atlas projects often went through a renaissance when they made a transition to a web based project. In the past, atlas projects often suffered from expensive map production, small circulation and limited audience. Updates were expensive to produce and took a long time until they hit the public. Many atlas projects, after moving to the web, can now reach a wider audience, produce cheaper, provide a larger number of maps and map types and integrate with and benefit from other web resources. Some atlases even ceased their printed editions after going online, sometimes offering printing on demand features from the online edition. Some atlases (primarily from North America) also offer raw data downloads of the underlying geospatial data sources. Realtime web maps Real time maps show the situation of a phenomenon in close to realtime (only a few seconds or minutes delay). Data is collected by sensors and the maps are generated or updated at regular intervals or immediately on demand. Examples are weather maps, traffic maps or vehicle monitoring systems.
Static web maps Static web pages are view only with no animation and interactivity . They are only created once, often manually and infrequently updated. Typical graphics formats for static web maps are PNG, JPEG , GIF, or TIFF (e.g.drg) for raster files, SVG, PDF or SWF for vector files. Often, these maps are scanned paper maps and had not been designed as screen maps. Paper maps have a much higher resolution and information density than typical computer display of the same physical size, and might be
unreadable when displayed on screens at the wrong resolution.
Advantages of web mapping Web maps can easily deliver up to date information. If maps are generated automatically from, databases, they can display information in almost realtime. They don't need to be printed, mastered and distributed. A map displaying election results, as soon as the election results become available. A map displaying the traffic situation near realtime by using traffic data collected by sensor networks. A map showing the current locations of mass transit vehicles such as buses or trains, allowing patrons to minimize their waiting time at stops or stations, or be aware of delays in service. Weather maps, such as NEXRAD.
Software and hardware infrastructure for web maps is cheap. Web server hardware is cheaply available and many open source tools exist for producing web maps.
Product updates can easily be distributed. Because web maps distribute both logic and data with each request or loading, product updates can happen every time the web user reloads the application. In traditional cartography, when dealing with printed maps or interactive maps distributed on offline media (CD, DVD, etc.), a map update caused serious efforts, triggering a reprint or premastering as well as a redistribution of the media. With web maps, data and product updates are easier, cheaper, and faster, and can occur more often.
They work across browser and operating system. If web maps are implemented based on open standards, the underlying operating system and browser do not matter.
Web maps can combine distributed data sources. Using open standards and documented APIs one can integrate (mash up) different data sources, if the projections system, map scale and data quality match. The use of centralized data sources removes the burden for individual organizations to maintain copies of the same data sets. The downside is that one has to rely on and trust the external data sources.
Web maps allow for personalization. By using user profile, personal filters and personal styling and symbolization, users can configure and design their own maps, if the web mapping systems supports personalization. Accessibility issues can be treated in the same way. If users can store their favorite colors and patterns they can avoid color combinations they can't easily distinguish (e.g. due to color blindness). Web maps enable collaborative mapping. Similar to the Wikipedia project,, web mapping technologies, such as DHTML/Ajax, SVG, Java Adobe Flash ,etc. enable distributed data acquisition and collaborative efforts. Examples for such projects are the OpenStreetMaps project or the Google Earth community. As with other open projects, quality assurance is very important, however! Web maps support hyperliniking to other information on the web. Just like any other web pages or a wiki, web maps can act like an index to other information on the web. Any sensitive area in a map, a label text, etc. can provide hyperlinks to additional information. As an example a map showing public transport options can directly link to the corresponding section in the online train time table.
It is easy to integrate multimedia in and with web maps. Current web browser support the playback of video, audio and animation (SVG,SWF, Quick time, and other multimedia frameworks
Disadvantages of web maps and issues Reliability issues – the reliability of the internet and web server infrastructure is not yet good enough. Especially if a web map relies on external, distributed data sources, the original author often cannot guarantee the availability of the information.
Geodata are expensive – Unlike in the US, where geodata collected by governmental institutions is usually available for free or cheap, geodata is usually very expensive in Europe or other parts of the world.
Bandwidth issues – Web maps usually need a relatively high bandwidth.
Limited screen space – As with other screen based maps, web maps have the problem of limited screen space. This is in particular a problem for mobile web maps and location based services where maps have to be displayed in very small screens with resolutions as low as 100×100 pixels. Hopefully, technological advances will help to overcome these limitations.
Quality and accuracy issues – Many web maps are of poor quality, both in symbolization, content and data accuracy. Complex to develop – Despite the increasing availability of free and commercial tools to create web mapping and web
GIS applications, it is still a complex task to create interactive web maps. Many technologies, modules, services and data sources have to be mastered and integrated.
Immature development tools – Compared to the development of standalone applications with integrated development tools, the development and debugging environments of a conglomerate of different web technologies is still awkward and uncomfortable.
Copyright issues – Many people are still reluctant to publish geodata, especially in light of the fact that geodata are expensive in some parts of the world. They fear copyright infringements of other people using their data without proper requests for permission.
Privacy issues – With detailed information available and the combination of distributed data sources, it is possible to find out and combine a lot of private and personal information of individual persons. Properties and estates of individuals are now accessible through high resolution aerial and satellite images throughout the world to anyone.
History of web mapping
This section contains some of the milestones of web mapping, online mapping services and atlases.
1989-90: Birth of the WWW, WWW invented at CERN for the exchange of research documents. 1993-07: Xeror PARC Map Viewer The first map server based on CGI/Perl allowed reprojection styling and definition of map extent. 1994: The World Wide Earthquake Locator the first interactive web mapping mashup was released based on the Xerox PARC map view. 1994-06: The National Atlas of Canada The first version of the National Atlas of Canada was released. Can be regarded as the first online atlas. 1995: d The Gazetteer for Scotlan The prototype version of the Gazetteer for Scotland was released. The first geographical database with interactive mapping. 1995:MapGuide, First introduced as Argus Map Guide. 1996-02: , MapQuest The first popular online Address Matching and Routing Service with mapping output. 1996-06: MultiMap,The UK-based MultiMap website launched offering online mapping, routing and location based services. Grew into one of the most popular UK web sites. 1996-11: Geomedia Web Map 1.0, First version of GeoMedia, WebMap already supports vector graphics through the use of Active GM. 1996- MapGuide Autodesk acquired Argus Technologies and introduced Autodesk Map Guide 2.0.
1997-06: US Online National Atlas Initiative, The USGS received the mandate to coordinate and create the online National Atlas of United States America
1997-07: UMN MapServer1.0, Developed as Part of the NASA For Net Project. Grew out of the need to deliver remote sensing data across the web for foresters.
1997-10: - GeoInfoMapping , GeoInfo Solutions developed the first Java GIS Applet called GeoInfo 'Java Map'. The application supported the export and conversion of MapInfo data for display in the thematic mapping tool for the web. GeoinfoMapper was demonstrated at the Victoria Computer Show in 1997 and referenced in the Universal Locator project at UC Berkeley School of Information.
1998-08 Map object Internet Server entry into the web mapping business.
1999-08: National Atlas of Canada, 6th edition, This new version was launched at the ICA 1999 conference in Ottawa. Introduced many new features and topics. Is being improved gradually, since then, and kept up-to-date with technical advancements.
2000-02: ArcIMS 3.0, The first public release of ESRI's ArcIMS.
2000-06: ESRI Geography Network, ESRI founded Geography Network to distribute data and web map services. 2000-06: UMN Map Server 3.0, Developed as part of the NASA TerraSIP Project. This is also the first public, open source release of UMN Mapserver. Added raster support and support for TrueType fonts (Free Type). 2001 : GeoServer ,starts of the GeoServer project
2001-06: MapScript 1.0 for UMN MapServer, Adds a lot of flexibility to UMN Map Server solutions. 2001-09: Tirol atlas, A highly interactive online atlas, the first to be based on the SVG standard.
2002-06: UMN Map Server 3.5, Added support for postGIS Version 3.6 adds initial OGC WMS support.
2003-06: NASA World Wind Released, NASA World Wind Released. An open Virtual globe that loads data from distributed resources across the internet. Terrain and buildings can be viewed 3 dimensionally. The ( XML based) markup language allows users to integrate their own personal content. This virtual globe needs special software and doesn't run in a web browser. 2003-07: UMN MapServer 4.0, Adds 24bit raster output support and support for PDF. 2004-07: OpenStreetMap, Open Street Maps an open source, open content world map founded by Steve Coast. 2005-02: Google Maps ,The first version of Google Maps. Based on raster tiles organized in a quad tree scheme, data
2009-10 Nokia makes OviMaps free on its smart phones.
Web mapping technologies The potential number of technologies to implement web mapping projects is almost infinite. Any programming environment, programming language and serverside framework can be used to implement web mapping projects. In any case, both server and client side technologies have to be used. Following is a list of potential and popular server and client side technologies utilized for web mapping.
Spatial databases are usually object relational databases enhanced with geographic data types, methods and properties. They are necessary whenever a web mapping application has
to deal with dynamic data (that changes frequently) or with huge amount of geographic data. Spatial databases allow spatial queries, sub selects, reprojections, geometry manipulations and offer various import and export formats. A popular example for an open source spatial database is PostGIS. MYSQL also implements some spatial features, although not as mature as PostGIS. Commercial alternatives are Oracle Spatial or spatial extensions of Microsoft SQL Server and IBM DB2. The OGC Simple Features for SQL Specification is a standard geometry data model and operator set for spatial databases. Most spatial databases implement this OGC standard.
WMS severs can generate maps on request, using parameters, such as map layer order, styling/symbolization, map extent, data format, projection, etc. The OGC Consortium defined the WMS standard to define the map requests and return data formats, while other systems use standards like Tile Map Services for a similar purpose. Typical image formats for the map result are PNG, JPEG, GIF or SVG. There are open source WMS Servers such as UMN Map serve rand Map link. Commercial alternatives exist from most commercial GIS vendors, such as ESRI ArclMS and Cad Corps.
A virtual globe is a 3D Software model or representation of the Earth or another world. A virtual globe provides the user with the ability to freely move around in the virtual environment by changing the viewing angle and position. Compared to a conventional globe, virtual globes have the additional
capability of representing many different views on the surface of the Earth. These views may be of geographical features, man-made features such as roads and building , or abstract representations of demographic quantities such as population.
On November 20, 1997, Microsoft released a popular offline virtual globe in the form of Encarta Virtual Globe 98, followed by Cosmi’s 3D World Atlas in 1999. The first widely publicized online virtual globes were NASA World Wind (released in mid-2004) and Google Earth (mid-2005).
List of virtual globe software
As more and more high-resolution satellites imagery and aerial photography become accessible for free, many of the latest online virtual globes are built to fetch and display these images. They include:
NASA World Wind, USGS topographical maps and several satellite and aerial image datasets, the first popular virtual globe along with Google Earth. World Wind is open sources software . City Surf Globe, fast adaptation and transfer secured data due to special data storage structure, dynamic spatial data editing on 3D client monitor, data stored in Oracle SDO or PostGIS, flexible authorization models for different user groups (LDAP and Active Directory support) also excellent quality and fast 2D map rendering. Bing Maps 3D interface runs inside Internet Explorer and Firefox , and uses NASA Blue Marble: Next Generation.
Worldwide Telescope features an Earth mode with emphasis on data import/export, time-series support and a powerful Tour authoring environment. Google Earth ,satellite & aerial photos dataset (including commercial Digiral Globe images) with international road dataset, the first popular virtual globe along with NASA World Wind. Marble, part of the KDE, with data provided by OpenSteetMaps, as well as NASA Blue Marble: Next Generation and others. Marble is opensource software
ArcGIS Explorer a lightweight client for supports ArcGISserver WMS and many otherGIS file format .
Earth browser, a Adobe Flash/AIR-based virtual globe with realtime weather forecasts, earthquakes, volcanoes, and webcams. Earth3D, a program that visualizes the Earth in a real-time 3D view. It uses data from NASA, USGS, the CIA and the city of Osnabrück. Earth3D is open source software MapJack is a map feature covering areas in Canada, France, Latvia, Macau, Malaysia, Puerto Rico, Singapore, Sweden, Thailand, and the United States. Bhuvan is an India-specific virtual globe. Driveme.in is a street view application for India.
As well as the availability of satellite imagery, online public domain factual databases such as the have been Earth CIA world factbook incorporated into virtual globes.
Technical info, data, and image sources
Although by default the World Wind download only comes with public domain imagery from the USGS Community members have made available high resolution imagery for New Zealand and New York, and additional countries, as well as Microsoft's Virtual Earth data (for non-commercial purposes) Google Earth, NASA World Wind and Norkart Virtual Globe save a cache of downloaded imagery to the user's hard disk, enabling them to be used offline to view previously viewed areas. However, Google Earth cannot be activated without logging into its server the first time it is used. The Google Earth's cache size is limited to 2000 MB whereas World Wind has no limit on cache size. In Norkart Virtual Globe the disk cache can be set by the user. In addition to downloaded images, NASA World Wind also comes with the complete 500 m Blue Marble imagery and global placenames including countries, capitals, counties, cities, towns and historical references which are available from install. . Google Earth and Virtual Earth 3D are both capable of displaying many more urban areas in high-resolution thanks to their private image sources. Both companies also hire chartered flights over major cities of the U.S. to take aerial images. Marble (KDE) is designed for use in lightweight environments without 3D hardware acceleration and is capable of not only being used as a standalone application, but also as a component in other applications, such as in a "World Clock" Plasma(KDE) and for geolocation in the photo
management software digiKam . 3D Weather Globe & Atlas comes with complete 1 km Blue Marble imagery,40,000 locations database, countries and time zones overlays. Application requires Internet connection only for online features: satellite cloud cover and real-time weather and forecast data. Worldwide Telescope data support includes raster and vector types, the latter including up to 700,000 points in a single layer.. History The use of virtual globe software was widely popularized by may Neal Stephenson 's famous science fiction novel Snow Crash . In the metaverse in Snow Crash there is a piece of software called Earth made by the Central Intelligence Corporation. The CIC uses their virtual globe as a user interface for keeping track of all their geospatial data, including maps, architectural plans, weather data, and data from real-time satellite surveillance. Virtual globes (along with all hypermedia and virtual reality software) are distant descendants of the Aspen Movie Map project, which pioneered the concept of using computers to simulate distant physical environments (though the Movie Map's scope was limited to the city of Aspen Colorado. Many of the functions of virtual globes were envisioned by Buckminster Fuller who in 1962 envisioned the creation of a Geoscope which would be a giant globe connected by computers to various databases. This would be used as an educational tool to display large scale
Web GIS: Technologies Development of the web and expansion of internet provide too capabilities that can greatly help geoscientists .First the web allow visual interactive with data. By setting up the web serve client can produce maps since the maps and chart are published on the internet other client can view these updates helping to speed up the evaluation process. Because of the near nature of internet the geospatial data can be widely accessible. Client can work on it from almost any location. Both of these features altars the way geoscientists to their work in the very near future. The combination of easy access to data and visual presentation of it address some of the primary difficulties in performing geoscientists evaluation web GIS is not without its faults.
Connection speeds over the internet can make heavy use of graphics into learly slow for user. Transferred Geo Data: Except attribute data a decisive question for using GIS in the internet is the data format when is used to transfer data to client for data transmission to the client map is converted in to no space raster or a suitable vector format. When raster data is transferred a standards web browser without extension can be used since web browser displays GIF and JPEG. That means the data on the server has to be converted to a raster format. The data volume due to the known images size and the server safe as only an images is sent to the client. Disadvantaged of using raster data in the lack of comfort of handling and regarding cartographic aspect like font problem. Vector data handled by standards web browser with extended functionality. The user gets a more functionality with vector data . One more advantage of using vector data is the possibilities of local processing it is not necessary to contact the server per executed browser action. Different consortia are developing future standards format for transferring data over the internet. The open GIS consortium, example present, Geography Markup Language (GML) shall enable the transport and storage of geographical informational in Xtensible Markup Language (XML).The W3C submits scalable vector graphics which is a language for describing two demiensial vector and mixed vector graphics in XML.
Interactive Web Maps
There are several technology level to publish map data on the web ranging from sites that simply publish static web maps to more sophisticated site which support dynamic maps interactively customized maps and multiple computer platform and operating system. The Web GIS the most challenges maps is the interactive one. Within the open GIS consortium a special interest for WWW mapping is working on issue of Web-based GIS publishing. The interactive model has four tiers: 1.Selection process retrieve data from a geospatial data sources according to query constraints such as search area or thematic selection . 2. The display elements generator process turn the selected geospatial data into a sequence of this elements . 3. The render takes the display elements and generates a rendered map. 4. The display process makes the render maps visible to the user on a suitable display devices .
Internet Map Server IMS applications allow GIS database custodian to easily make their spatial data accessible through a web browser interface end-user. High speed corporate intranet make an ideal network for distributing data in this manner given the fact that bandwidth requirements can be high.
Web GIS Architecture In performing the GIS analysis takes web GIS is similar to the client /server typical three tier architecture. The geographic processing is breaking down into server side and client side tasks. The client typical is a web browser . The server side consist of a web server ,webGIS software and database.
The model of network widely exist within enterpriser in which some computer act as client. Server simply have the proprietary GIS running and add a client interface at the client side and a middleware at the server side to communicate network the client and the proprietary GSI software .
Thin Client Architecture The thin Client Architecture is used in typical architecture. In a thin client system the client only have user interface to
communicate with the server and display the results .All the processing is done on the server actually shows in figure 2. The server computer usually have more power then the client and manage the centralized resources . Figure 3 show schematic communication web server ,web browser and GIS. Web server side there are some possibilities to realize the GIS connection to WWW CGI,API(Application programming Interface ),JSP(Java server page) and ASP(Active server page) etc.
Thin client server approach has following advantages:a) Central Control b) Easy for data version c) Generally cheaper d) Integration possibilities e) Regarding some cartographic aspects such font. •Thin client server approach has following disadvantages:a) Large data volume, b) Slow response time, c) Less interactive, and d) No local accountability
Thick Client Architecture In general a web browser can handle HTML documents and embedded raster image in the standards format. To deal with there data format vector data , video clips, music file, the browser functionality has to be extended using exactly the same same client server communication Thin vector files format could not be used. To overcome this problem must browser applications offer a mechanism that allow third tier program to work together with the browser as a plug in. This progress is follow : HTML CGI, using HTML form and CGI, Java script increase user interface capabilities, Java applet to provide client side function .
Thick client server approach has following advantages:a) Document/graphics standards are not required.
b) Vector data can be used. c) Image quality not restricted to GIF and JPEG. d) Modern interface is possible; it is not restricted to single–click operations. •Thick client server approach has following disadvantages:a) Additional software requirement, and b) Platform/browser in compatibility
Distributed Web GIS •Distributed Web GIS architecture is modular and allows the publishing of web service descriptions. •Distributed GIS service mode list that client program in either an browser or an independent application, able to access the distributed resources in the entire network. •Client connect to the several servers if needed and a specific machine may be the client at one time and the server at an other time. •Ideal distributed GIS service model is “Geo data anywhere, Geo processing anywhere”.
Service Oriented Architecture
In recent years the technology trend within information technology has made it possible to move towards service oriented architectures and distributed computing.There are lots of services available over the internet. However it is not possible for individual standalone service to meet all the service requirements of many users. As the number of geospatial services increased rapidly, an emerging need has also appeared for methodologies to locate desired services that provide access and data mining capabilities to geospatial data. The Service Oriented Architecture (SOA) recognizes this and tries to construct a distributed, dynamic, flexible, and reconfigurable service system over Internet that can meet information and service requirements of many different users.SOA is an architectural style for building software applications that use services available in a network such as the Web. SOA is a principle concept underlying beneath Web Services implementation. It promotes loose coupling between software components so that they can be reused. The key component in the SOA is service. SOA concept has three components service provider, service registry, service requester and three operations: publish, find, and bind. A SOA relates the roles of the three components with the three operations to maintain automated discovery and the use of services. The three essential components mentioned above can be described as following: • Service provider publishes services to a registry and makes it available on the Internet for the requests of the consumers. • Service requester (client) performs service discovery operations on the service registry in order to find the needed service; then accesses services.
• Service registry helps service providers and service requesters to find each other by acting as a registry of the services (Sayar, 2008).
Benefits of Service Oriented Architecture
The benefits of SOA are several. From users‟ perspective, a SOA setting is an open and interoperable environment, which is based on reusability and standardized components. Basically a SOA creates an infrastructure for application development. Development is focused towards concrete applications and in contrast to standard GIS applications where normally only a small percentage of the functionalities in the software are used, applications based on SOA provide users with just the functionality they need. Another prominent intention of the design of a SOA is that data used for a given processing activity are not stored locally, but rather decentralized close to the source of production. The SOA approach to system development can produce systems that can be flexibly adapted to changing requirements and technologies, and offers easier maintainable and more consistent systems of data and functionality. Provide three type of different services. These are a) Data Service, b) Processing Service and c) Registry Service. • Data Services: are tightly coupled with specific data sets and offer access to customized portions of that data. Web Feature Service (WFS), Web Feature Service-Transactional (WFS-T), Web Mapping Service (WMS) and Web Coverage Service (WCS) can be considered in this group. WMS produces maps as two-dimensional visual portrayals of geospatial data. WCS provides access to un-rendered geospatial information (raster data). WFS provides geospatial feature data (vector
data) encoded in Geography Markup Language (GML) whereas WFS-T enables editing feature coordinate geometry (i.e position and shape) and related descriptive information (i.e. attribute values), as well. •Processing Services provide operations for processing or transforming data in a manner determined by user-specific parameters. They provide generic processing functions such as projection and coordinate conversion, rasterization and vectorization. Coverage Portrayal Service (CPS), Coordinate Transformation Service (CTS), and even WMS can be considered in this group. • Registry or Catalog Service allows users and applications to classify, register, describe, search, maintain, and access information about Web Services. Web Registry Service (WRS) and Catalog Service for the Web (CS-W) are considered in this group .
Open Source Technology
Open source program allow user to modify source code according to their requirement. Provides better interoperability. Open Geospatial Consortium,(OGC) is a international, voluntary consensus standards organization that is leading the development of standards for geo spatial and location based services.
Web Features Service (WFS), defines web interfaces for accessing feature-based geospatial data (vector data like administrative and political information, streets, cities, etc). WFS allows a client to retrieve and update geospatial data encoded in GML from multiple Web Feature Services. The specification defines interfaces for data access and
manipulation operations on geographic features, using HTTP as the distributed computing platform. Via these interfaces, a Web user or service can combine, use and manage geospatial data -- the feature information behind a map image -- from different sources. • Web Map Service (WMS) produces maps of spatially referenced data dynamically from geographic information. This service defines a “map” to be a portrayal of geographic information as a digital image file suitable for display on a computer screen. • Web Coverage Service (WCS) represents a web interface for supporting electronic retrieval of geospatial data as "coverages" – that is, digital geospatial information (like remotely sensed imagery, ortho-photos, etc) representing space-varying phenomena. A WCS provides access to potentially detailed and rich sets of geospatial information, in forms that are useful for client-side rendering and input into scientific models and other clients. • Web Registry Service (WRS) specifies web interfaces for finding data or services from registries. GML is widely accepted as the universal encoding