Distributed GIS concerns itself with GI Systems that do not have all of the system components in the same physical location. This could be the processing
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...
. Examples of distributed systems are web-based GIS, Mobile GIS, Corporate GIS and GRID computing
Grid computing
Grid computing is a term referring to the combination of computer resources from multiple administrative domains to reach a common goal. The grid can be thought of as a distributed system with non-interactive workloads that involve a large number of files...
The University of Edinburgh, founded in 1583, is a public research university located in Edinburgh, the capital of Scotland, and a UNESCO World Heritage Site. The university is deeply embedded in the fabric of the city, with many of the buildings in the historic Old Town belonging to the university...
. He was responsible for one of the first Internet-based distributed GIS. 1n 1994, he designed and implemented the World Wide Earthquake Locator, which provided maps of recent earthquake occurrences to a location-independent user, which used the Xerox PARC mapping system (based in California, USA), managed by an interface based in Edinburgh (Scotland), which drew data in real-time from the National Earthquake Information Center (USGS) in Colorado, USA . Gittings first taught a course in this subject in 2005 as part of the Masters Programme in GIS at that institution. There being no Wikipedia article relating to Distributed GIS, he set his students the task of creating one in 2007 as a class exercise.
Corporate GIS
A corporate Geographical Information System, is similar to Enterprise GIS (see below) and satisfies the spatial information needs of an organisation as a whole in an integrated manner (Chan & Williamson 1997). Corporate GIS consists of four technological elements which are data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
Information technology is the acquisition, processing, storage and dissemination of vocal, pictorial, textual and numerical information by a microelectronics-based combination of computing and telecommunications...
and personnel with expertise. It is a coordinated approach that moves away from fragmented desktop GIS. The design of a corporate GIS includes the construction of a centralised corporate database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
that is designed to be the principle resource for an entire organisation.
The corporate database is specifically designed to efficiently and effectively suit the requirements of the organisation. Essential to a corporate GIS is the effective management of the corporate database and the establishment of standards such as OGC
OGC
OGC may refer to:* Oculogyric crisis, a dystonic reaction to certain drugs and/or medical conditions* Office of Government Commerce, a department of the government of the United Kingdom...
for mapping and database technologies.
Benefits
There are many advantages of a corporate GIS. Firstly, all the users in the organisation have access to shared, complete, accurate, high quality and up-to-date data. All the users in the organisation also have access to shared technology and people with expertise. Consequently, this improves the efficiency and effectiveness of the organisation as a whole. A successfully managed corporate database reduces redundant collection and storage of information across the organisation. By centralising resources and efforts, it reduces the overall cost.
Recommended use
A corporate GIS is recommended for anyone from local governments to global governmental organisations. This is particularly useful if data is to be shared between governmental departments or organisations. However, a corporate GIS is considered not to be cost efficient for smaller organisations as it is expensive to implement.
A geographic information system, geographical information science, or geospatial information studies is a system designed to capture, store, manipulate, analyze, manage, and present all types of geographically referenced data...
from the office into the field. This is heavy reliant upon wireless technologies to access remotely stored data. Mobile GIS may be based on toughened laptops or tablet PCs and have all or some of the functions of a desktop GIS. There are smaller PDA based systems, which have a more limited but often tailored set of functions. They allow the capture, manipulation and storage of data in remote locations. This has the advantage of real time updating of central databases, thus removing the need for storage of multiple copies of data and lessening data replication.
Those that are reliant on real time data transfer are generally dependent upon the GSM networks and are limited to the bandwidths of these networks.
Device Limitations
Although not all applications of mobile GIS are limited by the device, many are. These limitations are more applicable to smaller devices such as cell phones and PDAs. Such devices have:
small screens with a poor resolution
limited memory and processing power
a poor (or no) keyboard
short battery life
Enterprise GIS
Enterprise GIS refers to a geographical information system that integrates geographic data across multiple departments and serves the whole organisation (ESRI, 2003). The basic idea of an enterprise GIS is to deal with departmental needs collectively instead of individually. When organisations started using GIS in the 1960s and 1970s, the focus was on individual projects where individual users created and maintained data sets on their own desktop computers. Due to extensive interaction and work-flow between departments, many organisations have in recent years switched from independent, stand-alone GIS systems to more integrated approaches that share resources and applications (Ionita, 2006).
Some of the potential benefits that an enterprise GIS can provide include significantly reduced redundancy of data across the system, improved accuracy and integrity of geographic information, and more efficient use and sharing of data (Sipes, 2005). Since data is one of the most significant investments in any GIS program, any approach that reduces acquisition costs while maintaining data quality is important. The implementation of an enterprise GIS may also reduce the overall GIS maintenance and support costs providing a more effective use of departmental GIS resources. Data can be integrated and used in decision making processes across the whole organisation (Sipes, 2005).
Strategy
The development of the European Union (EU) ’’’INSPIRE’’’ initiative indicates this is a matter that is gaining more awareness at the national and EU scale. This states that there is a need to create ‘quality geo-referenced information’ that would be useful for a better understanding of human activities on environmental processes. Therefore it is an ambitious project that aims to develop a European spatial information database.
The GI strategy for Scotland was introduced in 2005 to provide a sustainable SDI, through the ’’One Scotland – One Geography’’ implementation plan. This documentation notes that it should be able to provide linkages to the ’’Spaces, Faces and Places of Scotland’’.
Although plans for a GI strategy have been in existence for some time, it was revealed at the AGI Scotland 2007 conference that a recent budget review by the Scottish Government indicated there will not be an allocation of resources to fund this initiative within the next term. Therefore a business plan will need to be presented in order to outline the cost-benefits involved with taking up the strategy.
The Open Geospatial Consortium , an international voluntary consensus standards organization, originated in 1994. In the OGC, more than 400 commercial, governmental, nonprofit and research organizations worldwide collaborate in a consensus process encouraging development and implementation of open...
(OGC). OGC is a non-profit international group which seeks to Web-Enable GIS and in turn Geo-Enable the web. One of the major issues concerning distributed GIS is the interoperability of the data since it can come in different formats using different projection systems. OGC standards seek to provide interoperability between data and to integrate existing data.
OGC
In terms of interoperability, the use of communication standards in Distributed GIS is particularly important. General standards for Geospatial
Geospatial
Geospatial analysis is an approach to applying statistical analysis and other informational techniques to geographically based data. Such analysis employs spatial software and analytical methods with terrestrial or geographic datasets, including geographic information systems and...
Data have been developed by the Open Geospatial Consortium (OGC)
Open Geospatial Consortium
The Open Geospatial Consortium , an international voluntary consensus standards organization, originated in 1994. In the OGC, more than 400 commercial, governmental, nonprofit and research organizations worldwide collaborate in a consensus process encouraging development and implementation of open...
. For the exchange of Geospatial Data over the web, the most important OGC standards are Web Map Service (WMS
Web Map Service
A Web Map Service is a standard protocol for serving georeferenced map images over the Internet that are generated by a map server using data from a GIS database...
The Open Geospatial Consortium Web Feature Service Interface Standard provides an interface allowing requests for geographical features across the web using platform-independent calls...
).
Using OGC compliant gateways allows for building very flexible Distributed GI Systems. Unlike monolithic GI Systems, OGC compliant systems are naturally web-based and do not have strict definitions of servers
Server (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...
A client is an application or system that accesses a service made available by a server. The server is often on another computer system, in which case the client accesses the service by way of a network....
) accesses a server, that server itself can act as a client of a number of further servers in order to retrieve data requested by the user
User (computing)
A user is an agent, either a human agent or software agent, who uses a computer or network service. A user often has a user account and is identified by a username , screen name , nickname , or handle, which is derived from the identical Citizen's Band radio term.Users are...
. This concept allows for data retrieval from any number of different sources, providing consistent data standards are used.
Furthermore, this concept allows data transfer with systems not capable of GIS functionality. A key function of OGC standards
Open Geospatial Consortium
The Open Geospatial Consortium , an international voluntary consensus standards organization, originated in 1994. In the OGC, more than 400 commercial, governmental, nonprofit and research organizations worldwide collaborate in a consensus process encouraging development and implementation of open...
is the integration of different systems already existing and thus geo-enabling the web. Web service
Web service
A Web service is a method of communication between two electronic devices over the web.The W3C defines a "Web service" as "a software system designed to support interoperable machine-to-machine interaction over a network". It has an interface described in a machine-processable format...
s providing different functionality can be used simultaneously to combine data from different sources (mash-ups). Thus, different services on distributed servers can be combined for ‘service-chaining’ in order to add additional value to existing services. Providing a wide use of OGC standards by different web services, sharing distributed data of multiple organisations becomes possible.
Other standards
Some important languages used in OGC compliant systems are described in the following. XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
stands for eXtensible Markup language and is widely used for displaying and interpreting data from computers. Thus the development of a web-based GI system requires several useful XML encodings that can effectively describe two-dimensional graphics such as maps SVG and at the same time store and transfer simple features GML
GML
GML may refer to:* Middle Low German , a language used around the North Sea and the Baltic Sea from 1100 to 1600* Gostomel Airport , an international cargo airport, near Kiev, Ukraine* Gradient Multi-Layer nano-film...
. Because GML and SVG are both XML encodings, it is very straightforward to convert between the two using an XML Style Language Transformation XSLT
XSLT
XSLT is a declarative, XML-based language used for the transformation of XML documents. The original document is not changed; rather, a new document is created based on the content of an existing one. The new document may be serialized by the processor in standard XML syntax or in another format,...
. This gives an application a means of rendering GML, and in fact is the primary way that it has been accomplished among existing applications today. XML can introduce innovative web services, in terms of GIS. It allows geographic information to be easily translated in graphic and in these terms scalar vector graphics (SVG) can produce high quality dynamic outputs by using data retrieved from spatial databases. In the same aspect Google, one of the pioneers in web-based GIS, has developed its own language which also uses a XML structure. Keyhole Markup Language or KML
KML
KML or kml may refer to:* Kamileroi Airport , Queensland, Australia* Keyhole Markup Language, an XML geospatial data file format...
is a file format used to display geographic data in an earth browser, such as Google Earth, Google Maps, and Google Maps for mobile browsers
Global System for Mobile Communications
It is a global standard for mobile phones around the world. Networks using the GSM system offer transmission of voice, data and messages in text and multimedia form and provide web, telenet, ftp, email services etc. over the mobile network. Almost two million people are now using GSM. Five main standards of GSM exist: GSM 400, GSM 850, GSM 900, GSM-1800 (DCS) and GSM1900 (PCS). GSM 850 and GSM 1900 is used in North America, parts of Latin America and parts of Africa. In Europe, Asia and Australia GSM 900/1800 standard is used.
A subscriber identity module or subscriber identification module is an integrated circuit that securely stores the International Mobile Subscriber Identity and the related key used to identify and authenticate subscriber on mobile telephony devices .A SIM is held on a removable SIM card, which...
. GSM is a cellular network, which is a radio network made up of a number of cells. For each cell, the transmitter (known as a base station) is transmitting and receiving signals. The base station is controlled through the Base Station Controller via the Mobile Switching Centre.
General packet radio service is a packet oriented mobile data service on the 2G and 3G cellular communication system's global system for mobile communications . GPRS was originally standardized by European Telecommunications Standards Institute in response to the earlier CDPD and i-mode...
Universal Mobile Telecommunications System is a third generation mobile cellular technology for networks based on the GSM standard. Developed by the 3GPP , UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for...
3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 specifications by the International Telecommunication Union...
) mobile communication system. Both provide similar services to 2G, but with greater bandwidth and speed.
Wireless Application Protocol
This is a standard for the data transmission of internet content and services. It is a secure specification that allows users to access the information instantly via mobile phones, pagers, two-way radios, smartphones and communicators. WAP supports HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
WML may stand for:* What's My Line?, a game show* White matter lesion, a lesion of the white matter* Wireless Markup Language, markup used for mobile phones with Wireless Application Protocol* Website Meta Language, Unix software for HTML generation...
language, and is specifically designed for small screens and one-hand navigation without a keyboard. WML is scalable from two-line text displays up to the graphical screens found on smart phones. It is much stricter than HTML and is similar to JavaScript.
A Location-Based Service is an information or entertainment service, accessible with mobile devices through the mobile network and utilizing the ability to make use of the geographical position of the mobile device....
(LBS) are services that are distributed wirelessly and provide information relevant to the user’s current location. These services include such things as ‘find my nearest …’, directions, and various vehicle monitoring systems, such as the GM OnStar system
OnStar
OnStar Corporation is a subsidiary of General Motors that provides subscription-based communications, in-vehicle security, hands free calling, turn-by-turn navigation, and remote diagnostics systems throughout the United States, Canada and China. A similar service is known as ChevyStar in Latin...
amongst others. Location based services are generally run on mobile phones and PDAs, and are intended for use by the general public more than Mobile GIS systems which are geared towards commercial enterprise. Devices can be located by triangulation using the mobile phone network and/or GPS.
Device limitations are similar to those for mobile GIS. In addition, any devices that are reliant on WAP will be limited by WAP functionality.
HTML
HTML, an initialism of Hypertext Markup Language, is the predominant markup language
Markup language
A markup language is a modern system for annotating a text in a way that is syntactically distinguishable from that text. The idea and terminology evolved from the "marking up" of manuscripts, i.e. the revision instructions by editors, traditionally written with a blue pencil on authors' manuscripts...
A web page or webpage is a document or information resource that is suitable for the World Wide Web and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext...
s. It provides a means to describe the structure of text-based information in a document — by denoting certain text as headings, paragraphs, lists, and so on — and to supplement that text with interactive forms, embedded images, and other objects. HTML is written in the form of labels (known as tags), surrounded by angle brackets. HTML can also describe, to some degree, the appearance and semantics
Semantics
Semantics is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs and symbols, and what they stand for, their denotata....
A scripting language, script language, or extension language is a programming language that allows control of one or more applications. "Scripts" are distinct from the core code of the application, as they are usually written in a different language and are often created or at least modified by the...
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...
s and other HTML processors.
HTML is also often used to refer to content of the MIME type text/html or even more broadly as a generic term for HTML whether in its XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
XHTML is a family of XML markup languages that mirror or extend versions of the widely-used Hypertext Markup Language , the language in which web pages are written....
1.0 and later) or its form descended directly from SGML (such as HTML 4.01 and earlier).
Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
.
Perl is a general-purpose programming language originally developed for text manipulation and now used for a wide range of tasks including system administration, web development, network programming, GUI development, and more.
The language is intended to be practical (easy to use, efficient, complete) rather than beautiful (tiny, elegant, minimal).[3] Its major features include support for multiple programming paradigms (procedural, object-oriented, and functional styles), automatic memory management, built-in support for text processing, and a large collection of third-party modules.
Geotagging
Geotagging is the process of adding geographical identification metadata to resources such as websites, RSS feed, images or videos. The metadata usually consist of latitude and longitude coordinates but may also include altitude, camera holding direction, place information and so on. Flickr website is one of the famous web services which host photos and provides functionality to add latitude and longitude information to the picture.
The main idea is to use metadata related to pictures and photo collection. A geotag is simply a properly-formed XML tag giving the geographic coordinates of a place. The coordinates can be specified in latitude and longitude or in UTM (Universal Transverse Mercator) coordinates. The RDFIG Geo vocabulary from the W3C is the common basis for the recommendations. It supplies official global names for the latitude, longitude, and altitude properties. These are given in a system of coordinates known as "the WGS84 datum". (A geographic datum specifies an ellispoidal approximation to the Earth's surface; WGS84 is the most commonly used such datum; it is utilized, e.g. for GPS).
To specify that the longitude of something is X, that its latitude is Y, and, optionally, that its altitude is Z, tags form of the tags used is X Y Z
Altitude is specified in meters. The prefix "geo:" represents the RDFIG Geo namespace, whose URL is: http://www.w3.org/2003/01/geo/wgs84_pos#.
Geotagging an HTML element
The following tag will pass muster as correct XML in the context of XHTML (the newer dialect of HTML that adheres to the XML standard), but will also work in earlier HTML dialects, in the sense of being tolerated by all modern browsers. To geotag an HTML element, include a span of the following form: 46.1 124
If the geo namespace is defined at an outer level of the document, the namespace definition in the span tag can be omitted, leaving 46.1124
In earlier HTML dialects, omitting the namespace definition is also appropriate, since the objective of adhering to the XML standard is irrelevant.
This technique can be used to geotag a post in a weblog, or elements within any HTML document.
Geotagging XML (including RSS and RDF).
In XML simply elements of the form
46.1 124
are included as children of the element one wish to tag, and place the definition of the geo namespace at the outermost level of the document.
Geotagging a web page
Following method is used to assign a location to a web page as a whole, rather than to its parts. In the element, following metatags are included:
46.1
124
In XHTML, the document namespace definition should include the geo tag.
This form of meta tag follows the recommendations contained in http://www.w3.org/MarkUp/2004/02/xhtml-rdf.html
In distributed GIS, the term mashup refers to a generic web service which combines content and functionality from disparate sources; mashups reflect a separation of information and presentation. Mashups are increasingly being used in commercial and government applications as well as in the public domain.
When used in GIS, it reflects the concept of connecting your application with a mapping service (e.g., combining Google maps
Google Maps
Google Maps is a web mapping service application and technology provided by Google, free , that powers many map-based services, including the Google Maps website, Google Ride Finder, Google Transit, and maps embedded on third-party websites via the Google Maps API...
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
crime statistics to create the [www.chicagocrime.org/map/ Chicago crime statistics map]).
Mashups are fast, provide value for money and remove responsibility for the data from the creator.
Second generation systems provide mashups mainly based on URL parameters, while Third generation systems (e.g. Google Maps
Google Maps
Google Maps is a web mapping service application and technology provided by Google, free , that powers many map-based services, including the Google Maps website, Google Ride Finder, Google Transit, and maps embedded on third-party websites via the Google Maps API...
) allow customisation via script (e.g. JavaScript).
Web Mapping Services
A web mapping service is a means of displaying and interacting with maps on the Web. The first web mapping service was the Xerox PARC Map Viewer
Xerox PARC Map Viewer
Xerox PARC Map Viewer was one of the earliest static web mapping sites, developed by Steve Putz in June 1993 at Xerox Corporation's Palo Alto Research Center...
A Web Map Service is a standard protocol for serving georeferenced map images over the Internet that are generated by a map server using data from a GIS database...
. The first generation was from 1993 onwards and consisted of simple image maps which had a single click function. The second generation was from 1996 onwards and still used image maps the one click function. However, they also had zoom and pan capabilities (although slow) and could be customised through the use of the URL API. The third generation was from 1998 onwards and were the first to include slippy maps. They utilise AJAX
Ajax (programming)
Ajax is a group of interrelated web development methods used on the client-side to create asynchronous web applications...
technology which enables seamless panning and zooming. They are customisable using the URL API and can have extended functionality programmed in using the DOM
DOM
DOM may refer to:*D.O.M. , a restaurant in São Paulo, Brazil*Days on market, how many days since a piece of real estate was listed for sale*Deo optimo maximo, Latin for "to the Greatest and Best God", originally Jove, later the Christian God...
.
Web map services are based on the concept of the image map
Image map
In HTML and XHTML , an image map is a list of coordinates relating to a specific image, created in order to hyperlink areas of the image to various destinations . For example, a map of the world may have each country hyperlinked to further information about that country...
whereby this defines the area overlaying an image (e.g. GIF). An image map
Image map
In HTML and XHTML , an image map is a list of coordinates relating to a specific image, created in order to hyperlink areas of the image to various destinations . For example, a map of the world may have each country hyperlinked to further information about that country...
can be processed client or server side. As functionality is built into the web server, performance is good. Image maps can be dynamic. When image maps are used for geographic purposes, the co-ordinate system must be transformed to the geographical origin to conform to the geographical standard of having the origin at the bottom left corner.
A Location-Based Service is an information or entertainment service, accessible with mobile devices through the mobile network and utilizing the ability to make use of the geographical position of the mobile device....
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
has gone far beyond the average persons thinking. It is not only chatting or just surfing the web but it is a new way of connecting people and how to bring the experience from a desktop to the browser which will be more user friendly. For this reason some Rich Internet Applications (RIA)
Rich Internet application
A Rich Internet Application is a Web application that has many of the characteristics of desktop application software, typically delivered either by way of a site-specific browser, via a browser plug-in, independent sandboxes, extensive use of JavaScript, or virtual machines...
Ajax is a group of interrelated web development methods used on the client-side to create asynchronous web applications...
is one of the widely used terms in this context in conjunction with flash
Adobe Flash
Adobe Flash is a multimedia platform used to add animation, video, and interactivity to web pages. Flash is frequently used for advertisements, games and flash animations for broadcast...
-Computing:* Adobe Flex, technologies for developing rich internet applications* Flex, a family of automatic test equipment produced by Teradyne* Flex lexical analyser, a free software alternative to lex* Flex machine, multiple systems...
Nexaweb offers application modernization software and services that target client/server applications developed using popular 4GL tools such as PowerBuilder...
The term Web 2.0 is associated with web applications that facilitate participatory information sharing, interoperability, user-centered design, and collaboration on the World Wide Web...
application tends to interact with the end user and the end user had a greater role in the web 2.0
Web 2.0
The term Web 2.0 is associated with web applications that facilitate participatory information sharing, interoperability, user-centered design, and collaboration on the World Wide Web...
applications as he/she is not only the user of the application but also a participant. This may be through tagging
Tag (metadata)
In online computer systems terminology, a tag is a non-hierarchical keyword or term assigned to a piece of information . This kind of metadata helps describe an item and allows it to be found again by browsing or searching...
A wiki is a website that allows the creation and editing of any number of interlinked web pages via a web browser using a simplified markup language or a WYSIWYG text editor. Wikis are typically powered by wiki software and are often used collaboratively by multiple users. Examples include...
A podcast is a series of digital media files that are released episodically and often downloaded through web syndication...
or blogging. The user also provides feedback on the applications in addition to their social contribution to the applications.
One of the key components of web 2.0 are web services, and how these applications expose their functionality and can be combined with other applications to provide a rich set of new applications using mashups
Mashup (digital)
A digital mashup usually is in reference to:1. Digital media content containing any or all of text, graphics, audio, video and animation drawn from pre-existing sources, to create a new derivative work...
. Computer languages are required to perform these tasks, and it is very important to update the applications frequently so the many users get up to date information. Some of the applications of web 2.0
Web 2.0
The term Web 2.0 is associated with web applications that facilitate participatory information sharing, interoperability, user-centered design, and collaboration on the World Wide Web...
Flicker may refer to any of the following:* Flickers, woodpeckers of the subgenus Colaptes* Flicker , a fading between frames that occurs on a cathode-ray screen at low refresh rates...
Delicious is a social bookmarking web service for storing, sharing, and discovering web bookmarks. The site was founded by Joshua Schachter in 2003 and acquired by Yahoo! in 2005, and by the end of 2008, the service claimed more than 5.3 million users and 180 million unique bookmarked URLs...
Facebook is a social networking service and website launched in February 2004, operated and privately owned by Facebook, Inc. , Facebook has more than 800 million active users. Users must register before using the site, after which they may create a personal profile, add other users as...
Myspace is a social networking service owned by Specific Media LLC and pop star Justin Timberlake. Myspace launched in August 2003 and is headquartered in Beverly Hills, California. In August 2011, Myspace had 33.1 million unique U.S. visitors....
.
Performance
The speedup of a program as a result of parallelization is given by Amdahl's law
Amdahl's law
Amdahl's law, also known as Amdahl's argument, is named after computer architect Gene Amdahl, and is used to find the maximum expected improvement to an overall system when only part of the system is improved...
.
Amdahl's Law states that potential program speedup is defined by the fraction of code (P) that can be parallelized: 1/(1-P)
If the code cannot be broken up to run over multiple processors, P = 0 and the speedup = 1 (no speedup). If it is possible to break up the code to be perfectly parallel then P = 1 and the speedup is infinite (in theory, although other factors such as scalability and complexity limit this possibility). Thus, there is an upper bound on the usefulness of adding more parallel execution units. http://www.llnl.gov/computing/tutorials/parallel_comp/
Gustafson's Law is a law in computer science which says that problems with large, repetitive data sets can be efficiently parallelized. Gustafson's Law contradicts Amdahl's law, which describes a limit on the speed-up that parallelization can provide. Gustafson's law was first described by John...
is a law closely related to Amdahl's law but doesn’t make as many assumptions and tries to model these factors in the representation of performance. The equation can be modelled by S(P) = P − α * (P − 1) where P is the number of processors, S is the speedup, and α the non-parallelizable part of the process.
Parallel processing is the ability to carry out multiple operations or tasks simultaneously. The term is used in the contexts of both human cognition, particularly in the ability of the brain to simultaneously process incoming stimuli, and in parallel computing by machines.-Parallel processing by...
is the use of multiple CPU’s to execute different sections of a program together. Remote sensing
Remote sensing
Remote sensing is the acquisition of information about an object or phenomenon, without making physical contact with the object. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth by means of propagated signals Remote sensing...
and surveying equipment have been providing vast amounts of spatial information, and how to manage, process or dispose of this data have become major issues in the field of Geographic Information Science
Geographic Information Science
Geographic information science is the academic theory behind the development, use, and application of geographic information systems...
(GIS).
To solve these problems there has been much research into the area of parallel processing of GIS information. This involves the utilization of a single computer with multiple processors or multiple computers that are connected over a network working on the same task. There are many different types of distributed computing, two of the most common are clustering and grid processing.
Why Use Parallel Processing
The primary reasons for using parallel computing:
Save time - wall clock time
Solve larger problems
Provide concurrency (do multiple things at the same time)
Other reasons might include:
Taking advantage of non-local resources - using available computing resources on a wide area network, or even the Internet when local computing resources are scarce.
Cost savings - using multiple "cheap" computing resources instead of paying for time on a supercomputer.
Overcoming memory constraints - single computers have very finite memory resources. For large problems, using the memories of multiple computers may overcome this obstacle.
Limits to serial computing - both physical and practical reasons pose significant constraints to simply building ever faster serial computers:
Transmission speeds - the speed of a serial computer is directly dependent upon how fast data can move through hardware. Absolute limits are the speed of light (30 cm/nanosecond) and the transmission limit of copper wire (9 cm/nanosecond). Increasing speeds necessitate increasing proximity of processing elements.
Limits to miniaturization - processor technology is allowing an increasing number of transistors to be placed on a chip. However, even with molecular or atomic-level components, a limit will be reached on how small components can be.
Economic limitations - it is increasingly expensive to make a single processor faster. Using a larger number of moderately fast commodity processors to achieve the same (or better) performance is less expensive.
The future: during the past 10 years, the trends indicated by ever faster networks, distributed systems, and multi-processor computer architectures (even at the desktop level) clearly show that parallelism is the future of computing.
Grid Computing
Some consider this to be “the third information technology wave” after the Internet and Web, and will be the backbone of the next generation of services and applications that are going to further the research and development of GIS and related areas.
Grid computing allows for the sharing of processing power, enabling the attainment of high performances in computing, management and services. Grid computing, (unlike the conventional supercomputer that does parallel computing by linking multiple processors over a system bus) uses a network of computers to execute a program. The problem of using multiple computers lies in the difficulty of dividing up the tasks among the computers, without having to reference portions of the code being executed on other CPUs.
Local search is the use of specialized Internet search engines that allow users to submit geographically constrained searches against a structured database of local business listings...
Local Search is a recent approach to internet searching that incorporates geographical information into search queries so that the links that you return are more relevant to where you are. It developed out of an increasing awareness that many search engine
Search engine
A search engine is an information retrieval system designed to help find information stored on a computer system. The search results are usually presented in a list and are commonly called hits. Search engines help to minimize the time required to find information and the amount of information...
users are using it to look for a business or service in the local area. Local search has stimulated the development of web mapping, which is used either as a tool to use in geographically restricting your search (see Live Search Maps) or as an additional resource to be returned along with search result listings (see Google Maps
Google Maps
Google Maps is a web mapping service application and technology provided by Google, free , that powers many map-based services, including the Google Maps website, Google Ride Finder, Google Transit, and maps embedded on third-party websites via the Google Maps API...
). It has also led to an increase in the number of small businesses
advertising on the web.
The Automatic Identification System is an automatic tracking system used on ships and by Vessel traffic services for identifying and locating vessels by electronically exchanging data with other nearby ships and AIS Base stations...
A spatial data infrastructure is a framework of spatial data, metadata, users and tools that are interactively connected in order to use spatial data in an efficient and flexible way...
NGDF National Geospatial Data Framework
NSDI National and International Spatial Data Infastructures
OGDI Open Geographic/Geospatial Datastore Interface
The Open Grid Services Architecture describes an architecture for a service-oriented grid computing environment for business and scientific use, developed within the Global Grid Forum...
A spatial data infrastructure is a framework of spatial data, metadata, users and tools that are interactively connected in order to use spatial data in an efficient and flexible way...
