Introduction to WEB-GIS - ESCAP

1 Introduction to Introduction to WEBWEB--GISGISC hathura H WickramasingheChathura H Wickramasinghe MappingMapping is inventory and presentation of is inventory and presentation of spatial data. GIS means GIS means Geographical information Geographical information SystemSystem Its called that because there is information Its called that because there is information behind the the information SystemsGeographic information SystemsGIC/AIT chathura Difference between mapping software or CAD and GIS:Difference between mapping software or CAD and GIS:CAD CAD Mapping 2D or 3D geospatial dataMapping 2D or 3D geospatial dataGISGIS Three levels of GIS applications:Three levels of GIS applications: Inventory (What is there?)Inventory (What is there?) Analysis (Answering questions)Analysis (Answering questions) Shortest distance Shortest distance Modeling (Making predictions)Modeling (Making predictions)GIS vs CAD GIS vs CAD CAD stands for Computer-Aided DesignGIC/AIT chathura Image: ESRI course Learning ArcGIS Desktop 2007A GIS is a software system that connects map layers with tables of information .

2 GIC/AIT chathura GIS MAP GIS is different than most applicationsGIS is different than most applications Word processing, SpreadsheetsWord processing, are entirely dependent on input of entirely dependent on input of YOUR YOUR datadata GIS users nearly always require reference GIS users nearly always require reference map data ( , streets, boundaries) that are map data ( , streets, boundaries) that are maintained maintained by othersby others As GIS users, we rely heavily on As GIS users, we rely heavily on externalexternal data sourcesdata sourcesImportance of geographic DataImportance of geographic DataGIC/AIT chathura Data has to be shared Evolution of Data SharingEvolution of Data SharingTimeSharedSharedDiskspaceDiskspac eMaturityMedia Media DistributionDistribution(( ftpftp ))DownloadingDownloadingDataDataDistribu ted GISD istributed GIS(via web services)(via web services) Getting all the data Getting all the data VintageVintage FormatFormat Coordinate system /ProjectionCoordinate system /Projection Media CompatibilityMedia Compatibility File SizeFile Size BandwidthBandwidth Metadata DistributionMetadata DistributionIssues with typical/traditional Data Issues with typical/traditional Data Sharing MethodsSharing MethodsTypically requires data manipulation prior to use (reformatting, reprojecting, clipping, etc.)

3 GIC/AIT chathura Distributed GIS ModelDistributed GIS ModelUSGSNYS CSCICNYS DECUS EPAV irtually Any ClientDEMW etlandsOrthosReal-time access to geographic data and servicesLocal Data An application that combines data from multiple sourcesAn application that combines data from multiple sources Referred to as Referred to as content aggregationcontent aggregation Combines Combines similarsimilartypes of data ( , maps,) from types of data ( , maps,) from differentdifferentsystems/servicessystem s/services Term originated from music industry when a new song Term originated from music industry when a new song was made from several existing trackswas made from several existing tracksMashupMashup+= Format is irrelevantFormat is irrelevant Guarantees latest dataGuarantees latest data No media involved No media involved Size is irrelevant (only requested Size is irrelevant (only requested data needed)data needed) Software independent Software independent Distributed GIS AdvantagesDistributed GIS AdvantagesGIC/AIT chathura Distributed GIS AdvantagesDistributed GIS Advantages Device independent (PC, phone) Device independent (PC, phone) Saves Time!

4 Saves Time! Data security Data security Only view dataOnly view data Download dataDownload data Data upload and editing Data upload and editing Desktop software's also support WMSD esktop software's also support WMS QGISQGIS ArcGISArcGIS AdvantagesAdvantages Carryout advance GIS operations on the advance GIS operations on the data. Use as source data for GIS as source data for GIS analysis. Easy to search and access to search and access GIS AdvantagesDistributed GIS Advantages Dependent on server availability Dependent on server availability Dependent on internet availabilityDependent on internet availability Users need to be aware of web service Users need to be aware of web service Distributed GIS DisadvantagesDistributed GIS DisadvantagesGIC/AIT chathura Architecture that is based on integrating Architecture that is based on integrating loosely coupledloosely coupled , interoperable services.

5 Interoperable services Loosely coupled means NOT physically Loosely coupled means NOT physically bound or compiled like an EXE or DLLbound or compiled like an EXE or DLL These services can be invoked and These services can be invoked and consumed remotely over a networkconsumed remotely over a network Data and messages are exchanged Data and messages are exchanged between clients and servicesbetween clients and servicesService Oriented Service Oriented ArchitectureArchitectureGIC/AIT chathura Basic Web Page OperationBasic Web Page OperationRequestResponse(HTML document)GIC/AIT chathura Web Service OperationWeb Service OperationWeb Server(Listening for requests)1. Creates XML Request2. Request sent to web service 3. Receives request and parses XML4. Calls the function5. Creates response XML with results6. Response sent to client7.

6 Receives response and parsesClientZone: 18 Easting: 623, : 4,745, UTM To : : chathura Map/Data Oriented ServicesMap/Data Oriented Services Map Services (Image)Map Services (Image) Feature Services (Vector)Feature Services (Vector) Coverage Services (Grid)Coverage Services (Grid) Task Oriented ServicesTask Oriented Services Routing ServicesRouting Services Geoprocessing ServicesGeoprocessing ServicesTypes of Geospatial Web ServicesTypes of Geospatial Web ServicesGIC/AIT chathura Client requests a map from a server for a specified geographic eClient requests a map from a server for a specified geographic extentxtent Map Server renders the requested map internally and converts to Map Server renders the requested map internally and converts to an an image file ( , JPG, PNG, GIF) and returns the map image to thimage file ( , JPG, PNG, GIF)

7 And returns the map image to the e client for displayclient for display Fast map display is map display is possible. Google MapGoogle Map made way for WebGIS popularity made way for WebGIS popularity Map ServicesMap ServicesGIC/AIT chathura 99% of current activity's in Web GIS Map/Image ServingMap Service OperationMap Service OperationWeb Server/Map ServerClient5. Map Server generates map as image file1. Creates XML Request2. Request sent to web service 3. Receives request and parses XML4. Calls the map server to request map6. Creates response XML with image file7. Response sent to client8. Receives response, parses to extract image and updates map siteSample siteGIC/AIT chathura Every one was creating own standardsEvery one was creating own standards Google mapsGoogle maps Bing MapsBing Maps USGS USGS Make universal data sharing universal data sharing possible.

8 Overcome technical technical chalengers. Make way for rapid development in Make way for rapid development in for standardizationNeed for standardization The The Open Geospatial Consortium (OGC)Open Geospatial Consortium (OGC)was founded in 1994was founded in 1994 An international consortium of 346 organizations that lead the An international consortium of 346 organizations that lead the development of open standards and specifications to enable the development of open standards and specifications to enable the interoperability of geospatial and location based servicesinteroperability of geospatial and location based services They have developed a series of open standards for geospatial weThey have developed a series of open standards for geospatial web b services such as:services such as: Geography Markup Language (GML)Geography Markup Language (GML) Web Mapping Services (WMS)Web Mapping Services (WMS) Web Feature Services (WFS)Web Feature Services (WFS) Web Coverage Services (WCS)Web Coverage Services (WCS) Referrred to as Referrred to as OpenGISOpenGIS standardsstandardsOGC and Open Web MappingOGC and Open Web MappingOGC Web Services (OWS)OGC Web Services (OWS) Web Map Service (WMS)Web Map Service (WMS) W eb Map Service Interface Standard (W MS) provides a simple HTTP W eb Map Service Interface Standard (W MS) provides a simple HTTP interface for interface for requesting georequesting geo--registered map images from one or more distributed geospatial registered map images from one or more distributed geospatial databases.

9 A W MS request defines the geographic layer(s) and aredatabases. A W MS request defines the geographic layer(s) and area of interest to a of interest to be processed. The response to the request is one or more geobe processed. The response to the request is one or more geo--registered map registered map images (returned as JPEG, PNG, etc) that can be displayed in a bimages (returned as JPEG, PNG, etc) that can be displayed in a browser rowser Web Feature Service (WFS)Web Feature Service (WFS) The W FS operations support INSERT, UPDATE, DELETE, LOCK, QUERY aThe W FS operations support INSERT, UPDATE, DELETE, LOCK, QUERY and nd DISCOVERY operations on geographic features using HTTP as the diDISCOVERY operations on geographic features using HTTP as the distributed stributed computing platform.

10 It is the function of a web feature service,computing platform. It is the function of a web feature service,in its interaction with in its interaction with the data storage system used to persistently store features, to the data storage system used to persistently store features, to ensure that changes ensure that changes to data are consistent. to data are consistent. Web Coverage Service (WCS)Web Coverage Service (WCS) The OpenGISThe OpenGIS W eb Coverage Service Interface Standard (WCS) defines a W eb Coverage Service Interface Standard (WCS) defines a standard interface and operations that enables interoperable accstandard interface and operations that enables interoperable access to geospatial ess to geospatial "coverages" [ ]. The "coverages" [ ].