Agi08 Jeremy Morley
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The document discusses the roles of Google and the Open Geospatial Consortium (OGC) in geospatial information systems and web mapping. It provides an overview of Google's geospatial technologies like Google Maps, Google Earth, and KML. It then introduces the OGC, its standards including GML and Web Map Service (WMS), and how these standards enable interoperability between different systems. The document argues that while Google is useful for many applications, the OGC is still needed for applications involving custom basemaps, connecting desktop GIS to web services, mixing data from different sources, or creating complex geospatial models.
![O tliOutline
• [ Web mapping under the hood ]
G l ' ti l t• Google's geospatial systems
• Introduction to the OGCIntroduction to the OGC
• Google Maps versus OGC Web Map
Services
B d b i• Beyond web mapping](https://image.slidesharecdn.com/agi08jeremymorley1-1224506263484354-9/85/Agi08-Jeremy-Morley-3-320.jpg)
Agi08 Jeremy Morley
- 1. If we have Google, do weIf we have Google, do wegg need the OGC?need the OGC? J M lJeremy Morley [email protected] y@ g Dept. Civil, Environmental & GeomaticDept. Civil, Environmental & Geomatic Engineering, UCL
- 2. G lGoal • To explore the places of Google and the Open Geospatial Consortium (OGC) inOpen Geospatial Consortium (OGC) in geospatial information systems, especially web mapping (And by extension Microsoft Virtual Earth• (And by extension, Microsoft Virtual Earth, Multimap, OS OpenSpace, etc.)p p p )
- 3. O tliOutline • [ Web mapping under the hood ] G l ' ti l t• Google's geospatial systems • Introduction to the OGCIntroduction to the OGC • Google Maps versus OGC Web Map Services B d b i• Beyond web mapping
- 4. G l ' ti l tGoogle's geospatial systems • Google Maps G l E th• Google Earth • KMLKML • SketchUp – 3D design sketching software Recent addition: ArcGIS connector– Recent addition: ArcGIS connector – Collada (XML 3D exchange format)( g )
- 5. Google Maps
- 6. Particular features of Google MapsParticular features of Google Maps • AJAX programming => interactivityAJAX programming > interactivity • Good UI (simple, uncluttered) • Data! Fi d l l i• Fixed zoom levels, raster mapping (<=> server farms cartography)(< > server farms, cartography) • Well integrated functionality, – e.g. route planning with vector overlay Published public free (to some) access• Published, public, free (to some) access, Javascript API
- 7. Public API -> Mashups Wikimapia www.wikimapia.org Public API Mashups
- 10. Scientific data in Google EarthScientific data in Google Earth The Visual Exploration of Insurance Data in Google Earthp g Aidan Slingsby, Jason Dykes, Jo Wood, Matthew Foote, Mike Blom Proceedings of GISRUK 2008
- 11. KML Now an OGC standard KML • Used by Google to describe geographic features & services, particularly for Google Maps & Earth, p y g p • An XML application to: – Specify icons and labels to identify locations on the planet surface – Create different camera positions to define unique views for each of your features – Use image overlays attached to the ground or screenUse image overlays attached to the ground or screen – Define styles to specify feature appearance – Write HTML descriptions of features, including hyperlinks and embedded imagesembedded images – Use folders for hierarchical grouping of features – Dynamically fetch and update KML files from remote or local network locations – Fetch KML data based on changes in the 3D viewer – Display COLLADA textured 3D objects (SketchUp)Display COLLADA textured 3D objects (SketchUp) • http://earth.google.com/kml/whatiskml.html
- 12. Introduction to the OGCIntroduction to the OGC • Open Geospatial ConsortiumOpen Geospatial Consortium • Consortium of vendors, users, academics involved fin geospatial information technologies • Includes the major GIS vendors, the largestIncludes the major GIS vendors, the largest players in the IT world, small companies, national agencies universitiesagencies, universities – E.g. Mapinfo, ESRI, Intergraph, Cadcorp,.. Google Microsoft Oracle– Google, Microsoft, Oracle – NASA, ESA, USGS, OS, BGS, NERC – UCL Nottingham EDINA City University– UCL, Nottingham, EDINA, City University
- 13. OGC Obj tiOGC Objectives • Promote the use of “interoperable geoprocessing” throughout the Information Technology marketplacethroughout the Information Technology marketplace. • Synchronize “geoprocessing technology” with commercial “Information Technology standards”Information Technology standards • Arrange cooperation of “GI product suppliers” and “GI ” t d l i t bl ft i t fusers” to develop interoperable software interfaces • Involve the entire community in the “interoperability ”process” • Provide an “industry forum” for “partnerships” and cooperative business development projects.
- 14. S h t h th OGC i ?So, what has the OGC given us? • GML for geographic data exchange • Standardised methods for interacting with GIS web servicesGIS web services – NB: care over the phrase "web services" • Wide range of GIS web services: Web Map Service– Web Map Service – Web Coverage & Feature Services – Catalog Service for the Web
- 15. GML – Geographic Markup Language • GML is one of the older standards • Concerned with data, not representation (cf KML)(cf. KML) • Has evolved with time to add functionality • GML 2: – XML for Simple FeaturesXML for Simple Features – "Simple features" 2D vector data only + feature collectionscollections – Version 2.1.2 used as foundation for OS Mastermap
- 16. GML 3GML 3 • In addition to simple 2D linear features: features with complex, non-linear, 3D geometry; featuresg y with 2D topology, features with temporal properties, dynamic features, coverages, and observations; • represent spatial and temporal reference systems, units of measure and standards information; • use reference system, units and standards information in the representation of geospatial phenomena,p g p p , observations, and values; • represent default styles for feature and coveragerepresent default styles for feature and coverage visualization.
- 17. OGC W b M iOGC Web Mapping Th diff t i f i t t• Three different services of interest: – Web Map Service (WMS), Web Feature Service (WFS), Web Coverage Service (WCS) • Server-side mapping methodsServer side mapping methods • Map (and other) requests are made through standard HTTP methodsstandard HTTP methods – URL – Parameters supplied within URL (GET) or hidden in document (POST) – One request gives one response (stateless)
- 18. Example – UCL's ICEDSUCL s ICEDS Partially transparent GOES imagery overlaid on SRTM topography – iceds.ge.ucl.ac.uk
- 19. Cascaded services • ICEDS can act as client as well as server • Requests for non-local layers are passed through to other services on the webthrough to other services on the web • This is known as cascadingThis is known as cascading WMS UCL ICEDSWEB BROWSER UCL ICEDS Acting as proxy: cascade requests, assemble map WEB BROWSER ICEDS portal Web requests, assemble map OGC server ICEDS portal Web site OGC Services, e g CIESIN WMS OGC server Geospatial (DHTML + Javascript) WMS e.g. CIESIN WFS/ WCS Geospatial data storage p )
- 20. Wh OGC?Why OGC? • Standardised access to data and map servicesservices • Independence from vendor/database/OSp => choice, flexibility, upgrade, 'free' prototyping • Clients can start to access different providers' services with minimal extraproviders services with minimal extra programming
- 21. Best of breed,, software independence These are the OGC t d d l UCL ICEDS These are the components we use. Chosen best of breed OGC standards also give independence from spatial Acting as proxy: cascade requests, assemble map Chosen best of breed open source elements BUT could easily from spatial database / file systems in ti d t & Stores case annotations Mapserver substitute different components, e.g. vendor solutions presenting data & catalogue to the Internet Geoserver Files vendor solutions Internet PostGIS
- 22. Google Maps versus OGC WMSg p 1 - Interfaces • GUI WMS t i i d d t f GUI– WMS, etc., is independent of GUI – Open source interfaces are available to buildp upon, e.g. OpenLayers, similar to Google Maps ArcGIS Explorer NASA WorldWind globes– ArcGIS Explorer, NASA WorldWind globes • Programming: what's in an API?g g – The Google API has clearly encouraged uptake Si il API il bl f th i l &– Similar APIs available for other commercial & open source clients, e.g. OpenLayers, ESRI
- 23. Google Maps versus OGC WMSg p 2 - Data • The principle advantage of Google (or Microsoft OS Multimap etc )Microsoft, OS, Multimap etc.) • However a number of cascadable, open, p access global data WMS O St t– OpenStreetmap – JPL's OnEarth global satellite mapsg p – UCL ICEDS for terrain b t 'll h t f & h t d t t t– but you'll have to pay for & host data to get same resolution as Google (etc)
- 24. Google Maps versus OGC WMSg p - Mixed mode • Possible to mix Google Maps data layers with OGC WMSwith OGC WMS – Still needs a Google Maps API key http://www openlayers org/dhttp://www.openlayers.org/d ev/examples/example- list.html
- 25. OGC i h t i tiOGC service characteristics "Complex"• "Complex" – Needn't be more complex to set up than vendor web- GIS solutions – Possibly, if using separate client and server components, but standardised interfaces – Issues of security, authentication, availability in cross-y y institution systems. Fair comparison? • "Slow"Slow – If unconstrained client, server will have to work to generate maps Difficult to cachegenerate maps. Difficult to cache. – So constrain zoom, using cached tiles (Ka-Map)
- 26. W b d tWeb data access • We can move beyond simple Web client access to map imagesaccess to map images • Most GIS vendors are OGC members • Therefore most support connection to OGCOGC services – WMS common and relatively matureWMS common and relatively mature
- 27. WMS Connection from ArcGISWMS Connection from ArcGIS ArcGIS 8.3…
- 28. W b d t (2)Web data access (2) • What if we want to access source data? W b C S i (WCS)• Web Coverage Service (WCS) – raster/coveragesg • Web Feature Service (WFS) – /fvector/features
- 29. Cadcorp – WMS & WFSp
- 30. Comsine Ltd.: WCS demonstrationWCS demonstration wcs_url = 'http://iceds.ge.ucl.ac.uk/cgi- bin/wcs?map=wcs map&SERVICE=WCS&REQUEST=GetCoverbin/wcs?map=wcs.map&SERVICE=WCS&REQUEST=GetCover age&COVERAGE=srtm&FORMAT=GEOTIFFINT16' res = max(tif_pixsize_x, tif_pixsize_y) wcsRequest = wcs_url + "&CRS=EPSG:" + str(epsg) + "&BBOX=" + bbox + "&RESX=" + str(res) + "&RESY=" + str(res) logger.info("WCS REQUEST " + wcsRequest) if (dem == None):if (dem == None): demFilename = str(time.clock()) + ".tif" urllib.urlretrieve(wcsRequest, filename) cleanup = 1
- 31. Beyond Web MappingBeyond Web Mapping • Web processingp g • Service chaining • Sensor webs• Sensor webs – http://www.opengeospatial.org/projects/groups/sensorweb – http://vast.uah.edu/SensorML • City & building modelling (CityGML)y g g ( y ) • ISO TC/211: geospatial standards
- 32. GEOSSGEOSS • Global Earth Observation System of Systems (http://www earthobservations org/)(http://www.earthobservations.org/) • An attempt to create an umbrella systemp y giving access to data from national & international remote sensing space agenciesinternational remote sensing space agencies • Hence distributed data, and probablyHence distributed data, and probably distributed processing • Each agency maintains own services
- 34. ConclusionsConclusions • If we have Google do we need the OGC?• If we have Google, do we need the OGC? • Yes and no – depends on your applicationp y pp • Probably not for mass-market / consumer ( )web mapping (but, mixed system mash-ups) • But yes if you want to:• But yes if you want to: – use own base maps, or complex overlays; – connect desktop GIS to GIS web services; start mixing data from different services; or– start mixing data from different services; or – create complex geospatial models or services.
- 35. W b P iWeb Processing • In future we will want to do more than just display data off the webdisplay data off the web • What if we want to insert some processingp g (from rendering through to data analysis)? And do this in flexible on the flyAnd do this in flexible, on-the-fly architectures? • Web Processing Services (WPS) R t ti l d l ti l– Runs geocomputational models or geospatial operations on user-supplied datasets
- 36. S i h i iService chaining How do we compose a sequence of• How do we compose a sequence of processes, a service chain?p • Adopt technology from the IT industry: • BPEL: Business Processes Execution LanguageLanguage • Increasingly important for distributed data & distributed processing This is just part of the interoperable• This is just part of the interoperable infrastructure needed
- 37. Fine dust (PM10) prediction maps Discover Log in Access Order SSE Portal Order Discover Service Request access Results View SOS/WMS BPEL Workflow Web Service at IRCEL Web Service at Vito OVL Forecast Model RIO Interpolation Model SOS PM10 WMS PM10 Maps WCS/WMS AOD SOS Forecasts Model Model Maps Slide from Yves Coen, GEOSS ADC Architecture W k h 2/2008 AOD ToolkitPM10 measurements OVL Forecasts Workshop, 2/2008
- 38. Fine Dust Forecast - Result Slides from Yves Coen, GEOSS ADC Architecture Workshop, 2/2008
- 39. W b i d th b tWeb mapping – under the bonnet • Web mapping is a client/server system Cli t PC d it b b• Client: your PC and its web browser • Server: the web servers (hardware andServer: the web servers (hardware and software) Th t d i f b i d i• The art and science of web mapping design is especially about the balance betweenp y client and server processing
- 40. Simple server-side mapsp p Client Server 1. Browser requests map URL 4. Map tiles are requested to build Web page 2. Web server calls Internet map script via CGI 3 S i t Browser software Web server 3. Script returns HTML doc referring to Files / Map script - returns custom HTML document specific map tile images Files / D'base Example: Streetmap.co.uk
- 41. Server-side interactive mappingpp g Client Server 2 1 2 3 Web server 5 Internet Web server Servlet Exec Browser software Internet Map Web page script 4 Fil / Map Server Files / D'base Example: USGS Coastal Mapping (ArcIMS)
- 42. Client/server systemy Client Server 1 2 5 3 4 Web server 6 Internet Browser software Web server Servlet Exec Internet Map Web page script Browser Files / Map ServerJava GIS app. Browser plug-in Files / D'base Java VM Example: Flash Earth