Interoperability in Geospatial Web Services Jeff de La Beaujardire, - - PowerPoint PPT Presentation

interoperability in geospatial web services
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Interoperability in Geospatial Web Services Jeff de La Beaujardire, - - PowerPoint PPT Presentation

Geospatial Interoperability Office Interoperability in Geospatial Web Services Jeff de La Beaujardire, PhD NASA Geospatial Interoperability Office Editor, WMS 1.1 Specification jeff2002@sunrise.gsfc.nasa.gov +1 301-286-1569 Geospatial


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SLIDE 1

Geospatial Interoperability Office

Interoperability in Geospatial Web Services

Jeff de La Beaujardière, PhD NASA Geospatial Interoperability Office

Editor, WMS 1.1 Specification jeff2002@sunrise.gsfc.nasa.gov +1 301-286-1569

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SLIDE 2

Geospatial Interoperability Office

The Problem

  • Most existing internet map & data servers are

not "interoperable" – each has vendor-specific access method – access often requires human operator – service metadata is not standardized Mapquest Xerox PARC Topozone NASA Archive User

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SLIDE 3

Geospatial Interoperability Office

The Solution

  • Standardized protocols for requesting

geospatial information & services via HTTP

  • Well-defined schema for service metadata

User

GLOBE USGS Natl Atlas Microsoft Terraservice CubeWerx Canada

Interfaces

  • Open standard
  • Vendor-neutral
  • Georeferenced
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SLIDE 4

Geospatial Interoperability Office

Open GIS Consortium (OGC)

GIS = Geographic Information System

  • OGC Members:

– 220+ institutions worldwide – software vendors, government, universities

  • Consensus development of open standards

for interoperability

  • Current focus on geospatial web services

– Building on HTTP, XML, etc – Experimenting with WSDL, SOAP, UDDI www.opengis.org

WSDL = Web Services Description Language SOAP = Simple Object Access Protocol UDDI = Universal Description & Discovery Interface

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Geospatial Interoperability Office

OGC Testbeds

  • Sponsorship by government agencies

(or corporations)

  • Cost sharing funds to vendors & academia
  • Collaborative development of specifications
  • Iterative prototyping
  • Proven interoperability through working

software

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SLIDE 6

Geospatial Interoperability Office

Web Map Service

  • WMS 1.0: 2000-04, WMS 1.1.1: 2002-04
  • Scope: geographic data rendered as an image

(a "map"), not actual data values

  • Operations:

– GetCapabilities - send service metadata – GetMap - produce map of desired area – GetFeatureInfo (opt.) - describe feature at point

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Geospatial Interoperability Office

Standardized Service Metadata

  • Each OGC Web Service (OWS) is self-

describing

  • GetCapabilities operation - predefined URL

syntax to request service description

  • Response is "Capabilities XML" document

(XML = Extensible Markup Language)

  • Standard format & vocabulary

– automatically parsed by Clients – harvested by Catalogs – legible to humans if necessary

semantic interoperability

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Geospatial Interoperability Office

WMS Metadata

  • Title of server and general information
  • Base URL for each operation
  • List of map layers available
  • For each map layer, possible metadata include:

– Name, Title, Abstract, Keywords – Coordinate systems & bounding boxes – Available rendering styles – Dimensional parameters (e.g., time) – URL of dataset metadata (FGDC/ISO 19115)

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Geospatial Interoperability Office

Standardized Request Messages

  • HTTP GET: parameters appended to base URL

– SERVICE=WMS&REQUEST=GetCapabilities – SERVICE=WMS&REQUEST=GetMap& LAYERS=layers& STYLES=styles& FORMAT=format& SRS=coordinate_system& BBOX=bounding_box& WIDTH=width& HEIGHT=height

⇒ Map "Client" can simply be a web page!

  • HTTP POST: Request is encoded as XML

document

map size & location technical interoperability

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Geospatial Interoperability Office

Viewer Client: Combined Map Server 1 Server 2 Server 3 Server 1: Topography Server 2: Water Server 3: Boundaries

Catalog Service GetMap Interoperable Web Mapping

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Geospatial Interoperability Office

Broader Adoption of WMS

  • ISO 19128 Committee Draft issued 2002-09

– Vote for adoption as Draft Intl Std 2002-12

  • Commercial vendor products
  • Growing number of servers world-wide
  • Core standard of GeoConnections Canada
  • Core standard of US Geospatial One-Stop
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SLIDE 12

Geospatial Interoperability Office

viewer.digitalearth.gov

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Geospatial Interoperability Office

WMS Context XML

  • Draft v0.1.4 released 2002-08
  • Scope: Description of a composite map

(from multiple WMS servers) – save state of Client application – reproduce view in another Client

  • XML document enumerating:

– map(s) provided by each WMS – overall bounding box – other useful info

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SLIDE 14

Geospatial Interoperability Office

Web Feature Service (WFS)

– Transaction (optional) – LockFeature (optional)

  • WFS 1.0: 2002-09
  • Scope: storage & retrieval of geographic

vector feature data (point/line/polygon)

  • XML data encoding format:

Geography Markup Language (GML)

  • Filter Specification: Restrict WFS
  • utput based on user criteria
  • Operations:

– GetCapabilities – DescribeFeatureType – GetFeature

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SLIDE 15

Geospatial Interoperability Office

Web Coverage Service (WCS)

  • Draft v0.7 released 2002-04
  • Scope: Retrieval of gridded, swath, TIN or
  • ther "coverage" data in binary or other

formats (HDF, GeoTIFF, NITF, NetCDF, etc.)

  • Operations:

– GetCapabilities – GetCoverage

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Geospatial Interoperability Office

Portrayal Services

  • Client submits GetMap request to portrayal service
  • "Enhanced" request includes:

– URL of 3rd-party WFS or WCS from which to get data – URL of Styled Layer Descriptor (SLD) document describing how data are to be represented

  • Response is map image for display by simple client

(e.g., web browser)

Portrayal Service WFS Client GetMap Image GetFeature GML

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Geospatial Interoperability Office

Web Terrain Service

  • Draft v0.3.2 released 2001-08
  • Scope: Perspective views of terrain,

possibly with additional data overlaid

  • A generalization of Web Map Service to

views that are not "straight down"

  • Operations:

– GetCapabilities – GetView

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Geospatial Interoperability Office

Gazetteer

  • Draft v0.9 issued 2002-09
  • A specialization of WFS
  • Scope: Given a place name (or other

identifier), return geometry and attributes as a GML Feature ⇒ User can navigate by place name rather than by coordinates

Gazetteer Client Montreal? longitude -73.58°, latitude 45.50°

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Geospatial Interoperability Office

Web Registry Service

  • Draft v0.0.2 issued 2001-01

– "Stateless" HTTP version of session-

  • riented Catalog Service v1.0 (1999)
  • Scope: Searchable catalog of services and

data

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Geospatial Interoperability Office

Other Planets!

  • Nothing fundamentally "geo" about these

geospatial services – except variable coordinate reference system ID

Mars WMS by CubeWerx (Canada)

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Geospatial Interoperability Office

Web Browser (Thin Client) @ users GIS Software, DSS (Thick Client) @ portal host site

Geospatial One-Stop Portal

Geospatial Web Services Gazetteer Registry Clients WMS WFS WCS Legend:

@ provider

  • rganizations

Framework Data

Geospatial One-Stop Portal

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Geospatial Interoperability Office

Web Browser (Thin Client) @ users GIS Software, DSS (Thick Client) @ portal host site

Geospatial One-Stop Portal

Geospatial Web Services Gazetteer Registry Clients WMS WFS WCS Legend:

@ provider

  • rganizations

Framework Data

Geospatial One-Stop Portal

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SLIDE 23

Geospatial Interoperability Office

WMS Data

WMS Context Map 3 Map 2 Map 1

WFS metadata Feature Data (GML) WCS metadata Coverage Data metadata Portrayal Service Registry Gazetteer

Summary

Client