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

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

Sep 04, 2023 347 likes •582 views

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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SLIDE 5

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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SLIDE 7

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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SLIDE 8

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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SLIDE 17

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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SLIDE 18

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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SLIDE 19

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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SLIDE 22

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