Transcript Geospatial Data Sharing and Interoperability - BAAMA

The Open GIS Consortium, Geospatial
Data Sharing, and Interoperability
BAAMA
April 18, 2002
Phillip C. Dibner
Ecosystem Associates
[email protected]
State of the (non-) Union
• Tens (100s?) of billions of dollars worth of spatial
data already archived at diverse sites
• Too large and expensive to move and convert
• Prohibitively inconvenient to store and manage
centrally
• Operationally constraining and administratively
challenging to mandate a single-technology supplier
The Solution: Interoperate
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Data remain in place
No constraints on maintenance operations or policy
Existing in-house tools and applications remain viable
Only the interfaces need be well-defined among
interoperating clients and servers
Open GIS
• The Open GIS Consortium (OGC) grew out of the need
among federal agencies to share data.
• Currently a collaboration of more than 230 vendors,
integrators, government and private agencies,
universities, and end users.
• Abstract Specification:
– Defines basis of discourse for standards under development
– 17 volumes.
– A living document
• 7(+) publicly available Implementation Specs published.
Many more in various stages of creation or refinement.
• Close relationship with ISO (esp. TC 211)
• Uses other standards where possible
Organization of OGC
• Planning Committee
– Steering, policy, general management and oversight
• Technical Committee (TC)
– Develops specifications, discussion papers, other technical
communications.
– Special Interest Groups (SIGs), Working Groups (WGs) that
develop specifications, and Revision WGs that revise specs.
– Consensus process.
• Interoperability Program
– Practical testbed and pilot projects
– Speeds specification development
– Helps bring products to the marketplace
A Snapshot of SIGs, WGs, and RWGs
Technology SIGs
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Architecture
Catalog
Features
Decision Support
GML
Metadata
Image Exploitation
WWW Mapping
Location Services
Information Communities
and Semantics
Domain SIGs
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Telecommunications and
Utilities
Earth Observation
Defense and Intel
Natural Resources and
Environment
Disaster Management and
Public Safety
Europe
Australia
WGs and RWGs
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Coordinate Transformation WG & RWG
Grid Coverages WG
Catalog RWG
Open Spatial Publishing and Discovery Infrastructure (OSPDI) WG
Simple Features for CORBA RWG
Simple Features Specification
• Profiled for CORBA/IDL, SQL, and OLE/COM
• Includes a Geometry interface with support for:
– Full suite of SRS and coordinate system interfaces:
• Geodetic and non-geodetic SRS
• Coordinate units
• Projection and coordinate transform interfaces
– Point, 1-D, and 2-D geometries
• Points and point strings, lines and line strings, curves, 2D surfaces, rings,
polygons, and corresponding collections
– Relational operators
• Typically boolean
• Equals, contains, touches, within, disjoint, crosses, etc.
– Set operators
• Typically geometry-valued
• Intersection, union, difference, buffer, convex hull, etc.
• Sequences of name/value pairs for non-spatial properties
• Supports Collections and Iterators
Coordinate Transformation Service
• 3 Packages: Position, Coordinate Systems, Transformations
– Enables creation of standard and customized CT objects.
– Each CT object includes a source and target Coordinate System.
– Also includes an instance of a mathematical transform class,
which performs the actual transformation of positions in the source
CS to positions in the target CS.
Geography Markup Language (GML)
• XML implementation of Simple Features and
increasingly more comprehensive set of objects.
• Rapidly becoming - or has become - the lingua franca
for the transport and storage of geographic
information.
• Specified in XML Schema
• Currently undergoing its third revision; Version 2.0
has been released.
Web Mapping Server
• Exposes its datasets through a standard CGI
interface.
• Supports heterogeneous data formats, both image
and vector, at source locations.
• May allow for querying objects within the data layers
it provides
• Returns a map image - a picture. Formats that
support transparency (GIF, PNG) allow images to be
stacked.
Web Mapping Servers and Client
Integrated View
Whoville
Whoville
Cedar Lake
Internet
Environment
Federal
Program
Social
Services
Crime
Framework
(Clearinghouse)
Weather
Adapted from Web Map Server Demonstration presentation
Land
Parcel
© 2000 OGC
NOAA Hurricane Image of the Gulf of
Mexico
Source: Web Map Service Implementation Specification
OGCProject Document 01-047r2
Political, Coastline, and Populated Areas,
Southeastern United States
Source: Web Map Service Implementation Specification
OGCProject Document 01-047r2
Combined Hurricane Image and
Population Map
Source: Web Map Service Implementation Specification
OGCProject Document 01-047r2
WMS Interface: Overview
• GetCapabilities (required): Obtain service-level metadata, which is
a machine-readable (and human-readable) description of the WMS's
information content and acceptable request parameters.
• GetMap (required): Obtain a map image whose geospatial and
dimensional parameters are well-defined.
• GetFeatureInfo (optional): Ask for information about particular
features shown on a map. A WMS or layer that supports this function is
called queryable.
WMS Interface: Operation
GetCapabilities
Web Map
Service
Capabilities XML
Document with
Layer Information
Client
GetMap
Rendered Map Image
Map Layers
Legend
Roads
Water
Buildings
Cascading Map Server
• Supports the WMS interface to client applications
• Acts like a client itself, by accessing and collating data
from a variety of servers
• Applies coordinate transforms, reprojections, and image
processing as needed
• Returns the composite image to client applications
Cascading Map Server
Map
GIF
Server WGS 84
Different viewer client in browser!
Web Browser
Capabilities
Integrator
Map
Integrator
Map
PNG
Server AL St Pln
internet
internet
Cascading Map Server
Map
GIF
Server NAD 83
JPEG
Map
Server WGS 84
Adapted from Web Map Server Demonstration presentation
© 2000 OGC
Web Feature Server (WFS)
• Passes vector data (not pictures) between server and
client
• Why? Processing of various sorts, including flexible
portrayal
• Encoding in current implementations is GML
• Basic WFS:
– GetCapabilities
– DescribeFeatureType
– GetFeature
• Transactional WFS:
– Transaction
– LockFeature
• Not yet a published standard - but maturing rapidly
Web Coverage Server (WCS)
• Coverage data, not pictures. Like WFS, but for
imagery and other coverages.
• Why? Flexible portrayal, image processing, etc.
• Supports many formats and encodings.
• Not as mature as WFS, but under intensive
development.
• Formally, a coverage is a mathematical function: a
mapping from a geographic (or temporal?) domain
space to some sort of range space, typically a
measurement or observation.
• Metadata are complex. Much active debate about
format and content of capabilities document.
Catalogs and Registries
• Element 13 of the Abstract Specification
• Stateful Catalog Interface Implementation
Specification: (doc 99-051)
– Coarse and fine-grained models for tradeoff between
detailed control and flexibility
– Defines structural as well as dynamic models
• Stateless version is in specification review process.
• Communicates with clients via Capabilities
Documents
• Next version is being actively developed and debated
– Likely based on ebRIM
– Next step towards Web Service Chaining
Sensor Web Components
© 2001 OGC, Inc. All rights reserved.
A Sensor Web Client View
© 2001 OGC, Inc. All rights reserved.
Other Specs - “In Play”
• UOM: Units of Measure. Developed with coordinate units
in mind, has general applicability.
• SLD: Styled Layer Descriptors. When combined with a
WFS, provides for a stylable WMS.
• WTS: Web Terrain Server. Renders oblique views that
incorporate elevation data.
• XIMA: XML for Image Markup and Annotation.
• CPS: Coverage Portrayal Service.
• Measurements and Observations: relevant to Sensor Web,
and to the range space of a WCS.
Current OGC Data Retrieval Operations
Sensor
Collection
Service
GetObservation
Measurement Collection
SCS
Client
Constellation of Sensors
Web
Coverage
Service
Coverage Data
Coverage Data
WCS
Client
Coverage Portrayal
Service
Web
Feature
Service
Vector Data
Map Layers
GetCoverage
GetFeature
WFS
Client
Feature Data
SLD Service
Web Map
Service
GetMap
Rendered Map Image
WMS
Client
Current Issues
• Which new specifications are the wave of the future,
which not? When to start adopting?
• Consistency among different services: consistent
schema for capabilities document, both for operation
and for discovery.
• Balancing need to innovate with producing a stable
basis for products in the marketplace.
OGC Interoperability Program
Development
Initiatives
Testbeds
Planning
Studies
OGC
Specification
Program
User Interaction
Internet
Feasibility
Studies
Infrastructure
Initiatives
Insertions
Pilots
Operators
WMSs
WFSs
WCSs
CMS
Internet
OGC Network™
© 2001 OGC, Inc. All rights reserved.
Repository
Services
External (3rd Party )
Repository Services
Interoperability
Initiative
Role of Initiatives and Working Groups
Consensus
Requirement
Working
Working
Groups
Groups
OGCNetwork
Viability
DIPRv1
Working
Working
Groups
Groups
DIPRv2
OGCNetwork
Working
Working
Groups
Groups
OGCNetwork
TC
IPR
IP Work Items
DP/Other
Development and Testing Cycles
© 2001 OGC, Inc. All rights reserved.
Practica - On the Ground with the
Interoperability Program* *
• WMT-1 and -2
– Genesis of the Web Map
Server
– Revealed need and
opportunity for GML
• Upper SusquehannaLackawanna
• Geospatial Fusion Testbed
– GeoParser, GeoCoder,
Gazetteer
– Location Organizer Folder
(LOF) spec, for an analyst to
keep track of the datasets
collected for a given project
* Complete
• CTI
• MPP-1: Military Pilot Program,
Phase 1
• OWS: Web Services Initiative (3
threads):
– 1.1: Complete
– 1.2: Kicks off May 20
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OpenLS: Location Services
CIPI: Critical Infrastructures
ODMS
MMI: Multihazard Mapping
GISD: Sustainable Development
Etc.
* Ongoing or not yet started
Example from Civil Technology Insertion
USACE MVD project sites (yellow) from ArcIMS/WMS
Oil facilities (green) and high tide line (off-white) from
LSU Geomedia/WMS, over Compusult basemap.
Cross-Agency Data Sharing
Enhanced Landsat data from NASA-JPL, overlain by a color airphoto
Mosaic hosted at CubeWerx, with a road layer from USGS and the
MVD project site information.
Resources
• OGC: www.opengis.org
– Specifications, discussion papers, news, links to product info
– Contact information
– Member pages
• OGC Network: ogcnetwork.org
• Open source products
– UMN WMS: mapserver.gis.umn.edu
– MIT Orthoserver (a WMS designed for orthophotos and imagery):
http://tull.mit.edu/orthoserver/
– GeoServer (WFS): http://geoserver.sourceforge.net