Spatial Data Infrastructure: Concepts and Components Geog 458: Map Sources and Errors March 6, 2006

What is a Spatial Data Infrastructure (SDI)? Functions –“The SDI provides a basis for spatial data discovery, evaluation, and application for users and providers within all levels of government, the commercial sector, the non-profit sector, academia and by citizens in general” Components –Denotes “base collection of technologies, policies and institutional arrangements that facilitate the availability of and access to spatial data” – GSDI Cookbook v2

Components of SDI Technology –hardware, software, networks, databases, technical implementation plans) Policies & institutional arrangements – governance, data privacy & security, data sharing, cost recovery People –training, professional development, cooperation, outreach

Why build SDI? Build data once and use it many times for many applications Integrate distributed providers of data: cooperative governance Share costs of data creation and maintenance Support sustainable economic, social, and environmental development

If SDI were developed… Improved decision –Providing decision makers what they really need: indicators, models, trends, patterns Business opportunities –Development of a private sector involved with data sales and added value Increased globalization –A chance for developing countries to participate in the knowledge economy

Here’s one overview of the pieces of the SDI

Metadata

Metadata Provides documentation of existing internal geospatial data resources within an organization (inventory) Permits structured search and comparison of held spatial data by others (catalog) Provides end-users with adequate information to take the data and use it in an appropriate context (documentation)

Three levels of metadata Discovery metadata –Provide minimum amount of information for inquirer to know the content of data Exploration metadata –Provide sufficient information to ascertain that data fit for a given purpose exists Exploitation metadata –Includes properties required to access, transfer, load, interpret, and apply the data in the end application where it is exploited

Metadata should be used to describe all types of data, emphasis on ‘truth in labeling’ Metadata Geospatial data

Special-use thematic layers are built and described as available geospatial data Common data layers are being defined in the Framework activity Metadata GEOdata Framework

Framework supports Community development of sets of spatial features, feature representation, and attribution to a lowest common denominator Participant collecting, converting, or associating information to common Framework feature specifications Multiple representations of real-world features at different scales and times by feature identifier and generalization

SDI include services to help discover and interact with data Metadata GEOdata Services Framework

An important common service in SDI is that of discovering resources through metadata Metadata GEOdata Framework Services Discovery Access Processing The Discovery Service is the core function of the clearinghouse for geospatial information

Clearinghouse provides Search for spatial data through fields and full- text in the metadata Links through to full data access, where available Supports uniform, distributed search through a single user interface to all servers worldwide A fee advertising mechanism to provide world access to your holdings under the principles of “truth-in-labeling”

A second class of services provides standardized access to geospatial information Metadata GEOdata Framework Services Discovery Access Processing This may be made via static files on ftp or via online data streaming services. These services deliver ‘raw’ data, not maps

Data Access Concepts Standardization of data access implies several things: –Definition of model used for the data to be exchanged –Adoption of an exchange or encoding format –Agreement on data access protocol(s) Organization should strive to identify the mode(s) of operation to simplify data exchange

Data Access Examples Administrative boundary data conforming to the GlobalMap data model, packaged as Vector Product Format (VPF), made accessible over ftp Panchromatic 10m, single-band, rectified imagery to a specific coordinate reference system, packaged as GEOTIFF with LZW compression, made accessible on CD- ROM

A third class of services provides additional processing on geospatial information Metadata GEOdata Framework Discovery Access Processing Services

Processing Services These include capabilities that extend and enhance the delivery of data through processes applied to raw data: –Web mapping services –Symbolization –Coordinate transformation –Analysis or topologic overlay services

Standardization makes SDI work Standardizations touch every SDI activity Metadata GEOdata Service Framework Standards Standards include specifications (OGC), formal standards (ISO), and documented practices

SDI is built upon partnerships Partnerships Metadata GEOdata Service Framework Standards

Roles of standards bodies OGC ISO TC 211 National Standards NSDI Software interfaces (Implementation Specifications) Foundations for implementation (Abstract standards) Content standards, Authority for data Other NSDI Endorsed practices and specifications

Developing SDI Developing core data –Standards for framework or reference data Describing data: metadata –Metadata content standards (e.g. CSDGM) Discovering data: data catalogue –Standards for data clearinghouse (e.g. Z39.50) Accessing data: data access –Data exchange/format standards (e.g. SDTS) Processing data: data portrayal and processing –Web mapping, geoprocessing service (e.g. W3C)