GIS data standards

• The objective of data standards is to ensure data can be understood and used consistently by different users
• Data standards


  Provide definition for data structure, data content, and rules to increase mutual understanding, eliminate technical problems in data exchange, and increase data integration and interoperability
• Levels of data standardization

  • Generic standardization (syntax, data description)
  • GIS application-independent standardization (geometry, topology, quality, metadata)
  • GIS application-specific standardization (for specific applications like cadastre, utilities, urban planning)
• The Open Geospatial Consortium (OGC) was established in 1994 to develop open solutions for geographic information processing
• Elements of OGC standardization

  • Conceptual modeling and application schema
  • Data transfer formats
  • Data encoding
  • Spatial representation
  • Spatial referencing
  • Temporal characteristics
  • Data quality description and evaluation
  • Visualization and portrayal
  • Geographic information services and interfaces
  • Object catalogues and metadata
• Conceptual modeling


  Abstract representation of real-world features, using formal conceptual schemas to describe the universe of discourse
• Object-oriented modeling


  Each data element is considered an object in the standardization work
• Conceptual schema language


  Unified Modeling Language (UML) is commonly used to develop conceptual schemas and templates
• Standard transfer formats


  Include attribute, spatial, and metadata files, as well as rules for geometry transfer, linking geometry and attributes, and metadata transfer
• Standard transfer format files should include rules defining how the data is to be transferred
• Different files contribute together to form a single file
• Standard transfer format files should include rules
• Rules


  Define how the geometry is transferred
• Transfer of links


  Between the geometry and attribute data
• Attribute data transfer


  How it is done
• Transfer of metadata


  How the metadata is transferred
• Encoding


  Rules allow geographic information to be coded into a system of independent data structure suitable for transport or storage
• Components of encoded data

  • Head
  • Index
  • Data dictionary
  • Data elements
• Spatial representation


  Vector data model or raster data model
• Spatial referencing


  Datum, anchor point, prime meridian, coordinate system with units, direction, sequence of axes
• Temporal characteristics


  Use of ISO 8601 calendar and 24 hour coordinate universal time
• Elements of data quality statements

  • Positional accuracy
  • Attribute accuracy
  • Temporal accuracy
  • Completeness
• Visualization/Portrayal


  Use of computer graphic standards like OpenGL, GKS to visualize geometry
• Geographic Information Services and Interface standards

  Allow users to access and process geographic data from variety of sources across computing interfaces
• Themes for application level standardization

  • Buildings
  • Transport
  • Utilities
  • Land use
  • Administrative units
  • Water
• Metadata


  Data about data, describing who, what, where, when, how of the data
• Metadata attributes


  • Data set identification
  • Constraints
  • Data quality
  • Content information
  • Portrayal catalog
  • Distribution
  • Extension information
  • Extent
  • Citation
  • Responsible party