GIS Data Accuracy and Accessibility

Importance of Accurate Spatial Data

• Accurate and comprehensive spatial data is critical for reliable maps.
• Inaccurate data can lead to inefficient mapping.

Advances in Data Accessibility

• Historically, GIS practitioners relied on physical maps from libraries or government.
• These maps needed manual digitization for GIS use.
• Today, online GIS resources offer ready-to-use datasets.

Key Takeaway

• Before creating data, verify if a reputable source already holds the data.
• Using existing resources saves time and ensures accurate and up-to-date data.

Sources of Spatial Data

• Spatial data comes from state, local, and federal agencies.
• Many agencies maintain GIS clearinghouses.

State and Local GIS Data Clearinghouses

• State, local governments, and nonprofits often have GIS data repositories.
• Oklahoma examples:
  • Oklahoma Water Resources Board (groundwater/surface water data)
  • Oklahoma Geographic Information Council (digital ortho-photography)
  • Association of Central Oklahoma Governments (local transportation data)
  • City of Norman (planning, zoning, and oil/gas data)

Federal GIS Data Clearinghouses

• Federal agencies manage data essential to infrastructure, environmental protection, and national security.
• Examples and their datasets include:
  • National Geospatial-Intelligence Agency (NGA) (global place names)
  • U.S. Fish and Wildlife Service (species distribution/critical habitat)
  • U.S. Environmental Protection Agency (EPA) (environmental data)

Key Federal Data Sources (USGS)

• Produces vector and raster data for natural feature mapping.
• Common datasets:
  • Digital Elevation Models (DEMs) (elevation)
  • Digital Ortho Photo Quads (DOQs) (corrected aerial imagery)
  • National Hydrography Dataset (NHD) (rivers/streams).

US Census Bureau (TIGER Data)

• Manages topographic and demographic GIS data through TIGER (Topologically Integrated Geographic Encoding and Referencing) products.
• TIGER includes:
  • Census geographies (block groups, census tracts, counties, etc.)
  • Roadways, railways, hydrography.
• FIPS Codes:
  • Unique identifiers for census geographies.
  • Hierarchically structured to reflect geographic nesting.
  • Examples:
    • State-level (2 digits)
    • County-level (5 digits)
    • Census tract-level (11 digits).
• Significance of FIPS Codes
  • Facilitates linking tabular data (e.g., population) to spatial data.

Importance of Data Familiarity

• Understanding dataset design and limitations avoids errors.
• Examples:
  • Familiarity with TIGER or USGS products is vital.

Common GIS Software Mistakes to Avoid

• Assume data capabilities without verification.
• Misinterpret attributes or spatial relationships.
• Fail to check for dataset updates or quality issues.
• GIS software does not review or validate map quality.

Responsibility for Accuracy

• Map creators are responsible for ensuring accuracy.
• Inaccurate maps can misinform and have real-world impacts.

Key Takeaways (General)

• Leverage reliable source datasets (use federal/state agency resources).
• Understand your data (limitations and intended use).
• Ensure maps are accurate and truthful (as the public often views them as factual).

This quiz explores the significance of accurate spatial data in Geographic Information Systems (GIS) and highlights advancements in data accessibility. It covers the evolution from physical maps to online resources and emphasizes the importance of verifying data sources before usage. Understand how local and state GIS repositories contribute to reliable mapping.