Chapter 7: Digital Data

What is the approximate number of search results for “GIS data download” or “dem srtm”?

About 300 million

What are examples of free digital data types?

Vector, raster, and georeferenced graphic data (e.g., Kauai datasets)

Why do national governments create GIS portals?

To provide official access to digital spatial data

Why is there no single global data clearinghouse?

Because data comes from diverse sources, themes, and standards

What are the best global spatial data sources?

United Nations, European Union, national governments, specialized projects (e.g., Natural Earth)

What datasets does NOAA provide?

Shoreline, estuarine bathymetry, and climatic/environmental data

What are examples of ESRI’s data portals?

ArcGIS Hub Open Data, Living Atlas, COVID-19 dashboards

What are examples of local GIS department sites?

Washington DC, Austin TX, State of New York, Los Angeles

What other organizations provide GIS data?

Engineering firms, land surveys, aerial photos, CAD drawings, universities, FEMA

What is a Digital Line Graph (DLG)?

USGS vector dataset with categories like PLSS, boundaries, transportation, hydrography; topologically structured

What is The National Map?

A USGS project providing seamless topographic data (elevation, orthoimagery, hydrography, boundaries, etc.)

What is USGS Earth Explorer used for?

Accessing DEMs, DOQQs, DLGs, DRGs, Landsat, LULC, SRTM, NAPP

What is the National Elevation Dataset (NED)?

High-resolution elevation raster data across the U.S.

What is LIDAR?

Light Detection and Ranging; provides accurate relief/elevation data (point clouds, DEMs)

What is the National Hydrography Dataset?

Surface-water features: lakes, rivers, streams, wetlands, hydrologic unit codes

What is orthophotography?

Aerial imagery corrected for distortion, ensuring uniform scale

What is a DOQQ?

Digital Ortho Quarter Quad: 1 m resolution, ~5 miles square, NAD83, UTM projection

What is NAIP imagery used for?

Annual agricultural monitoring and detecting land changes

What are some sources of remote sensing data?

USGS (ASTER, MODIS), NASA, ESA Planetary Science Archive

What are examples of USGS land cover datasets?

GLCC, LUDA, NLCD (National Land Cover Dataset, includes imperviousness)

What is CCAP?

Coastal Change Analysis Program; higher-resolution land cover data for U.S. coastal areas

What is SSURGO?

Detailed NRCS soil database; polygons represent uniform soil mapping units

What FEMA dataset is useful for disaster planning?

Floodplain maps

What are TIGER/Line files?

Topologically Integrated Geographic Encoding and Referencing; roads, rivers, railroads, census boundaries

What are FIPS codes?

Federal Information Processing Standards; unique identifiers for U.S. geographies

How does the CDC use GIS data?

Publishes datasets linked to U.S. census-recognized geographies

What does the U.S. Board on Geographic Names provide?

Authoritative place names (not maps)

What is User-Generated Content (UGC) in GIS?

Data from hobbyists and researchers (e.g., Robin Wilson’s free dataset list)

What is OpenStreetMap?

A collaborative, editable world map built from GPS, aerial photos, and local knowledge