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ArcGIS: An Introduction: Spatial Data

Tutorial for WICshop on ArcGIS

Geospatial data on the internet

This column lists a few top resources for geospatial data on the internet.  See tips on finding spatial data at "Locating spatial data." Please also feel free to get in touch with your data questions. 

United States Data Resources

Global Data Resources

See an extensive listing of resources by country at the International GIS Data Research Guide

Locating spatial data

Where does spatial data come from?

Type of Producer   Example
Government agencies USGS
Inter-governmental organizations United Nations Environmental Programme
Researchers and research centers U.S. Congressional District Shapefiles
Non-profits World Resources Institute
Private companies SimplyMap


Where can you search for spatial data?

Type of site
Library research guides International GIS Data
Government portals
Open data sites
Google Try searching for your topics, plus "shapefile" or "spatial data"

Spatial data models


Vector data represent discrete features, which could have names or attributes. It is often used in social science research to describe things with clear boundaries. Vector features can be of three types:

Point: A single pair of coordinates, like a cell phone tower or a crime scene
Line: Something that has length but not width; often a road or a river
Polygon: An area with boundaries; often a political feature such as a state or county, but could also be a lake, building footprint, etc.

 Common formats: shapefile, KML or KMZ,GeoJSON, MIF, GPX

Examples: Census TIGER Products

Example of raster dataRaster data represent continuous features as cells (pixels) in a grid, much like image files in which each pixel has a location in space plus a meaningful value. Raster files are frequently used in scientific studies for phenomena like rainfall, elevation, or things that vary continuously in space.

The level is detail is expressed as the cell size, or spatial resolution.

See What is raster data?

Common raster file formats: TIFF, Esri GRID, IMG, and others

Examples: National Elevation Dataset

Attribute data are not really a separate kind of data, but rather the fields (numeric or text) that can be joined  to features. The columns in the table become the attributes of the geographic feature to which it corresponds.

The trick is finding a unique identifier common to the features in the shapefile and the rows in the table. Common identifiers include FIPS (for the U.S.) and ISO-3166-1 (for countries).

Common formats: ArcGIS can join together geographic data like shapefiles with tabular data in formats such as .xls, .mdb, .txt, or .csv, using the Join tool.

Examples: Census 2010 Data

A gazetteer is a geographical dictionary that frequently lists placenames along with identifying information. While not necessarily in digital format, gazetteers in machine-readable formats like CSV, accompanied by latitude and longitude, can be converted to spatial data using the Add XY Data tool in ArcGIS.

Example: GeoNames

Web services provide a live connection to a remote databases via GIS software, without downloading the data to your local system. Different varieties of web services allow different capabilities for working with the data.

To use web services in ArcGIS, you must connect to the service via the Catalog window.

Example: ArcGIS Online

Geodatabases are a way to store collections of datasets in one location for use in ArcGIS. They can contain vector and raster data, as well as tables and other kinds of files.

Tools for converting between file formats