Frequently Asked Questions (FAQ) about Geographic Information Systems (GIS)

GIS stands for Geographic Information Systems. The main software package is called ArcGIS and is supplied by the Environmental Systems Research Institute (ESRI). A good place to start learning more about the potential applications of GIS in demography and the social sciences is ESRI’s home page. In addition, you can find a staggering amount of information about GIS on the Internet, including software training and tutorials, data products, statistical techniques, and myriad areas of application (crime, health, planning, etc.).

Geospatial data store the geometric location of a particular feature or object (represented as either a point, a line, or an area), along with attribute information describing what those features represent. Geospatial data may come from a variety of sources—individual, household, or institutional surveys; population censuses, land use surveys, human infrastructure databases (streets, buildings, business listings, tax records, etc.), satellite imagery, aerial photographs, and paper maps. It is commonly reported that over 80% of all data are geospatial—that is, these data can be linked to features or objects such as a street address, a census tract, a ZIP code, a school district, a police precinct, a health service area, a county, a state, and/or a country.

Formats readable by spreadsheet or statistical software (and, of course, ArcGIS shapefiles) are the most directly useful; however, it may be possible to use other types of files. With ArcGIS, the preferred tabular data format is .dbf. If you have data for specified geographic areas (e.g., counties or census tracts) in Excel, ASCII, or other formats, such as SAS, the data can be easily converted to .dbf format, and can usually be integrated with other geospatial information quite easily.

Census data and boundary files for various geographic levels are the most commonly used data. However, many other datasets are available. Please see the Spatial Data page, which contains a more detailed listing of available resources. Additional datasets are also available from SodaPop, although not all of their datasets have a geographic component. The Geographic Levels and PRI Data Archive page lists available datasets by geographical levels.

PRI currently has files at a variety of geographic levels : nation, region, division, state, county, tract, block group, place, ZIP code, MSA/CMSA, PMSA, urban area, congressional district, American Indian, ANRC, MCD, and block.

The best source is the DIVA-GIS website. Please contact the GIA team for further assistance.

You can combine datasets when they contain (a) different areas with records at the same geographic level (e.g., appending records for Alaska and Hawaii to records for the 48 contiguous states to produce a complete dataset of all 50 U.S. states) or (b) additional data for existing records at the same geographic level (e.g., adding environmental data such as average temperature for a county to the census data for a county).

Yes, we can scan maps and images and then convert them into a format that ArcGIS can use. This process may take time, depending on the complexity of the original map and the clarity of the image.

You should store data in your personal webspace or space allocated for a project. Or you can store your data on removable media such as a flash drive. Geospatial datasets can be large, so please adopt sound data management practices. Also, it is advisable to back up all project data on a regular basis.

ESRI has made a number of changes in the new version of ArcGIS Desktop. These changes include new spatial statistics tools, improvements in annotation and labeling, improved raster support, and new geoprocessing tools. A more detailed list of new features in ArcGIS 10.3 is available from ESRI.

You can think of a project file as a database management tool. GIS users often must work on the same files for long periods of time, and the .mxd file is the management file that remembers which files you use, where they are located, the projection the file is stored in, the colors you have set, etc.

Once you open your project file, editing is simple. The last saved version of your files will appear on your computer screen, and you can manipulate the existing settings to update the file. (Always remember to save it!) Project files must be edited in order for changes to be reflected in your work. You’ll often work on GIS projects over long periods of time, and as you work, new data, shapefiles, etc. can be added to keep your project current.

Shapefiles are computer files that produce images for users in a GIS environment. There are three basic types of shapefiles:

  • Polygons (area-based features such as census tracts and block groups)
  • Points (address locations)
  • Lines (roads, rivers, etc.)

Several affiliated files must be together for a GIS system to use and present the data. Some common file types are .shp, .shx, .sbn, and .dbf. When you are downloading shapefiles from data sources, there may be other affiliated files; make sure you have all files with the same name in the same directory when using them.

Address matching in ArcGIS is simple once you have worked with this type of data a few times. To address-match, you need a .dbf file of address information that includes the street address and preferably the ZIP code of your locations of interest. It is possible to address-match with just a street address, but in large urban areas a common street name (e.g., Main Street or 17th) may appear across several ZIP codes, making the address-matching process a more difficult and time-consuming task. As with so many tasks, address-matching accuracy is only as good as the skills of the person doing the work.

If you have data with spatial locators (e.g., census FIPS codes, ZIP codes, street addresses), you can link your data to shapefiles within a GIS environment. You also can join tables in a GIS project.

ESRI makes additional ArcGIS functionality available through the use of extensions. Extensions allow you to add specific features to the software as necessary and then unload this functionality when you no longer need it. The full list of available extensions, with descriptions of each, is available here.

ArcMap is the application in ArcGIS that you use to create, visualize, and manipulate maps. ArcCatalog is the application in ArcGIS for browsing and organizing data files. ArcToolbox is the application in ArcGIS that contains data management and conversion tools and wizards (e.g., projection tools).

The Spatial Analyst extension can help you find slopes and directions, least-cost paths, and best locations for a new facility based on multiple criteria. This is useful for analyzing raster data as well as feature data.

The Geostatistical Analyst extension can help you with the production of statistical surfaces for exploratory spatial data analysis, structural analysis (calculating properties of neighboring areas), and surface prediction and results analysis.

ESRI has a number of scripts and other downloads available. Scripts work with the existing software to extend functionality or to automate common tasks. The scripts on ESRI’s site come from ESRI itself and from other ArcGIS users; you can even upload your own scripts for other people to use.

An .E00 file is an ArcInfo interchange file that contains spatial feature information and attribute data in a fixed-length ASCII format. You use these files for the system-independent exchange of GIS coverages and associated data. To work with data in this format in ArcGIS, you must first convert it using ArcToolbox : In the ArcToolbox window, click the plus signs next to Coverage Tools, Conversion, and To Coverage, respectively. Next, double-click “Import from E00”. Under “Input Interchange File,” navigate to the file want to convert. Specify the output dataset and click OK. The resulting output file(s) will be compatible with ArcGIS. News Honor a Colleague Letter for Suet-ling Pong Steffensmeier named Liberal Arts Research Professor Postdoctoral Training position in Family Demography and Individual Development: NOW ACCEPTING APPLICATIONS Spatial demography publication explores new practices Life as an immigrant inspires College of Education faculty member's book Really Big Data Penn State symposium aims to reconstruct African-American narratives Van Hook Wins Raymond Lombra Award De Jong receives the College of the Liberal Arts' Emeritus Distinction Award Penn State to host national symposium on African-American family issues