Downloading and Using Datasets

Frequently Asked Questions

I have trouble downloading large datasets, PDF files, etc., what am I doing wrong?

When simply clicking on a link fails to get you the result you wanted, it is often useful to try right-clicking on the link and choosing "Save link as" or similar option. You will be asked to specify a particular place and file name to save the file on your hard disk. Once the download is complete you can either choose the "Open" option or browse to where you directed the file to be saved and double-click it there. Although it takes a couple more steps, this approach separates the download process from actually opening the file and is especially helpful with slow internet connections, large files, or files of a type unfamiliar to your computer.

I don't have the dBase program, how can I read dBase (*.dbf) files?

File whose names end in ".dbf" store data in a format first created for the dBase program. While that database program is no longer available, its early popularity means that most spreadsheet and database programs can read and write in this format, including Microsoft Excel and Access.

What are shapefiles and how can I use them?

Shapefiles are a way to store map features, characteristics, and associated attributes, the default format for ESRI's ArcView program. The information is actually stored in a collection of four or more files, all with the same first part to the name but with different filename extensions. Because all the files are needed as a group, they are often offered together in a compressed archive format that ends with a "zip" filename extension. This requires Winzip or some similar decompression program to "unzip" the archive into its original separate files. They should all be placed in the same folder. Note that the file that ends in the extension "dbf" contains attribute information for the objects in the shapefile. This is an ordinary dBase file and can be read by most spreadsheet or database programs.

What are coverages or export files and how can I use them?

"Coverages" refer to another way to store map information, this one favored by ESRI's ArcINFO and ArcGIS programs. The format is even more complicated than shapefiles. The information is stored in multiple files all stored in a folder whose name corresponds to the name of the coverage. What complicates this format is that essential information to use this coverage is also stored in files in a folder named "info" that is stored next to the coverage folder, and which may contain information on other coverages in that same workspace. To transport all the necessary information, ArcGIS or ArcINFO provide utilities to create an "export" file. You will need a copy of ArcGIS or ArcInfo, or some other GIS (geographic information system) program to translate the information back into its usable form as a coverage.

So how can I make maps using shapefiles or export files?

The export and shapefiles can be viewed using ArcGIS, ArcInfo, ArcView, or ESRI's free downloadable program called ArcExplorer. Many other geographic information systems can read or import these formats as well.

modified: 5-MAY-2005
created by: John M. Pye

Home | Contents