Data Import

Introduction to Geographic Information Systems in Forest Resources

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Data Import

Discussion:

You have already seen how to download and import grid data from USGS-format Digital Elevation Models (DEMs).

You have already seen how to create point themes from tables or text files containing X and Y coordinates.

Now you will learn to deal with another common interchange format. ArcInfo has been the de facto industry leader in GIS software, so many organizations that have built GIS databases have used ArcInfo. Therefore, a large amount of GIS data exist in ArcInfo format. Data from ArcInfo are most commonly distributed in the ARC Interchange File format, also commonly called the ARC Export File, or the e00 ASCII format. These files can be imported using the Import or Import71 programs in the same place where the ArcView shortcut is located.

What are ARC Interchange files?

ARC Interchange Files are used to transfer ArcInfo data across multiple file systems, across multiple computers, and across multiple computer architectures. Because of the complexity of the ArcInfo file storage model, it is necessary to export data sources from ArcInfo before they can be imported to ArcInfo or ArcView running on other systems.

The ArcInfo workspace file storage model works as indicated in this diagram. In this example, the workspace jasper contains data sources for the themes water, soil, elevatin, and vegetatn. These directories contain coordinate and geometry data files for each individual theme.

For each ArcInfo workspace, an info directory exists containing all tabular data for the themes, including theme attribute tables, boundary, and tic location tables. Without both theme directories and the info directory, the workspace or themes will not function.

The EXPORT command in ArcInfo exports a theme's directory and any tabular data from the info directory associated with that theme. This results in a single interchange file that will completely recreate the theme when imported.

ARC Interchange files always have the file extension .enn, where the nn is the number of the individual part of the interchange file. A single coverage, grid, or TIN can be exported into an interchange file that spans multiple files. This option can be used to save an interchange file in parts on several floppy disks. Now that floppy disks are on their way out, supplanted by either the Network or by larger removable devices, such as Zip and Jaz media, you will almost always encounter single interchange files, with an file extension .e00.

Importing ARC Interchange files

The interchange files are created on a machine running ArcInfo, and then moved to another system, and imported. Frequently data available on the web and are posted in this format. You can download these interchange files and save them on a place in your local file system.

In this case, I have downloaded the Railroads Interchange file from the Pack Forest GIS page, which represents railroads within the vicinity of Pack Forest..

Using the Import71 executable, supply the filenames necessary to import the data set. The Export Filename is the full pathname to the e00 file that came from another system. The Output Data Source is the full pathname to the theme to be created. In this example, I am creating a theme called rr2 from the interchange file rr2.e0, both in the C:\temp directory. If you attempt to create a new ArcInfo coverage (Output Data Source) that has the same name as an already existing file or directory, you will get an error (e.g., if you only specify the Output Data Source C:\temp).

When the file is imported, it can be used as a theme.

When the Import71 utility is used, it recreates an ArcInfo data set with the same workspace described above. Importing also creates an info directory storing the attribute tables. If you wish to store this as a shapefile, you need to use the Convert to Shapefile operation in ArcView.

Syllabus	Schedule	Class Meetings	Assignments	Course Data	Internet Search
Current Grades	Contact Us	CFR 590	Internet-only section	Lab Locations

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