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Acquiring GIS Data: Utah |
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ESRI coverage:
The .e00 on each of the files you just downloaded lets you know: 1) that the file is an ESRI coverage, 2) that it has been exported by Arc/Info and 3) that it currently exists in an interchange file format. (We’ll cover import and export later)
An ESRI coverage is a combination of system directories and associated sub-files. If we take a look at the following screenshot of Windows Explorer we can see the relationship of an ESRI coverage before it is exported and how it is stored on the computer.
Results: ( win_explore_coverage )
In the above screen shot, you see a system directory called geog3560 along with several subdirectories. The active directory is index_250 and the files are shown to the right for this directory. There is a subdirectory under geog3560 called info, this directory maintains information about all the coverage’s in the workspace geog3560.
The importance of understanding this relationship is crucial when moving, copying or deleting an ESRI coverage. The file index_250.e00, that you downloaded, when imported, will create a system directory called index_250 and place all the associated files in that directory. It will then create, if it does not already exist, an info directory and place all the necessary links and associations there as well.
Thus, an ESRI coverage exists in a workspace (geog3560) and is made up of an (info) subdirectory and a system directory, which is also the coverage name (index_250). After importing or creating a coverage any associations between the two system directories and their files are reestablished.
If someone was to copy only the index_250 directory, the link/association between it and the info directory would be lost and the coverage would be corrupted. Once an ESRI coverage exists in this format, it is critical that all the associated directories and files stay together in the appropriate workspace.
To move or copy an ESRI coverage one of the following methods should be used to maintain the file structure integrity:
1) Export to an e00 interchange file then copy and paste as need, then import 2) ArcCatalog copy and paste 3) OS function, equivalent to ‘xcopy’ that will keep all subdirectory structures intact. 4) ArcInfo copy or copyworkspace command
These procedures will not be covered in this exercise but you must realize that there is an appropriate method to moving GIS data.
Questions: Using the following link ( win_explore_coverage )
What is the name of the workspace?
How many ESRI coverages exist in this workspace?
What would happen if the ‘info’ directory was deleted?
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