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ESRI ArcInfo Coverage Files are also known as simply as Coverages and less commonly as ADF files.
Coverages are made up of a set of files within a folder. The folder itself is the coverage name. The files roughly represent different layers, usually representing different types of topology or feature types.
> ls /data/coverage/brazil aat.adf arc.adf arx.adf bnd.adf lab.adf prj.adf tic.adf tol.adf
A folder with the name INFO is also part of the coverage. It sits at the same hierarchical level as the coverage folder itself. Therefore, to copy a coverage (using regular file system tools) the coverage folder and the INFO folder must both be copied. The INFO folder holds some catalogue information about the coverage.
> ls /data/coverage/info arc0000.dat arc0001.dat arc0002.dat arc.dir arc0000.nit arc0001.nit arc0002.nit
The directory is the data source. Layers are found within the directory. Using ogrinfo on a coverage directory:
> ogrinfo /data/coverage/brazil -summary INFO: Open of `brazil' using driver `AVCBin' successful. 1: ARC (Line String) 2: CNT (Point) 3: LAB (Point) 4: PAL (Polygon)
Using ogrinfo to examine the structure of a layer:
> ogrinfo /data/coverage/brazil PAL -summary Had to open data source read-only. INFO: Open of `brazil' using driver `AVCBin' successful. Layer name: PAL Geometry: Polygon Feature Count: 1 Extent: (1272793.274958, 795381.617050) - (1287078.382785, 807302.747284) Layer SRS WKT: (unknown) ArcIds: IntegerList (0.0) AREA: Real (18.5) PERIMETER: Real (18.5) F_OPER#: Integer (5.0) F_OPER-ID: Integer (5.0) OPER: String (2.0) FCODE: String (10.0)
Map File Example:
LAYER NAME Brazil_bounds TYPE POLYGON STATUS DEFAULT CONNECTIONTYPE OGR CONNECTION "/data/coverage/brazil" DATA "PAL" CLASS NAME "Brazil Admin Areas" STYLE OUTLINECOLOR 153 102 0 SIZE 2 END END END