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
Data Access / Connection Method¶
CONNECTIONTYPE OGR must be used. The ability to use coverages is not built into MapServer.
The path to the coverage folder name is required.
The layer name (feature type) is specified in the DATA parameter
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