Coverage vs. Shapefile?

[Daniel Morissette]

Sean O'Hagan wrote:
> 
> Can someone explain what a coverage is with respect to a shapefile? Is it a
> different format? Is it simply a collection of shapefiles?
> 

Coverages and shapefiles are different things.

Shapefiles are ArcView's native file format and are usually composed of
3 files with the same basename and extensions .shp, .shx and .dbf. 
Shapefiles do not contain any topology... e.g. in a shapefile the shared
boundaries between 2 polygons are duplicated.
Also, ESRI has published the shapefile format specs so several
applications (like MapServer) can deal with shapefiles.

Coverages are Arc/Info's native format... every coverage comes as a
directory in which most of the files have a .adf extension, and the
attributes come in an info directory.  
Coverages can contain topology and thus allow you to do more advanced
analysis in Arc/Info.  You can open coverages in ArcView but I don't
think that you can take advantage of the topology in ArcView (but I
could be wrong).

I hope that helps!

P.S. The coverage specs are not published by ESRI, but have been
reverse-engineered...  :-)
	http://pages.infinit.net/danmo/e00/docs/v7_bin_cover.html
-- 
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 Daniel Morissette                       danmo at videotron.ca
              http://pages.infinit.net/danmo/
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  Don't put for tomorrow what you can do today, because if 
      you enjoy it today you can do it again tomorrow.