Propose and describe a new structure for the repo.

Author: ehrenfeu

README.md

@@ -12,3 +12,56 @@ Upon the first discussion, this would be something like:
 * National name
 
 More details on the related wiki page: [Catalogue of INT Charts](http://wiki.openseamap.org/wiki/OpenSeaMap-dev:Catalogue_of_INT_Charts)
+
+# IHO Publication S-11 and structure
+
+Many (all?) of the above details can be found as PDF documents provided by the
+IHO as [PUB S-11](http://www.iho.int/iho_pubs/standard/S-11/S-11.htm) in *Part
+B*. The structure of this repository therefore reflects the one currently given
+by the IHO.
+
+## Structure of `IHO_PUB_S-11`
+
+This is the top-level directory containing all the chart information. Its
+contents are described in the file `0_INDEX.csv` that corresponds to the table
+on the IHO website. It therefore contains exactly three columns:
+
+* `File` - the region name (e.g. *Region F*).
+  * Each entry reflects the name of a sub-directory that is located within
+  the top-level directory. Those will be referred to as the "*Region
+  directories*" below.
+* `Area` - the region's description (e.g. *Mediterranean & Black Seas*).
+* `Comment` - the last update (e.g. *Edition 2.0.4 - December 2012*).
+
+## Structure of *Region* directories
+
+Each directory is required to have a `0_INDEX.csv` file of its own. They have
+exactly two columns:
+* The index number:
+  * An internal number assigned by the OpenSeaMap project that corresponds to
+  the sequence of sections listed in the different Region PDF files.
+  * The number corresponds to a file of the same name (appended by the suffix
+  `.csv`), further down referred to as the "*Section*" files.
+* The section name:
+  * The (english!) name of the section as given in the PDF. Examples:
+    * *FROM COASTS OF THE CHANNEL AND OF THE NORTH SEA TO ICELAND*
+    * *WESTERN ENGLISH CHANNEL*
+  * This is purely descriptive (a "human readable name") and not reflected in
+  any file or directory name.
+
+## Structure of *Section* files
+
+The *Section* CSV files directly correspond to the tables in the various
+*Region* PDF files. They contain 11 columns with the content as follows:
+
+* INT No.
+* Prod.
+* National No.
+* Title
+* Southern limit
+* Northern limit
+* Western limit
+* Eastern limit
+* Date
+* Scale
+* Lat