[MetaCRS] "FOSS Maintained" Source of CRS Definitions

[Martin Desruisseaux]

Mateusz Loskot a écrit :
> IMHO, the first thing would be to define common data model for all types 
> of definitions and their sources. XML, text files, db tables, etc. are 
> just physical representation of a model. If there would be a data model, 
> then, I believe, it was possible to use any type of storage you can 
> think of.

There is already an existing model, which is an international standard approved 
both by ISO and OGC: ISO 19111. Would it be an acceptable model?


>> There is already a "standard" and open format for CRS definitions,
>> namely WKT, correct? Couldn't this be used?

It can be used for "minimal" CRS definition. But the OGC standard WKT can not 
express Bursa-Wolf parameters targeting any other datum than WGS84, and can not 
contain useful metadata like area of validity. Yet it still applicable when 
there is nothing better. But when a choice is possible, I rather push for the 
EPSG database.

Note that WKT and EPSG database are not exclusive, and for those who don't want 
to support the EPSG database we can translate automatically EPSG entries into 
WKT entries. GeoTools among others already do that (can read an entry from the 
EPSG database and reformat as WKT).


>> At any rate, maybe there is already some type of "single source" for CRS
>> definitions already in existence. But I thought it didn't hurt to ask.

As far as I known the EPSG database is the most widely accepted at least at OGC. 
Some other sources like the PostGIS "spatial_ref_sys" table are actually 
generated from a subset of the EPSG database.


> - CRS model spec.

ISO 19111 ?

> - CRS interface spec. (not necesary but would be nice)

GeoAPI ?

	Martin