[Proj] Difference between same projections types

[support.mn at elisanet.fi]

Hello,

the two first definitions are self sustained but the 3. definition needs a
database where the definition is kept. The problem with the 3. type is
that if the organisation that makes these definitions adds new ones the
old system trops out.

The two first definitions are better since if new definitions are added
the old system can also use them (since all information is given in the
definition it self). If you use a database to keep the references you
need to update that all the time to stay updated if new entries are added.

BTW: this is exactly the problem with some definitions in geotiff
standard. Luckily most creators put all data to the geotiff file and discard
any database but there are users that use the database. New version
of the standard should freeze that database and forbid adding new
entries to it and so force the use of the full definition at least for the
new entries. That would then stabilize the geotiff standard.

Regards: Janne.

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Mustafa646 [noorcs22 at gmail.com] kirjoitti: 
> 1.  (+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs )
> 2. GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS
> 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AUTHORITY["EPSG","4326"]]
> 3. EPSG: 4326
> And what is the difference between these 3 types.
>