[postgis-users] same well known text definition, but different SRID

[Jean-Denis Giguere]

Hi list !

I have to store data in postgis within the Canada Lambert Conformal 
projection (CANLAMB-83). There is only one CANLAMB-83 definition in my 
spatial_ref_sys but there are 7266 srid with 7266 dirrents auth_srid. 
The srid start at 104306 and stop at 11571. Each have the same auth_name 
USER.

Why is there as much srid for the same definition ? Is there a hidden 
difference between them ?

Is it a good idea to keep only one of them and delete all others row ?

I don't know how to prevent different users to create geometry in the 
same spatial reference system, but with different SRID.

Thank you,

Jean-Denis