[postgis-users] General question about SRID and projection

[Nelson Guda]

Hi all,

This may be an ignorant question, but I am failing to understand  
something basic.  I hope someone can help me clear this up.

first, the SRID refers to the projection of your geometry, correct?   
If this is so, then is the geometry data in postgis stored as lat /  
long points or as projected coordinates?  If it is stored as lat /  
long, why does the SRID matter for any of the geometry functions?   
Shouldn't they all be performed on unprojected data?

If the data is stored as projected coordinates, then why is it  
suggested to convert SRIDs to -1?  Don't you then lose important  
information about the projection?

Also, wouldn't it be easier to have all of the geometry stored as  
lat / long data and deal with projection for output only?

Thanks all.  I've really appreciated this group.  It has helped me a  
lot in getting together my site on US roadless lands (http:// 
www.roadlessland.org ).

Best,
nelson