[postgis-users] what does it really mean for one geometry to be equal to another

[Paul Norman]

On 9/15/2016 10:11 PM, Sandro Santilli wrote:
> you could create an index on
> ST_SnapToGrid(geom, <tolerance>), for points to be no closer
> than <tolerance>.

This won't check that points are no closer than <tolerance>, nor will it 
solve floating point issues. It's the same as rounding. If two points 
are on either side of the line where they round to different grid 
points, even if they are arbitrarily close, up to the limit of precision.

It does mean that you will see fewer values where you get floating point 
equality issues, but the difference between the rounded floating points 
will increase.