[postgis-devel] st_isvalid() does not return warning message

[Mark Cave-Ayland]

Blake Crosby wrote:

> Maxime,
> 
> Thanks, perhaps I will upgrade!
> 
> So it looks like there is an issue with significant digits, in my view:
> 
> (-108.616666666667 54.2) != (-108.616666666664 54.1999999999825)
> 
> Cause it looks like its rounding up. and treating these two points as one.
> 
> Blake

Alas this is a general problem with floating point numbers, not just 
PostGIS - you only get 15-16 significant figures precision within a 
64-bit double :(

Even if you could rewrite PostGIS to use doubles > 64-bit, you'd still 
need to find suitable hardware support otherwise all floating point 
calculations would be terribly slow...


ATB,

Mark.

-- 
Mark Cave-Ayland - Senior Technical Architect
PostgreSQL - PostGIS
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