[postgis-devel] Re: [postgis-users] extent changed a little in rc3

[strk at refractions.net]

BOX2D output has been reverted to .15g precision.
--strk;

On Thu, Mar 17, 2005 at 10:12:40AM +0100, strk at refractions.net wrote:
> Bernhard,Mark
> I can take the box2d output back to .15g, but be aware that box2d
> uses single precision, not double, so the 1.0000001 would become
> 1.00000011920929, and not 1.0000001 as you would expect.
> 
> .8g would give it as written (for this specific case ;)).
> The python site you mentioned suggests 17, but I think they
> are referring to double precision, not single.
> 
> Currently the default is used, which is 6.
> 
> Give your numbers ;)
> 
> --strk;
> 
> On Tue, Mar 15, 2005 at 10:20:59AM -0000, Mark Cave-Ayland wrote:
> > Hi strk/Bernhard,
> > 
> > > -----Original Message-----
> > > From: postgis-users-bounces at postgis.refractions.net 
> > > [mailto:postgis-users-bounces at postgis.refractions.net] On 
> > > Behalf Of strk at refractions.net
> > > Sent: 14 March 2005 21:14
> > > To: postgis-users at postgis.refractions.net
> > > Subject: Re: [postgis-users] extent changed a little in rc3
> > 
> > (cut)
> > 
> > > > So, the upshot this is: I think it's better to report reasonably 
> > > > accurate values in the textual representations of postgis 
> > > types than 
> > > > trying to hide the effects of binary floating point.
> > > 
> > > You're probably right, it was a bad idea changing it...
> > > Anyone else's opinion on this ?
> > 
> > I think that reporting the accurate value is the way to go, as suggested by
> > the poster. My suspicion is that most people using PostGIS would already be
> > aware of the effect of floating point rounding errors, but I think I would
> > be surprised if my highly accurate data was displayed differently from its
> > actual value in the DB.... I would consider rounding to be something done at
> > the application layer if required.
> > 
> > 
> > Kind regards,
> > 
> > Mark.
> > 
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