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Date: Tue, 29 Jan 2013 01:02:07 +0100
From: Gabriel Paubert <paubert AT iram DOT es>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] Export rounding
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On Tue, Jan 29, 2013 at 08:44:59AM +1100, Stephen Ecob wrote:
> On Tue, Jan 29, 2013 at 8:00 AM, Russell Dill <Russ DOT Dill AT asu DOT edu> wrote:
> > I'm submitting a board that I did with gEDA PCB in metric. The export to
> > imperial has caused some issues. The drill file and gerber files apparently
> > round to a different number of decimal places and it causes the drills to
> > wander in relation to copper.
> >
> > In my case, I have holes with 5 mil annular rings, which are my process
> > minimum, those minimum are now violated in my exported data. Has anyone else
> > run into this issue before? Have you been able to do anything to solve it?
> >
> > http://i.imgur.com/7arfVAK.png
> 
> Yes, I've experienced the same problem.  For my board it was annoying
> but not a show stopper as no design rules were violated.
> I guess that a very small code change would increase the drill
> resolution to the same as the gerber resolution.

The trouble is that the Excellon format for inch is set in stone and defined 
as 4 decimal places, i.e., 0.1 mil resolution: 

	http://www.excellon.com/manuals/program.htm

And the Gerber prodcued by PCB is 0.01 mil resolution.

Metric Gerber produced by PCB use micron as the resolution for both
drill and photoplotter files.

	Gabriel