On Sun, 2011-02-06 at 12:27 -0500, rickman wrote:
Parts should match the rest of a system I think. The dimensions of a
part can be stored in the units that best suit the system. It seems
silly to store a part as metric and let the system round it off to
inches on the fly rather than to do the round off when the part is
created. But that's just my opinion.
Conversely, to me it seems silly to deliberately loose information on
the part's original specification.
If the manufacturer specifies some dimension as 1mm, that is how it
should stay represented in our source design files, not 39.3700787 mils
(or however one chooses to round it).
PCB already supports reading units like 1mm in its input files, but it
always saves out the rounded imperial representation.
Sure - it probably doesn't matter if you round everything based on true
position when creating the file, but if the user were to copy+paste part
of that new (rounded) footprint using an imperial grid, to make a longer
part - rounding errors could easily be compounded.