I have this line at the beginning of a Gerber file generated by Altium.


According the the Gerber Spec, the FS parameter should be followed by <L or T><A or I>. Nowhere does it mention the meaning of the D. Surely this isn't a bug in Altium.

  • \$\begingroup\$ I can't replicate this behaviour. What gerber export parameters/Altium version are you using? \$\endgroup\$ Dec 15, 2011 at 11:11
  • \$\begingroup\$ Annoyingly, I'm at a different desk at the moment. I'll have to wait until I get back to my PC before I can check. \$\endgroup\$ Dec 15, 2011 at 17:24

1 Answer 1


The "D" indicates a decimal coordinate format rather than the integer format assumed by the alleged specification you linked to, which seems not to cover all features in the, shall we say "living language".

What your board house can support is between you and them; if there's an issue first recourse would be trying options in the output menu to get an integer format, next would be reprocessing the data with your favorite string-processing language (even sed would probably do). In either case you probably want to do some manual verification that the interpretation is as expected the first time around.

For example, here's a few lines snipped excerpted from a file I found with a google search for occurrences of your format string (source http://homecinepc.free.fr/bassm/serigraphie.ge4)



For comparison, here's some lines from an "integer" gerber from an old project of mine:


  • \$\begingroup\$ Two things: 1. If that isn't the proper Gerber spec, then where can I find it? 2. The 'D' is supposed to mean I should expect decimal places in my coordinates. However there are none. Worse, in an arc command, the I and J have zeros omitted, but there's no way to tell if it's leading or trailing! \$\endgroup\$ Dec 15, 2011 at 10:41
  • \$\begingroup\$ My board house doesn't have a problem with the files. However, I am trying to write a program to solve this problem: electronics.stackexchange.com/questions/23085/… \$\endgroup\$ Dec 15, 2011 at 10:43
  • \$\begingroup\$ @Rocketmagnet no idea where to find a more complete spec. You are going to need to post a meaningful excerpt of your file before anyone can help you with its oddities. Usually one can figure out what a gerber file intends, especially with reference to knowledge of what it is supposed to look like. \$\endgroup\$ Dec 15, 2011 at 14:29
  • \$\begingroup\$ I'll post an example. The format document I linked to should be the definitive one, as Ucamco now own Gerber Systems Corporation. If people have been adding to the format, they seem to have been doing it outside of the official spec. \$\endgroup\$ Dec 15, 2011 at 15:19

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