Different dimensions in board view and gerber

[Anonymous]

Hi forum,

I am using EAGLE 9.6.2 premium version. I have 2 polygons drawn in the board view. The separation distance between them is 2.5mm in the board view, but when I generate the gerber files and check, the separation distance is 2.35mm

picture 1: eagle board

picture 2: gerber file generated by EAGLE

Why is there a change in dimensions between the board view and the gerber file? 

Are there any settings that I'm missing out on?

Any help would be appreciated.
Thanks and regards
Nikhil

[one-of-the-robs · Accepted solution]

Your assertion of 2.5mm spacing on the board view is based on the properties of the polygons, namely the coordinates of the parallel lines.

Your 2.35mm spacing on the Gerber is measured between edges.

These are not the same thing! Look at the other properties of the polygon - it has a "width" of 0.1524mm. The coordinates of the lines are for the centre of the line. When you measure from the edges you're reducing that by the width of the line.

[Anonymous]

Hi @one-of-the-robs,

Thank you for the clarification on the coordinates and the edge-to-edge measurement.

Got my design working.

Regards,
Nikhil