Precision for Real Comparisons

In the CompareDWG Preferences you can set the precision to be used for the comparison of real numbers. This determines when two real numbers are accepted as the same.
The precision is interpreted as the maximum acceptable difference.

For example, if you have a point in your Old Drawing at location 10.00, 20.00 and the same point is at location 10.01, 20.00 in your New Drawing then the comparison concludes as follows:

Precision Same location
0.0099 No
0.01 Yes
0.011 Yes

Choose a precision that is right for your business. If a two-digit precision is important for your work, then using a precision of 1E-5 for comparing will usually give good results. You may specify an extremely small precision, or even 0, but this will possibly give unexpected results. Even if you compare a drawing with itself, you may still find that differences are reported if AutoCAD finds that 1E-300 is not the same as 0. (This problem is not AutoCAD specific but occurs in all computer programs that use real numbers.)

If one of the files you compare has been stored in ASCII DXF format, then the real numbers in this drawing will have lost part of their precision. This depends on the number of decimal places used when the DXF file was written.
In this case it is particularly important to use a correct setting for your precision.

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