I assumed the post title meant nanometers. Why? Floating-point rounding bugs. A nanometer is about 9e-15 degrees of latitude, which is right about where a double-precision floating point number runs out of digits. So, if a piece of software uses exact `==` equality, it could easily have a bug where two positions 3600 nanometers apart are seen as being different, even though they should be treated as the same.

I assumed nanometers.

I see it every day in chip/design/a few others. I was confused how I caused an issue with the points being so close.

I only realized NM means nautical miles only due to these comments.