thx I had seen before but don't refind it : Syndrome of the The Purloined Letter. by. Edgar Allan Poe :D

So If I have good understand
With a "Kilometer" unit "best" maximum precision can be the meter? :)
You say 5000 units max so 2500 "grid section" or admit 5000 "grid section"?
because in previous post you say -5000,+5000
so 2500 kms or 5000 kms with "snap size" 0.001:it is yet not so bad!