PPT Slide
If the star of North by Northwest had gone to Penn Station and take the Pennsylvania Railroad’s Broadway Limited, the distance would have been 907.7 miles (again known to within a few 1/10 ths of a mile).
Suppose you were asked what the distance is between New York and Chicago by train. There is a substantial uncertainty introduced by the choice in route, and there are other routes, besides.
One reasonable solution would be to quote a number with an uncertainty: “…940 miles, plus or minus about 30 miles.”