Bill, I haven't read anything about that before. It could be that the Yanks relied on pre-war mileposts or information from citizens about actual distances, rather than measuring it themselves. All I know about the army engineers' measurement procedures is from a reprint of a booklet or pamphlet I have around here somewhere, dating from 1858 (I think) that lays out the procedures for measurements using a chain -- though it deals only with laying out a camp; also a reprint of a manual (from 1862) that mentions assigning the task of "pace counter" to a soldier in a column of troops.

I'll bet Tom Ezell knows something about this subject. Maybe he'll jump in and discuss it.

I just find the report very interesting, not only in identifying the routes that the roads took, but also the description of the river crossings, forage, etc., along the road.