My son, the land surveyor, revealed to me why many of the long tangents are on 19th century 'roads in areas sparsely populated at the time.
Imagine you've got the job, your transit (I hope that's the name for that telescope mounted in a u-shaped frame arranged to allow precise vertical motion thru 180 degrees of rotation, mounted on a tri-pod), and a couple of rodmen.... who's been told to start here, go there.
At "here" you aim your scope at "there" and put a rodman's staff at "here."
The other rodman walks out and plants his stick on the way to "there."
You walk out to the "there" staff, plant the transit, flip the scope and get a bead on the "here" rod, flip the scope over 180-degrees, and send the rodman with the "there" rod out again to plant it.
Repeat, repeat, repeat, 'til you get to "there."
Piece of cake!