How did Roman road builders know which way to go? If they were a few degrees out setting off from, say, Chichester, they could have ended up in what is now Slough, not London. (continued)
Bryn Glover
Kirkby Malzeard, North Yorkshire, UK
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I have seen demonstrated, albeit on a small scale, a technique said to have been employed by Roman road engineers. Before constructing Stane Street, they would have had a good idea of the general direction to get to London or Chichester from either end.
They sent out teams of soldiers (of which they had thousands) along the guessed alignment from each starting point, so each team could see the flag held up by the teams either side of it.
Each team was equipped with pairs of simple aligning rods. They would sight on the flags, seeing an obtuse angle (90° to 180°) and a reflex angle (180° to 360°) between them. The soldiers would then move sideways in the direction of the obtuse angle, and so on. Eventually, the teams would shuffle themselves into a straight-line orientation.
Where difficult features such as rock outcrops or river confluences happened to coincide with the final line, the engineers would deliberately move the alignment to miss such features and order new shuffles to find the new shortest route.
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