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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.
Tim Lewis
Narberth, Dyfed, UK
At sea, the Romans used the North Star for direction, but on land, a series of beacons and a surveying instrument called a groma, comprising a staff with four plumb lines, were used.
Having set a beacon in Chichester, the surveyor would head off towards London, find a high point where the beacon could still be seen, set another beacon, and…
