I can figure a string line, but if you are using a 500 foot string line and you are even off by 1/2, that will end up being in a completely different part of town or on someone’s property by the time you are done. Do they just guesstimate and then when they see they are coming off they make curves or adjustments in the road? I know most roads arn’t straight, but the process still fascinates me.
In: 90
They use a tool called a theodolite, which is used in land surveying and allows you to measure both horizontal and vertical angels. The Theodolite has a telescope on it that pivots in 3 dimensions, and allows you to measure in very precise amounts the angels being marked. You can also determine elevation with this tool.
When you setup the Theodolite, it comes with a plumb that allows you to level it, then Someone else carries a sighting point (a big stick with a target on it), and the person using the theodolite directs them were to mark off the location on the ground.
Or….today they use GPS.
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